Nieuws Lood en gezondheid


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Zware metalen - lood


Blootstelling van Dunedin kinderen aan lood in verband met lagere IQ

Extreem hoge niveaus van lood in Nieuw-Zeeland steden in de jaren 1970 en 1980 lijken verantwoordelijk voor een verlies van intelligentie en beroepsziektes onder volwassenen van vandaag. Het meest recente onderzoek van de Universiteit van Otago langlopende Dunedin Study Nieuw-Zeeland laat zien dat onder meer dan 500 kinderen die opgroeiden in het tijdperk van gelode benzine, die zijn blootgesteld aan lood een lager IQ en sociale status haden op de leeftijd van 38, ten opzichte van leeftijdsgenoten die aan minder waren blootgesteld.

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Lage lood waardes in kinderen hebben negatief effect op schoolcijfers

Een nieuwe studie die data uit een Rhode Island's onderzoeksprogramma en data van herhaalde loodtesten gebruikt laat zien dat een lage blootstelling
aan lood onder scholieren slechte leerresultaten kan voorspellen in de jaren die volgen. (Bron Brown University)

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Relatie tussen lood waardes en crimineel gedrag


Hoe een Amerikaanse stad vergiftigd werd met lood in het drinkwater


Blootstelling aan lood benvloedt de slaap van kinderen

Een nieuw onderzoek aan de Universiteit van Pennsylvania School of Nursing (Penn Nursing) laat zien dat blootstelling aan lood in de vroege jeugd een verhoogd risico geeft op slaapproblemen en overmatige slaperigheid overdag tijdens de latere kindertijd.

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Onderzoekers ontdekken bewijs dat blootstelling aan lood van moeders gevolgen kan hebben voor volgende generatie

Een team van onderzoekers aan de Wayne State University heeft ontdekt dat moeders met een hoog loodgehalte in hun bloed niet alleen de cellen van het ongeboren kind, de foetus, kunnen aantasten, maar ook die van hun kleinkinderen.

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Algemene methode om het loodgehalte van drinkwater te verlagen kan tegengestelde effect hebben

Nieuw onderzoek heeft aangetoond dat het verlagen van de pH van de gemeentelijke watervoorzieningen, een gemeenschappelijke strategie gebruikt om de vrijlating van oplosbaar lood uit sanitaire materialen te controleren, de corrosie van gietijzer kan benvloeden, wat resulteert in verhoogde niveaus van zowel deeltjes ijzer als deeltjes lood in drinkwater .

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Lood in het bloed van kinderen gerelateerd met gedrags- en emotionele problemen

Uit een onderzoek gefinancierd door het National Institute of Environmental Health Sciences (NIEHS), onderdeel van het National Institutes of Health, blijkt dat emotionele- en gedragsproblemen bij kinderen optreden zelfs na een lage blootstelling aan lood en de problemen erger worden naarmate het loodgehalte verhoogt.

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Bewijs voor effecten van giftig lood en crimineel gedrag

Als misdrijfcijfers dalen, geven politici zichzelf graag een schouderklopje voor hun strenge beleid. Maar er is een nieuwe theorie die steeds geloofwaardiger wordt en duidelijk maakt waarom het landelijke geweld sinds 1990 gedaald is, en het heeft niets te maken met het crimineel rechtssysteem. Een artikel in Chemical & Engineering News toont duidelijk de toenemende cijfers waaruit zouden blijken dat het verwijderen van lood uit benzine en verf een cruciale rol heeft gespeeld.

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Hogere gehaltes lood in bloed aangetroffen bij kinderen woonachtig in de buurt van gifbelten, met als gevolg een lager IQ

Een onderzoeker van Mount Sinai schat dat blootstellen aan lood geestelijke achterstand bij 6 op de 1000 kinderen, die in de buurt van zulke plaatsen wonen, kan veroorzaken. Kinderen die in de buurt wonen van gifbelten in landen met een laag en gemiddeld inkomen zoals India, de Filippijnen en Indonesi kunnen een hoger loodgehalte in hun bloed ondervinden en een hogere verbreiding van geestelijke achterstand, volgens een onderzoek dat werd gepresenteerd door Kevin Catham-Stephens, arts en pediatrisch mandaathouder voor Gezondheid en Milieu bij de Icahn Universiteit voor Geneeskunde van Mount Sinai, tijdens de jaarlijkse bijeenkomst van de Verenigingen van Universiteiten voor Kindergeneeskunde (PAS) op 6 mei jl. in Washington, DC.

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Zit loodvergiftiging soms achter jeugdcriminaliteit?

Lood treft men aan in oude verven (met inbegrip van die op oud kinderspeelgoed), in de bodem, in oude leidingen, in water, in de atmosfeer, in loodhoudende brandstoffen van voertuigen zelfs in drinkbekers. Bij hoge dosering is het dodelijk, maar veroorzaakt ook schijnbaar triviale symptomen zoals hoofdpijn. Bij kinderen leidt het ook tot schade aan de organen, de nieren in het bijzonder en het zenuwstelsel inclusief de hersenen.

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Lead in the Environment: No Safe Dose

Philippe Grandjean, adjunct professor of environmental health, discusses the findings of a report by the European Food Safety Authority (EFSA), which concludes there is no known safe exposure to lead.


Lood vergiftiging - Govt. gewaarschuwd Zamfara tienmaal

Tien verschillende brieven werden gestuurd door het federale ministerie van mijnbouw en staal ontwikkeling in de Nigeriaanse deel staat Zamfara om te waarschuwen voor de gevaren van illegale mijnbouwactiviteiten (vr het recente incident van lood vergiftiging die het leven van honderden kinderen eiste).

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Eric van Staalduinen


In Nigeria 163 doden door loodvergiftiging

In het noorden van Nigeria zijn sinds maart 163 mensen gestorven door loodvergiftiging als gevolg van het illegaal delven van goud.

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Lead Poisoning in Children

Pediatrician explains the frightening symptoms and permanent disabilities of lead poisoning in children. Besides lead paint, pesticides and other harmful chemicals in the home can cause similar serious and permanent health problems.


Kleine hoeveelheden lood kunnen de nieren van kinderen beschadigen

Kleine hoeveelheden lood in het lichaam van gezonde kinderen en tieners kunnen hun nierfunctie verslechteren. Ook als het gaat om hoeveelheden die ver beneden de toegelaten normen van de US-Centra voor Ziektecontrole en -Preventie liggen Dit meldt een studie van het John Hopkins Kindercentrum, op 11 januari in de Archieven der Interne Geneeskunde gepubliceerd .

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Nelly.Busschots


Bronnen van lood

- loden waterleidingen (oude huizen)
- loodhoudende verfsoorten in oude huizen
- benzine (tot 1984)
- sigarettenrook


Loden leidingen

Loden drinkwaterleidingen zijn verboden: als looddeeltjes in het water belanden, kunnen ze namelijk de gezondheid bedreigen. In de bouw zijn loden leidingen sinds 1960 al in de ban, maar in oudere huizen kunnen ze nog voorkomen. Lood is vroeger algemeen gebruikt voor drinkwaterleidingen. In de leidingen kunnen echter kleine metaaldeeltjes loslaten en zo in het drinkwater komen. De hoeveelheid lood die een volwassene binnen kan krijgen via drinkwater uit loden leidingen, ligt ruim onder de wettelijke norm; maar kleine kinderen zijn veel gevoeliger voor lood. Teveel lood kan leiden tot schade aan het zenuwstelsel (leerstoornissen), bloedarmoede, miskramen en aangeboren afwijkingen en nierbeschadiging. Zuigelingen die flessenvoeding krijgen met water uit loden leidingen, kunnen al snel een ongezonde hoeveelheid binnen krijgen. Dat kan schadelijk zijn voor de ontwikkeling van hersenen en zenuwstelsel: het kan leiden tot een wat lagere intelligentie (een tot vijf IQ-punten) en tot gedragsveranderingen. Eind 2006 moesten alle loden leidingen in huurwoningen, en negentig procent van de loden leidingen in particuliere woningen zijn gesaneerd.

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Lood kan een aantal ongewenste effecten hebben

- De verstoring van de biosynthese van hemoglobine en bloedarmoede
- Een verhoging van de bloeddruk
- Nierbeschadiging
- Miskramen
- Verstoring van de zenuwstelsels
- Hersenbeschadiging
- Afgenomen vruchtbaarheid bij mannen door beschadiging van het sperma
- Verkleinde leermogelijkheden bij kinderen
- Gedragsstoornissen bij kinderen, zoals agressie, impulsief gedrag en hyperactiviteit
Lood kan via de placenta van de moeder bij een foetus terecht komen. Daardoor kan het ernstige schade toebrengen aan het zenuwstelsel en de hersenen van ongeboren kinderen.

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Belangrijke informatie voor eigenaren van huizen die gebouwd zijn voor 1960

We hebben in Nederland - gelukkig - drinkwater van een zeer goede kwaliteit. Natuurlijk willen we dat zo houden. Daarom is het de bedoeling om voor 2005 alle loden leidingen te vervangen. Via loden leidingen komt er namelijk lood in het drinkwater. Hoewel lood in het lichaam voor vrijwel niemand risico oplevert, hoort het er niet thuis. De waterleidingbedrijven en het ministerie van VROM zullen hun steentje bijdragen om de lodenleidingen te vervangen. U kunt namelijk subsidie krijgen als u uw loden waterleidingen gaat vervangen. Er geldt een waarschuwing tegen het gebruik van water uit loden waterleidingen voor het aanmaken van (fles)voeding voor zuigelingen tot n jaar. Zij lopen een zeer beperkt risico. Voor oudere kinderen en volwassenen levert lood in drinkwater geen risico's op. Heeft u een huis van voor 1960 en vermoedt u dat uw huis nog (gedeeltelijk) lodenleidingen heeft dan kunt u voor meer informatie over saneren, subsidiemogelijkheden en gezondheid contact opnemen met:

Ministerie van VROM
loket sanering lodenleidingen
telefoonnummer (070) 3395107
op werkdagen van 8.30 tot 12.30 uur
internet: www.minvrom.nl


Lood en babyvoeding

Als poedermelk wordt aangemaakt met water uit een loden waterleiding, krijgt de baby lood binnen. De Gezondheidsraad adviseert bij aanwezigheid van loden waterleidingen bronwater in plaats van kraanwater te gebruiken voor de bereiding van flesvoeding. De baby loopt geen risico als het alleen borstvoeding krijgt. Ook niet als de moeder water drinkt uit loden waterleidingen.

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Vrouwen en lood

Vrouwen worden eveneens meer getroffen dan mannen, vooral tijdens een zwangerschap en in de menopauze: het lood vult immers de ruimte op van de ontbrekende voedingsmineralen. Mensen die lijden aan een tekort aan ijzer, calcium en zink zijn dus extra vatbaar voor loodintoxicatie.

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Lood

Sinds het bekend worden van de schadelijkheid van lood voor het milieu, is het gebruik ervan sterk teruggedrongen. Tot die tijd waren er legio toepassingen:

* De hoge buigzaamheid maakt lood geschikt om bij woningbouw kieren te dichten (loodslab). Van deze eigenschap wordt ook gebruikgemaakt in ramen van glas en lood, waarbij het stukje glas in een loden vatting opgesloten zit en de loodstrippen aan elkaar gesoldeerd worden.
* In oplaadbare batterijen en accu's wordt lood als elektrode gebruikt.
* In brandstoffen kan loodtetraethyl worden gebruikt als octaan verbeteraar. In de EU is dat sinds 1999 niet meer toegestaan.
* Lood kan worden toegepast in verf om het beter bestendig te maken tegen weersinvloeden. Sinds 1990 is dat in de EU niet meer toegestaan. Als pigment werd loodwit (loodoxide) veel toegepast.
* Legering met tin voor orgelpijpen.
* In de elektronica als soldeerverbinding in een legering met tin en soms ook zilver, (voorbeeld 60%lood, 38%tin en 2%zilver)
* In de legering Woodsmetaal voor diverse toepassingen.

Langdurige blootstelling aan lood en loodverbindingen kan hersenbeschadigingen veroorzaken en tot bijvoorbeeld dementie leiden. Om die reden is het niet meer toegestaan lood te gebruiken voor waterleidingen.

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Lood rapport

Gezondheidsraad: Commissie Lood in drinkwater. Lood in drinkwater. Rijswijk: Gezondheidsraad, 1997; publicatie nr 1997/07. ISBN 90-5549-159-4

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Blootstelling aan lood verdubbelt kans op manische depressie en vervijfvoudigt kans op angststoornis

Lead exposure was thought to be a thing of the past, but it is more common today than most realize. A recent study in the Archives of General Psychiatry (December issue) found that individuals with lead levels of 2.11 ug/dL or more had 2.3x greater risk of being diagnosed with Manic Depressive Disorder (MDD) and had nearly 5x the odds of panic disorder compared with those with lead levels of 0.7 ug/dL or less.

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Lead in kids


Blootstelling aan lood tijdens kindertijd veroorzaakt permanente hersenschade

A study using functional magnetic resonance imaging (fMRI) to evaluate brain function revealed that adults who were exposed to lead as children incur permanent brain injury. The results were presented today at the annual meeting of the Radiological Society of North America (RSNA). "What we have found is that no region of the brain is spared from lead exposure," said the study's lead author, Kim Cecil, PhD, imaging scientist at Cincinnati Children's Hospital Medical Center and professor of radiology and pediatrics at the University of Cincinnati College of Medicine. "Distinct areas of the brain are affected differently." The study is part of a large research project called the Cincinnati Lead Study, a long-term lead exposure study conducted through the Cincinnati Children's Environmental Health Center, a collaborative research group funded by the National Institute of Environmental Health Sciences and U.S. Environmental Protection Agency. The Cincinnati Lead Study followed prenatal and early childhood lead exposure of 376 infants from high-risk areas of Cincinnati between 1979 and 1987. Over the course of the project, the children underwent behavioral testing and 23 blood analyses that yielded a mean blood lead level. Lead, a common and potent poison found in water, soil and lead-based paint, is especially toxic to children's rapidly developing nervous systems. Homes built before 1950 are most likely to contain lead-based paint, which can chip and be ingested by children. "Lead exposure has been associated with diminished IQ, poor academic performance, inability to focus and increased risk of criminal behavior," Cecil said.

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Chlorella vulgaris protects against lead-induced hepatic toxicity in rats

These results indicate that chlorella may have protective effect against lead-induced hepatic toxicity in rats.

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Scientists find way to remove lead from blood

South Korean scientists may have found a way to remove dangerous heavy metals such as lead from blood by using specially designed magnetic receptors.

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Zelfs lage blootstelling aan lood heeft invloed op IQ van kinderen

Children exposed to lead at levels now considered safe scored substantially lower on intelligence tests, according to researchers who suggest one in every 30 children in the United States suffers harmful effects from the metal. The study also found an average 5.5-point decline in IQ for every additional 10-microgram increase in blood-lead concentration, said Lanphear, a physician at Children’s Hospital Medical Center in Cincinnati.

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Some red lipsticks contain unhealthy levels of lead

Earlier this month, the watchdog group Campaign for Safe Cosmetics found that one-third of the lipsticks in a study of 33 red lipsticks contained levels of lead exceeding 0.1 parts per million.

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Exposure to lead, tobacco smoke raises risk of ADHD

Children exposed prenatally to tobacco smoke and during childhood to lead face a particularly high risk for ADHD, according to research done at Cincinnati Children's Hospital Medical Center. The study estimates that up to 35 percent of ADHD cases in children between the ages of 8 and 15 could be reduced by eliminating both of these environmental exposures. This could translate into up to 800,000 children. "Tobacco and lead exposure each have their own important adverse effect," says Tanya Froehlich, M.D., a physician in the Division of Developmental and Behavioral Pediatrics at Cincinnati Children's and the study's lead author. "But if children are exposed to both lead and prenatal tobacco, the combined effect is synergistic." The study is to be published online Nov. 23 by Pediatrics. "Although we tend to focus on ADHD treatment rather than prevention, our study suggests that reducing exposures to environmental toxicants might be an important way to lower rates of ADHD," says Robert Kahn, MD, MPH., a physician and researcher at Cincinnati Children's and the study's senior author.

The researchers found that children exposed prenatally to tobacco smoke were 2.4 times more likely to have ADHD. Those with blood lead levels in the top third had a 2.3 fold increased likelihood of ADHD, despite levels well below the Centers for Disease Control action level of 10 micrograms per deciliter. Dr. Froehlich and her colleagues found the risk of ADHD more than eight times higher for children exposed to both tobacco and lead compared to unexposed children. The study is based on data of 8 to 15 years olds gathered between 2001 and 2004 from the National Health and Nutrition Examination Survey (NHANES) from the National Center for Health Statistics at the Centers for Disease Control and Prevention. NHANES is a nationally representative sample of the United State population, designed to collect information about the health and diet of people in the U.S. Prenatal tobacco exposure was measured by maternal reports of cigarette use during pregnancy. Lead exposure was assessed using current blood lead level. Some 8.7 percent of the 3,907 children in the study met diagnostic criteria for ADHD. The diagnosis for ADHD was based on the Diagnostic and Statistical Manual for Mental Disorders, Fourth Edition, considered the "gold standard" for defining specific mental health conditions.


Children's blood lead levels linked to lower test scores

Exposure to lead in early childhood significantly contributes to lower performances on end-of-grade (EOG) reading tests among minority and low-income children, according to researchers at Duke University and North Carolina Central University. "We found a clear dose-response pattern between lead exposure and test performance, with the effects becoming more pronounced as you move from children at the high end to the low end of the test-score curve," said lead investigator Marie Lynn Miranda, director of the Children's Environmental Health Initiative (CEHI) at Duke's Nicholas School of the Environment. "Given the higher average lead exposure experienced by African-American children in the United States, our results show that lead does in fact explain part of the observed achievement gap that blacks, children of low socioeconomic status and other disadvantaged groups continue to exhibit in school performance in the U.S. education system, compared to middle- and upper-class whites," Miranda said. The study, published online in the peer-reviewed journal NeuroToxicology, linked data on blood-lead levels from the North Carolina Childhood Lead Poisoning Prevention Program surveillance registry to EOG reading test scores for 4th graders in all 100 of the state's counties. Researchers used innovative methods, including the use of a statistical approach called quantile regression, to measure the contribution of lead exposure to declining levels in children's EOG scores. Their analyses revealed that early childhood exposure to lead, the family's poverty status and parental education all account for test-score declines. On average, exposure to lead accounts for between 7 percent and 16 percent of the decline, with the larger declines associated with higher blood-lead levels. By comparison, they found the family's poverty status, as indicated by enrollment in a free or reduced-price school lunch program, accounts for 25 percent to 28 percent of EOG declines. And parental education accounts for the largest portion of the drop in test scores, between 58 percent and 65 percent of the total. "This demonstrates the particular vulnerabilities of socioeconomically and environmentally disadvantaged children," said Miranda, an associate professor at the Nicholas School and Duke Medical School's department of pediatrics. "Children who experience these cumulative deficits are especially disadvantaged when they enter the school system." The team's analysis showed that children already at the low end of the test-score curve were more greatly affected by lead exposure – the greater the exposure, the greater the impact on their scores. However, downward shifts were also documented in exposed children at the high end of the EOG curve. This is important, the study noted, because EOG scores are used to place students into advanced and intellectually gifted (AIG) programs at schools across the United States. "Our findings show that even low-level lead exposure can push some children out of the score range that would make them eligible for these special programs," Miranda said. "To the extent that low-income and minority children are systematically exposed to more lead, AIG programs become less economically and racially diverse."


Lead Poisoning in Kids


Lead in bone associated with increased risk of death from cardiovascular disease in men

Boston, MA -- Growing evidence shows that exposure to lead in the environment is associated with cardiovascular disease, including increased risk of hypertension. However, those studies have looked at lead concentrations in blood, not bone lead, a better indicator of cumulative lead exposure over time. In a new study, researchers at the Harvard School of Public Health (HSPH) and the University of Michigan School of Public Health found that bone lead was associated with a higher risk of death from all causes, particularly from cardiovascular disease. It is the first study to analyze the association between bone lead and mortality. The study appears online on September 8, 2009, on the website of the journal Circulation and will appear in a later print edition. "The findings with bone lead are dramatic. It is the first time we have had a biomarker of cumulative exposure to lead and the strong findings suggest that, even in an era when current exposures are low, past exposures to lead represent an important predictor of cardiovascular death, with important public health implications worldwide," said Marc Weisskopf, assistant professor of environmental and occupational epidemiology at HSPH and lead author of the study. Air pollution was the main source of lead in the environment in recent years, though it has been decreasing since leaded gasoline was banned in the U.S. in the mid-1990s. Most of the lead circulating in the body is deposited in bone and remains there for years, unlike blood lead, which has a half life of about 30 days. Since adverse effects from lead on the cardiovascular system would be expected to show up over time, the researchers expected that bone lead would be a better marker of chronic toxicity.

The researchers, led by Weisskopf and senior author Howard Hu, professor of environmental health, epidemiology and internal medicine at the University of Michigan School of Public Health, analyzed data from 868 participants in the Department of Veterans Affairs Normative Aging Study, a study of aging in men that began in 1963. Blood lead and bone lead—analyzed using X-ray fluorescence—were measured for each of the participants. The results showed that the risk of death from cardiovascular disease was almost six times higher in men with the highest levels of bone lead compared to men with the lowest levels. The risk of death from all causes was 2.5 times higher in men with the highest levels of lead compared to those with the lowest levels. The results appeared independent of age, smoking, education, race, alcohol, physical activity, BMI, high density lipoprotein or total cholesterol levels, hypertension or diabetes. There are a number of mechanisms, such as increased oxidative stress, by which lead exposure may result in cardiovascular mortality, say the authors. They also note that, in addition to high blood pressure, exposure to lead has been associated with widened pulse-pressure (an indicator of arterial stiffening) and heart disease. Given that bone lead may be a better biomarker of cumulative lead exposure than blood lead, it may be the best predictor of chronic disease from exposure to lead in the environment. "In addition to spurring further public health measures to reduce exposure to lead and to begin monitoring for cumulative exposure, mechanistic and clinical research is needed to determine if opportunities exist to conduct targeted screening and treatment that can further reduce the burden of cardiovascular disease for the millions of adults who have had years of elevated lead exposure in the past," said Hu.


Low lead levels in children can affect cardiovascular responses to stress

Even low levels of lead found in the blood during early childhood can adversely affect how the child's cardiovascular system responds to stress and could possibly lead to hypertension later in life, according to a study from the State University of New York (SUNY) at Oswego. Lead exposure was associated with an increase in vascular resistance when the children worked on a stressful computer task. Vascular resistance is a measure of tension within the blood vessels. Increased vascular resistance may lead to hypertension if it continues over time. The study also found that lead exposure was associated with a decrease in circulating aldosterone levels. Aldosterone is a hormone that helps regulate blood pressure. The study, Lead exposure and cardiovascular dysregulation in children, was conducted by James A. MacKenzie, Brooks B. Gump, Kristen Roosa, Kestas Bendinskas and Amy Dumas of the State University of New York, Oswego; Robert Morgan of Oswego Family Physicians; and Patrick Parsons of the New York State Department of Health. The researchers will present their findings, which during the 122nd annual meeting of The American Physiological Society (www.the-aps.org/press). The meeting is part of the Experimental Biology 2009 conference, to take place April 18-22 in New Orleans.

Ongoing research
In an earlier study with a different group of children, the researchers found that higher lead levels measured at 2 years of age were associated with an increased vascular response to stress later in life (average of 9.5 years of age). The present study aimed to determine whether this association was true when both lead and vascular responses were measured simultaneously, and if it did, how this happens. The researchers gave 140 children, 9-11 years old, a psychologically stressful computer task. They measured the children's cardiovascular function, including total peripheral resistance, while they were at rest and while they performed the stressful task. Total peripheral resistance is a measure of arterial pressure relative to cardiac output. The researchers compared the current blood lead levels of the children to their cardiovascular functioning during the experiment. As with the earlier study, they found that lead levels did correlate to the children's total peripheral resistance response to the stressful task. The finding is important because increases in total peripheral resistance may predispose people to hypertension later in life.

Low lead levels
One of the study's most important findings is that all of the participants had very low lead levels, well below the 10 micrograms per deciliter that the CDC defines as a level of concern. The highest lead level for the children in this study was 3.8 micrograms per deciliter. Children may be exposed to lead-based paint or lead-contaminated dust in their homes or pick it up from the soil outside. The Centers for Disease Control and Prevention (CDC) has pushed to minimize or eliminate all childhood exposure to lead. "The interesting thing was that the levels of lead were all pretty low in the children who participated," Dr. MacKenzie said. "We're seeing the negative effects at these low levels." While these are preliminary findings, the issue deserves more study, he said.

Search for the 'how'
In trying to find an explanation for how lead affects total peripheral resistance, the researchers found increased sympathetic nervous system activity during rest and, paradoxically, a depressed sympathetic response during the stressful computer task. Activation of the sympathetic nervous system produces the "fight or flight" response, raising the heart rate and constricting the blood vessels, among other things. Sympathetic nervous system activity is an appropriate response to stress, but can be harmful if activated for a long time.  "We believe lead causes an increase in sympathetic nervous activity during rest which reduces the body's ability to generate a response when stress comes along," Dr. MacKenzie said. In essence, the cardiovascular system is revving all the time, making it harder for the body to increase in sympathetic nervous system activity when needed. The study also found that serum aldosterone levels go down with higher lead levels, making it harder for the body to activate the sympathetic nervous system when needed. Dr. MacKenzie cautioned that the data on aldosterone and sympathetic activity is still preliminary and may be a focus of future research.


Lead in the blood increases women's mortality

Lead concentrations in the blood are associated with an increased risk of death from coronary heart diseases (CHD). A study of 533 American women, published in BioMed Central's open access journal Environmental Health, has shown that those with blood lead concentrations above 8?g/dL were three times more likely to die of CHD. Naila Khalil worked with a team of researchers from the University of Pittsburgh and the University of Maryland to study the effects of lead on the mortality of a group of 65-87 year old women who had joined an earlier study between 1986 and 1988. These women have been followed ever since and their causes of death recorded. Khalil said, "Despite population-wide declines in blood lead concentrations during the past 30 years, environmental lead exposure continues to be a public health concern. Lead is a toxic metal, and our results add to the existing evidence of adverse affects of lead on health as seen in an older cohort who experienced greater historic environmental lead exposure". The average population blood lead concentration in the most recent US National Health and Nutrition Examination Survey (2001-2002) had declined to 1.45?g/dL. The women studied in Dr. Khalil's research, however, were alive while lead was still used in paints, water systems and as a gasoline additive. They had an average blood concentration of 5.3?g/dL, with some women showing levels as high as 21?g/dL. According to Khalil, "Women with a blood lead concentration above 8?g/dL had a 73% increased risk of dying. In particular, blood lead was associated with almost three-fold risk in CHD mortality". This study shows that environmental toxicants, such as lead, may account for some of the burden of cardiovascular disease, which is the leading cause of mortality worldwide. It kills nearly half a million women in the United States every year, more than the next five causes of death combined and nearly twice as many as all forms of cancer, including breast cancer. The authors conclude, "While the damage may already have been done for some older people, it is important that we recognize the harm that environmental exposure to lead can cause. We must remain vigilant and ensure that lead pollution is minimized for the sake of future generations' health".


Calcium during pregnancy reduces harmful blood lead levels

Pregnant women who take high levels of daily calcium supplements show a marked reduction in lead levels in their blood, suggesting calcium could play a critical role in reducing fetal and infant exposure. A new study at the University of Michigan shows that women who take 1,200 milligrams of calcium daily have up to a 31 percent reduction in lead levels. Women who used lead-glazed ceramics and those with high bone lead levels showed the largest reductions; the average reduction was about 11 percent, said Howard Hu, chair of the Department of Environmental Health Sciences at the School of Public Health. Hu is the principal investigator of the study and one of the senior authors on the paper, which is available online in Environmental Health Perspectives, the official journal of the U.S. National Institute for Environmental Health Sciences. Hu, who is also affiliated with the University of Michigan School of Medicine, said this is the first known randomized study examining calcium supplementation on lead levels in pregnant women. "We and others have previously shown that during pregnancy, mothers can transfer lead from their bones to their unborn -- with significant adverse consequences--making maternal bone lead stores a threat even if current environmental lead exposures are low," Hu said. "This study demonstrates that dietary calcium supplementation during pregnancy may constitute a low-cost and low-risk approach for reducing this threat." Lead exposure is a great concern for pregnant and lactating women, especially in developing countries where lead exposures have been high until recently, and for women with occupational exposure. Developing fetuses and nursing babies are exposed to lead from either current exposures to mothers or from the mobilization of maternal skeletal lead stores accumulated from prior years of exposure. Bone lead can stay in the body for decades, so even with minimal environmental exposure, the fetus or nursing infant can still be at great risk from maternal stores of lead.

Lead exposure during fetal development and infancy can cause low birth weight or slow weight gain after birth, cognitive defects such as lower intelligence scores, lower motor and visual skills, or even miscarriage. Damage from lead exposure and poisoning is usually permanent.  "The bottom line is that obstetricians and pediatricians should consider adding calcium supplementation to the prenatal vitamins normally recommended in pregnant women, particularly if their patients have a significant history of environmental or occupational lead exposure," Hu said. The study showed that reductions in blood lead levels were more evident in the second trimester at 14 percent than in the third trimester at 8 percent. The most compliant group of women in the study (those who consumed greater than 75 percent of the assigned 1,200 milligram doses of calcium per day) showed a 24 percent decrease. Women in the most compliant group who also reported using lead glazed ceramics and had the highest bone lead levels saw the greatest reduction of 31 percent. Researchers analyzed 557 women recruited from the Mexican Social Security Institute prenatal clinics, which treat the low to moderate income population of Mexico City. All were in their first trimester; roughly half were assigned calcium and half a placebo. This recent study corresponds with a previous study performed by the same group of investigators showing that 1,200-milligram daily calcium supplementation during lactation reduced maternal blood lead by 15-20 percent, and breast milk lead by 5-10 percent. This is the first randomized trial to evaluate the effect of supplementation during pregnancy, when lead is more easily transferred to the fetus, Hu said.


Childhood lead exposure is associated with decreased brain volume in adults

Childhood exposure to lead is associated with shrinking (“volume loss”) of specific parts of the brain in adulthood, finds a related study in this week’s PLoS Medicine. Dr Kim Cecil and colleagues (University of Cincinnati, USA) studied the association between exposure to lead in the uterus and during early childhood and brain volume in adulthood. Childhood lead exposure has been linked to various types of brain damage, leading to problems such as abnormal thinking and behavior. But up until now, researchers have known little about how lead damages the brain in this way or about which brain regions get damaged by exposure to low to moderate levels of lead in childhood.

Dr Cecil and colleagues studied adults who were born in a poor area of Cincinnati during a time when it had a high concentration of older lead-contaminated housing. They recruited 157 such adults, aged between 15 and 17 years, who agreed to undergo specialized brain scans known as magnetic resonance imaging. The researchers found that exposure to lead as a child was linked with brain volume loss in adulthood, especially in men. There was a “dose-response” effect—in other words, the greatest brain volume loss was seen in participants with the greatest lead exposure in childhood. The specific regions of the brain involved were those responsible for organizing actions, decisions, and behaviors (known as “executive functions”), regulating behaviors, and coordinating fine movements (known as “fine motor control”).

“This analysis,” say the authors, “suggests that adverse cognitive and behavioral outcomes may be related to lead's effect on brain development producing persistent alterations in structure.” In an expert commentary on this study, Dr David Bellinger (Harvard Medical School, Boston, USA)—who was uninvolved in the research—says: “the associations observed by Cecil and colleagues provide a clear warning sign that early lead exposure disrupts brain development in ways that are likely to be permanent.”

Cecil KM, Brubaker CJ, Adler CM, Dietrich KN, Altaye M, et al. (2008) Decreased brain volume in adults with childhood lead exposure. PLoS Med 5(5): e112.


Children more vulnerable to harmful effects of lead

Contrary to prevailing assumptions, children are more vulnerable to the harmful effects of lead exposure at the age of 6 than they are in early childhood, according to a Cincinnati Children’s Hospital Medical Center study to be presented May 4 at the annual meeting of the Pediatric Academic Societies in Honolulu. “Although we typically worry about protecting toddlers from lead exposure, our study shows that parents and pediatricians should be just as, if not more concerned about lead exposure in school-aged children,” says Richard Hornung, Dr.P.H., a researcher in the division of general and community pediatrics at Cincinnati Children’s and the study’s main author. The researchers found that blood lead concentrations (BPb) at age 6, compared to those at younger ages, are more strongly associated with IQ and reduced volume of gray matter in the prefrontal cortex of the brain, which is involved in planning, complex thinking and moderating behavior. Overall, the children’s average BPb levels peaked at 13.9 micrograms of lead per deciliter of blood at age 2, then declined to an average of 7.3 micrograms per deciliter by age 6. For children, however, with the same average blood lead levels through age 6, those who received more of their exposure at age 6 had substantially greater decrements in intellectual ability than those more heavily exposed at age 2. “Lead toxicity is difficult to recognize in a clinical setting, but it can have devastating effects,” says Bruce Lanphear, M.D., director of the Cincinnati Children’s Environmental Health Center and the study’s senior author. “We found that children may be particularly vulnerable to lead exposure just as the child approaches school age, during a period of rapid cognitive development. Because IQ tests were not administered to children older than 6, it is unknown whether older children are even more vulnerable to environmental lead exposure, according to Dr. Hornung. Approximately 310,000 U.S. children age 1 to 5 years have blood lead levels greater than 10 micrograms per deciliter, the level at which the Centers for Disease Control and Prevention recommends public health actions be initiated. But research has consistently shown that blood lead levels considerably lower than 10 micrograms per deciliter are associated with adverse effects. Federal and state regulatory standards have helped to minimize or eliminate the amount of lead in U.S. consumer products and occupational settings, according to the National Institute of Environmental Health Sciences (NIEHS). Today, the most common sources of lead exposure in the United States are lead-based paint in older homes, contaminated soil, household dust, drinking water, lead crystal and lead-glazed pottery. While extreme lead exposure can cause a variety of neurological disorders, such as lack of muscular coordination, convulsions and coma, lower lead levels have been associated with measurable deficits in children’s mental development and behavioral problems. These include hyperactivity, or ADHD, lowered performance on intelligence tests, and deficits in fine motor function, hand-eye coordination and reaction time. Chronic lead exposure in adults can result in increased blood pressure, decreased fertility, cataracts, nerve disorders, muscle and joint pain as well as problems with memory or concentration.


Expert at UH adds obesity to side effects of lead exposure

Optometry professor finds unexpected link between prenatal lead exposure and obesity in males. Scientists know exposure to low levels of lead can result in learning disabilities, hearing loss, language impairments and vision loss, but a newly discovered side effect may be adult-onset obesity in men, according to a University of Houston professor. Ronald Fox, a UH professor of vision sciences, biology and biochemistry, and pharmacology, uncovered the link between lead exposure and obesity while studying the effects of lead on the retina in mice. Fox found this more subtle side effect was due to exposure to lead while in the womb, unlike the rash of reports of children becoming sick from ingesting lead-based toys.To reach his conclusions, Fox and collaborator Leigh Leasure, an assistant professor of psychology with UH, undertook an 18-month case study exposing pregnant mice to varying levels of lead in their drinking water to observe the effects on the offspring. By adding obesity to the already lengthy list of lead exposure side effects, Fox hopes the Center for Disease Control and Prevention (CDC) will lower the acceptable lead exposure rate for pregnant women and children. “The CDC states that the acceptable low-level exposure amount is equal or less than 10 micrograms per deciliter of blood for mothers or children,” Fox said. “The acceptable level used to be at 80 micrograms in 1972, but in the 1980s, it dropped to 60. There’s a push among scientists to drop it down to five, three or two micrograms per deciliter. “For our experiment, we exposed the pregnant mice and, by extension, their babies to varying levels of lead through their drinking water,” Fox said. What happened with the mice surprised Fox and his team. Initially, the prenatally exposed mice were developing at the same rate as their control counterparts, but at one year, some startling changes began to occur. “These animals were slower, less coordinated and fatter at a year old,” Fox said. “Mice exposed to 10 micrograms – the CDC standard for acceptable exposure – gained about 25 percent more weight than their control counterparts.” A 1-year-old male mouse is the equivalent of a 30- to 40-year-old man, he said. But what surprised Fox and his team even more was that the obesity side effect was strictly limited to the male mice. “We don’t know if the weight gain was related to testosterone or other hormones, but we’re trying to figure out why females weren’t affected,” Fox said. Humans can encounter lead exposure through the soil, dust, air, water, paint and toys, and because lead accumulates in the body, even minimal lead exposure can have long-lasting effects, according to Fox. Fox’s results will be published in Environmental Health Perspectives in March, but he will continue studying the effects of lead in mothers and their offspring.


Lead-Poisoned Kids May Still Be Unsafe After Relocating

In Chinas Shaanxi province—where hundreds of children were sickened by lead poisoning from a local factory—families may still be at risk. According to state media, more than 80 percent of kids in two villages nearby the smelting plant have dangerously high levels of lead in their blood.


Jefferson neuroscientists find early lead exposure impedes recovery from brain injury

Exposure to lead can hinder the brain’s ability to recover from injury, a recent study in laboratory animals shows. The results have implications for the effects of environmental lead exposure on brain injuries such as stroke, say researchers at Jefferson Medical College, who led the work. Lead exposure early in life is known to increase the risk for cancer, renal disease, hypertension and cardiovascular disease later in life, and as a result, also increases the risk for stroke and brain damage. Jay Schneider, Ph.D., professor of Pathology, Anatomy and Cell Biology and Neurology at Jefferson Medical College of Thomas Jefferson University in Philadelphia and postdoctoral fellow Emmanuel Decamp, Ph.D., wanted to know if it was possible that lead might alter the potential for plasticity, the ability of the brain to compensate for an injury. They studied young rats that were fed a diet supplemented with lead and compared them to others on a diet without lead. In earlier work in the lab, they found that even brief exposures to lead affected neurotrophic factors in the brain important for growth and maintenance of neurons and their connections. They ran each group through some simple behavioral tests before causing a small stroke in a specific part of the brain that affected a hind limb. Reporting in the journal NeuroToxicology, Dr. Schneider, who is director of the Parkinson’s Disease Research Unit at Thomas Jefferson University, and his group saw significant recovery after a brief period of time in the control group, “as compensatory processes take over,” though the limb function was not completely back to normal.

“In contrast, those animals that were exposed to lead earlier in life had worse outcomes in the same period after the stroke,” he says. “There was significant difference in the brain’s ability to compensate for that injury.” Because the study was brief, he says, they don’t know if in a longer period of time the lead-exposed animals would catch up in their recovery to the controls. There was some recovery in the lead group, but then it leveled off. The control group continued to get better. “That’s one of the questions we would like to pursue in further studies – whether lead exposure slows or attenuates the recovery process after a brain injury,” Dr. Schneider notes. “Have they recovered as much as they will recover or given more time, would they recover to the same extent" Is lead exposure affecting the rate of recovery or the recovery potential"” According to Dr. Schneider, it is well known that lead exposure had detrimental effects on learning and memory, other forms of brain plasticity. “Brain plasticity generally refers to the brain’s ability to be molded by experience as well as its ability to reorganize anatomically and functionally and recover from injury,” Dr. Schneider says. “It’s why people who have relatively small strokes can recover function. The brain has an innate ability to reorganize and repair itself. Our data suggest that lead exposure may compromise or alter this capacity for remodeling that may impair recovery of function following brain injury.” Next, the group would also like to see if such a trend translates to recovery from other types of injury, such as traumatic brain injury. They would also like to explore the notion that childhood lead exposure increases the risk of a child having a poorer outcome from an acquired brain injury. Dr. Schneider explains that one important aspect of lead poisoning is impairment of plasticity. “The data we have begin to support that,” he says. “We want to look at the effects of different levels of lead exposure on the outcome from acquired brain injury and see how different types and extents of exposures correspond with the expression of injury and recovery of function. Then, we want to try to nail down the biological processes responsible.”


Even minute levels of lead cause brain damage in children

Even very small amounts of lead in children's blood -- amounts well below the current federal standard -- are associated with reduced IQ scores, finds a new six-year Cornell study. The study examined the effect of lead exposure on cognitive function in children whose blood-lead levels (BLLs) were below the Centers for Disease Control and Prevention (CDC) standard of 10 micrograms per deciliter (mcg/dl) -- about 100 parts per billion. The researchers compared children whose BLLs were between 0 and 5 mcg/dl with children in the 5-10 mcg/dl range. "Even after taking into consideration family and environmental factors known to affect a child's cognitive performance, blood lead played a significant role in predicting nonverbal IQ scores," says Richard Canfield, a senior researcher in Cornell's Division of Nutritional Sciences and senior author of the study in the journal Environmental Health Perspectives. "We found that the average IQ scores of children with BLLs of only 5 to 10 mcg/dl were about 5 points lower than the IQ scores of children with BLLs less than 5 mcg/dl. This indicates an adverse effect on children who have a BLL substantially below the CDC standard, suggesting the need for more stringent regulations," he said. In the United States over the last several months, nearly 50 specific products, including millions of toys for young children, have been recalled due to excessive lead in the paint, plastics and metal. "Our findings emphasize the very real dangers associated with low-level exposures, to which lead in toys can contribute," Canfield said.

U.S. children are exposed to lead primarily from household dust contaminated by deteriorating interior lead-based paint. In addition to toys, other potential sources include contaminated soil, imported food stored in lead-glazed pottery and certain plastic, metallic and painted products. This most recent finding builds on the same research team's influential 2003 study, published in the New England Journal of Medicine, that reported adverse effects of BLLs below 10 mcg/dl in a group of children followed from infancy to age 5. "Our new findings are based on follow-up testing of the same children at age 6, using a more comprehensive IQ test to assess cognitive function. The results provide compelling evidence that low-level lead exposure has effects into the school-age years," said Todd Jusko '01, a University of Washington Ph.D. candidate in epidemiology and co-author on both reports.

"Children living in poverty disproportionately suffer from elevated BLLs," said statistician and co-author Charles Henderson, a Cornell senior researcher in human development. He also noted that "even a small decline in an IQ score is likely to be reflected in aptitude test scores such as the SAT." According to the CDC, about one out of every 50 children in the United States between ages 1 and 5 has a BLL above 10 mcg/dl and about 10 percent of children have BLLs of 5 mcg/dl or higher; about 25 percent of U.S. homes with children under age 6 have a lead-based paint hazard. "The bottom line," according to Canfield, "is that lead is a persistent neurotoxin that causes brain damage. The fact that lead has been found in millions of toys, even toys specifically designed for children to put into their mouths, presents an unacceptable risk. Our findings suggest the need to re-evaluate the current federal standards for lead in consumer products and the current definition of an elevated BLL in children."


Safe' blood lead levels linked to risk of death

Blood lead levels generally considered safe may be associated with an increased risk of death from many causes, including cardiovascular disease and stroke, according to a report in Circulation: Journal of the American Heart Association. Researchers studied lead levels below 10 micrograms per deciliter (g/dL) which previously has been considered safe. The levels studied are common and considerably lower than lead levels perceived by the government as a concern to public health, said Paul Muntner, Ph.D., author of the study and an associate professor of epidemiology and medicine at Tulane University School of Public Health and Tropical Medicine in New Orleans. "Our study found the association of blood lead with cardiovascular death to be evident at levels as low as 2 g/dL," he said. "Since 38 percent of U.S. adults had lead levels above 2 g/dL in 1999–2002, the public health implications of these findings are substantial." The Occupational Safety and Health Administration (OSHA) defines high blood lead in adults as higher than 40 g/dL. The Centers for Disease Control and Prevention recommend that women of child-bearing age have blood lead levels below 10 g/dL. Researchers said the study questions the current belief about what lead levels are safe in the population. "We wanted to know whether there was an association between the current blood lead levels among U.S. adults and coronary heart disease, stroke or cancer," Muntner said. Since the mid-1970s, when lead was no longer added to gasoline or household paint and lead was banned for use in soldering food cans, average blood lead levels in American adults have decreased from 13.1 g/dL to 1.6 g/dL. "Even though lead levels are much lower than before, the current levels are still orders of magnitude higher than pre-industrial levels," Muntner said. Today lead is mostly used to make batteries. It is also used to make ammunition (bullets), pipes and roofing materials. According to OSHA, exposure to lead can occur in at least 120 occupations including lead smelting, battery manufacturing, ship building/repair, auto manufacturing and printing. Breathing contaminated air, eating contaminated food or soil, or drinking contaminated water are ways people can be exposed to lead. Inhalation of airborne lead is generally the most significant source of occupational lead absorption. The researchers used data from the Third National Health and Nutrition Examination Survey Mortality Follow-Up Study, involving 13,946 adults whose blood lead levels were collected and measured between 1988 and 1994. When researchers studied those who died by Dec. 31, 2000, they found that death from any cause, cardiovascular disease, heart attack and stroke increased progressively at higher lead levels. Compared to participants with blood lead below 1.9 g/dL, participants with blood lead between 3.6 g/dL and 10 g/dL had:

* a 25 percent higher risk of death from any cause
* a 55 percent higher risk of death from cardiovascular diseases
* an 89 percent higher risk of death from heart attack
* two and a half times the risk of death from stroke

"The increased risk of all-cause and cardiovascular deaths with increased lead levels affected all groups we studied: non-Hispanic whites, non-Hispanic blacks and Mexican Americans, as well as males and females," Muntner said. "The risk of death from cancer did not increase at the blood lead levels that our study investigated. "Our study had limited ability to evaluate the risks of lead exposure associated with blood lead levels below 2 g/dL. Future research is needed to identify the level of lead exposure that is not associated with major health outcomes. Although markedly reduced, the current blood lead levels may not be low enough, and we believe that practical and cost-effective methods for reducing lead exposure in the general U.S. population are needed."


Long-term lead exposure linked to cognitive decline in older adults

Older adults exposed to high levels of lead before the 1980s are showing signs of cognitive decrements as a result of long-term lead exposure in their communities, according to a study published in the online edition of Neurology, the scientific journal of the American Academy of Neurology. The study involved 985 adults randomly selected throughout the city of Baltimore, Maryland. The participants were between the ages of 50 and 70 years old and had been exposed to higher levels of lead prior to the 1980s when lead had been used extensively in commercial products. In determining the association between high levels of lead and lower cognitive performance, researchers tested the amount of lead in the tibia, or shinbone, since lead accumulates in bone. Participants also performed 20 cognitive tests to measure language, processing speed, eye-hand coordination, executive functioning, verbal memory and learning, and visual memory. The study found higher tibia lead levels were consistently associated with worse cognitive performance on tests. "The analysis showed the effect of community lead exposure was equivalent to two to six years of aging," said principal investigator Brian Schwartz, MD, with Johns Hopkins Bloomberg School of Public Health in Baltimore. "If lead is associated with lower cognitive performance, this may suggest possible treatment and prevention options for older adults." In addition, the study found tibia lead levels were significantly higher in African Americans compared to Caucasians. Researchers say the difference likely represents the long-term higher environmental lead exposures sustained by African Americans in the United States, but could also be due to different bone mineral densities in African Americans compared to Caucasians.


Study links lead exposure to brain cancer in adults

People who are routinely exposed to lead on the job are 50 percent more likely to die from brain cancer than people who are not exposed, according to a University of Rochester Medical Center study. More than 18,000 brain and spinal cord tumors will be diagnosed in the United States this year. Yet little is known about what causes brain cancer; the only established risk factor is radiation, according to the American Cancer Society. Results of other studies attempting to show a clear link between lead and cancer have been inconclusive. The new data, based on information from the U.S. Census Bureau and the National Death Index, may be the largest study ever to find a lead-cancer link. In doing so it provides further evidence that widespread environmental risk factors such as lead must be explored, said study author Edwin van Wijngaarden, Ph.D. "If we are able to help explain the cause of even 1 or 2 percent of the total number of cases, that's important," said van Wijngaarden, an assistant professor and epidemiologist in the Department of Community and Preventive Medicine at the University of Rochester. Published in the Sept. 1, 2006, issue of the International Journal of Cancer, the study computed the risk estimates for lead exposure and brain cancer from a census sample of 317,968 people who reported their occupations between 1979 and 1981. Van Wijngaarden was looking for evidence of an exposure-response trend, or a rise in cancer incidence or mortality associated with an exposure to a toxic substance. The goal among researchers who do this type of investigation is to identify preventable, environmental risk factors that might cause the gene mutations that lead to cancer.

Each occupation was classified into categories established by the National Cancer Institute. The NCI job matrix for lead is designed to estimate the likelihood of exposure and the intensity of exposure. It rates each occupation on a scale from zero (no exposure) to three (high exposure). Gas station attendants from the 1970s and early 1980s, for example, were estimated to have a high probability of exposure, but only medium intensity of exposure because their direct contact with leaded gasoline was not as great as the potential for contact. The jobs with the highest probability and intensity of lead exposure were painters and automobile mechanics. But firefighters, engineers, automobile assemblers, truck drivers, plumbers, welders, and printers or typesetters were all among those individuals with some likelihood of lead exposure, according to the NCI matrix. When Van Wijngaarden applied the matrix to nearly 318,000 people and followed their cancer rates for nine years, he found 119 brain cancer deaths. The death rate among people with jobs that potentially exposed them to lead was 50 percent higher than unexposed people, and the number of deaths was larger than in many previous studies, van Wijngaarden said. Other trends that emerged were slightly higher death rates among less educated and married individuals. Scientists have suspected for years that lead is a carcinogen, which passes through the blood-brain barrier, making the brain especially sensitive to the toxic effects of lead. Van Wijngaarden is continuing his research with a pilot study to measure the actual bone-lead levels in people who have been diagnosed with brain tumors. "My interest is in exploring the long-term implications of lead exposure," van Wijngaarden said. "Lately, a lot of the information about lead and its toxicity has focused on children. We do know that in young people it can cause acute illness and behavioral problems. But what is under appreciated, I believe, are the chronic health effects."


Growing body of research links lead to osteoporosis

Bolstered by recent laboratory findings, researchers at the University of Rochester Medical Center are embarking on a National Institutes of Health-funded clinical study to better understand the deceptive role environmental lead exposure plays in bone maturation and loss. The clinical trial is the latest in a growing body of research that is putting yet one more notch in the belt of diseases attributed to lead, and this time, researchers say, its target is older adults at risk for osteoporosis. For decades, scientists have known that the human skeleton is a repository for lead in people who were exposed to high levels of this environmental toxin in their childhood, but thought this storage to be benign. Recently, a growing body of research is showing that the opposite is true, and that lead in bone actually sets off a bizarre chain reaction, first accelerating bone growth, and then eventually limiting it so that a high peak bone mass is not achieved. Preventing a high peak bone mass will predispose a young person to osteoporosis later in life. Now, researchers in the Center for Musculoskeletal Research at the University of Rochester Medical Center are set to embark on the next phase of a four-year, $5 million research project funded by the National Institute of Environmental Health Sciences with a clinical study aimed at better understanding the deceptive role lead initially plays in bone development, growth and loss – and how this all might lead to earlier onset of osteoporosis in those exposed to high levels of lead as a child. A metabolic bone disease that predominantly occurs in women, osteoporosis affects one in three American women over the age of 65. It is characterized by low bone mass that eventually leads to fractures, mostly of the hip and vertebrae. These fractures can be life-threatening; experts say that more women die each year from hip fracture complications than from cancer of the ovaries, cervix and uterus combined. Close to $20 billion dollars is spent each year treating osteoporosis and related fractures.

An Ironic Growth Pattern

The pattern of growth in the skeleton determines the peak skeletal density of an individual, and this level is established by the time most people reach 20. Recent research completed at the University of Rochester Medical Center shows that lead adversely affects the normal maturation of the growth plate – but does so in an odd way. "As a child, lead appears to accelerate bone development and maturation, so that lead-exposed children actually have a higher bone density than those not exposed to environmental lead," said James Campbell, M.D., M.P.H., associate professor of Pediatrics and a co-investigator of the study. "But, we believe this higher bone density effect is short-lived, and in fact, we believe it actually prevents these children from achieving an optimal peak bone mass later on in life." J. Edward Puzas, Ph.D., professor of Orthopaedics and director of the overall project, added that limiting peak bone mass has dire consequences as a person begins to age.  "When everyone begins to lose bone mass starting at around age 50, lead-exposed individuals are at a higher risk for bone fractures and osteoporosis – and probably at an earlier age than the typical osteoporosis patient." At what specific age lead-exposed individuals will plateau in bone growth, and at what age they will begin to lose more bone as older adults, is the focus of this clinical research. Puzas and Campbell have used their prior research to guesstimate when these two milestones occur, but are turning to sophisticated lead measurement devices to help them pinpoint exact timeframes. "We believe that somewhere around age 20, we'll begin to see low-lead exposed individuals surpass high-lead exposed individuals in bone mass density," Campbell said. "Then, in the 50 to 60 age group – the age at which any individuals will begin to experience a natural loss of bone – we expect to see the high-lead exposed individuals losing more bone sooner."


Your tap water: Will that be leaded or unleaded?

Lead may pose greater leaching risk than standard tests show
In critiquing a common safety standard for brass used in plumbing, researchers have found the regimen may be flawed. As a result, they say, some of the lead that crept into tap water in Washington, D.C., and other metropolitan areas may be traceable to household fixtures, valves and other components and not just pipes and systems further from the home. The new study looked at the American National Standards Institute/National Sanitation Foundation 61 Section 8 standard--a protocol consisting of specific methods and test-water formulas that governments and industries have relied upon to ensure safe plumbing since 1988.

"As a result of problems identified with the test protocol, some products passing National Sanitation Foundation Section 8 may have a greater capacity to leach lead into water than we believed," said Marc Edwards of Virginia Tech, who is one of the study leaders. Edwards, Abhijeet Dudi and Nestor Murray, all at Virginia Tech, and Michael Schock, of the Environmental Protection Agency (EPA) National Risk Management Research Laboratory, report their findings in the Aug. 4 issue of the Journal of the American Waterworks Association. Edwards, Dudi and Murray are members of a multidisciplinary team supported by a National Science Foundation Materials Use: Science, Engineering and Society (MUSES) award. The researchers tested identical brass devices purchased from a local hardware store by subjecting the pieces to the Section 8 protocol and to modifications they made to the protocol. They also applied the same tests to a simulated plumbing device made of solid lead. The results: The Section 8 water samples reacted less, or were less "aggressive," with lead in the plumbing than designers of the standard had intended. The researchers found other problems that stemmed from calculations that underlie some of the test results. Normalization factors allow evaluators to estimate actual lead concentrations at the tap, but they are affected by device size. Because of normalization and the non-aggressive waters, the small, simulated device made of pure lead pipe passed the Section 8 leaching test. The scientists began to scrutinize the Section 8 methods after learning that one of the test solutions contains high concentrations of orthophosphate to buffer the water's pH. Water utilities use orthophosphate actually to inhibit lead leaching. So, test solutions containing such leaching inhibitors could not react adequately with plumbing and would produce a flawed reading.

"It's analogous to an automobile crash test using a wall of pillows," Edwards said. Because lead softens alloys, it is an important component in many plumbing metals. Without adding small quantities of lead, manufacturers could not craft intricate shapes necessary for modern devices. Under certain chemical conditions, such as high acidity or low amounts of carbon dissolved from minerals, the devices can leach significant amounts of that lead into water. The problem is complex because treatments necessary to treat one water-quality problem, such as bacteria, can have unintended consequences, such as lead leaching. In the 1986 Safe Drinking Water Act as amended in 1996 (USEPA, 2000), Congress explicitly banned new devices containing pure lead pipe, leaded solders, and brass with more than 8 percent lead content. However, these materials remain installed in older homes. At the time of the legislation, there were no alternatives for leaded brass, and experts believed it was not feasible to reduce lead content in devices to that in pipes and solder. Some components are labeled lead-free, even if they contain 7.99 percent lead. Despite such labeling, all brass products that contain lead must pass the Section 8 performance-testing standard. Recently, legislators have proposed updated laws to allow for modern brass alloys--some containing as little as 0.02 percent lead or less by weight--which could reduce lead leaching considerably .


New study links lead exposure with increased risk of cataract

Results from a new study show that lifetime lead exposure may increase the risk of developing cataracts. Researchers found that men with high levels of lead in the tibia, the larger of the two leg bones below the knee, had a 2.5-fold increased risk for cataract, the leading cause of blindness and visual impairment. "These results suggest that reducing exposure of the public to lead and lead compounds could lead to a significant decrease in the overall incidence of cataract," said Kenneth Olden, Ph.D., director of the National Institute of Environmental Health Sciences. The National Institute of Environmental Health Sciences, one of the National Institutes of Health, provided support to researchers at the Harvard School of Public Health and Brigham and Women's Hospital for the nine-year study, which is also focusing on lead's contribution to hypertension and impairment of kidney and cognitive function. The findings on risk of cataract are published in the December 8th issue of the Journal of the American Medical Association. Lead is found in lead-based paint, contaminated soil, household dust, drinking water, lead crystal, and lead-glazed pottery. Following exposure to lead, the compound circulates in the bloodstream and eventually concentrates in the bone. The Harvard researchers tested whether bone lead levels measured in both the tibia and patella, also known as the kneecap, were associated with cataract in an ongoing study of men taken from the Boston area. "Given the strong association between tibia lead and cataract in men, we estimate that lead exposure plays a significant role in approximately 42 percent of all cataracts in this population," said Debra Schaumberg, Sc.D., assistant professor of medicine and ophthalmology at Harvard Medical School and lead author of the study. "While lead in both the tibia and patella was associated with an increased risk of cataract, tibia lead was the best predictor of cataract in the study sample."

According to Schaumberg, cataracts develop as a result of cumulative injury to the crystalline lens of the eye. "Lead can enter the lens, resulting in gradual injury to certain proteins present in the epithelial cells, and this eventually results in a cataract," she said. The Harvard researchers are among the first to use bone lead in studying the effect of lifetime lead exposure on disease risk. "The best biological marker for estimating a person's cumulative exposure to lead is provided by skeletal lead," said Dr. Howard Hu, professor of occupational and environmental medicine at the Harvard School of Public Health and co-author of the study. "Since blood lead levels reflect only recent exposures, they are not likely to predict the development of age-related diseases such as cataract, which take many years to develop." Cataracts, a clouding of the lens resulting in a partial loss of vision, are very common in older people. By age 80, more than half of all Americans either have a cataract or have had cataract surgery. Other risk factors for cataract include diabetes, smoking, long-term alcohol consumption, and prolonged exposure to ultraviolet sunlight. The prevention of age-related cataract remains an important public health goal," said Schaumberg. "In addition to the obvious problems of reduced vision, the visual disability associated with cataracts can have a significant impact on the risk of falls, fractures, quality of life, and possibly even mortality."


'Safe' lead levels pose risk to children's cognitive functioning

ITHACA, N.Y. -- A five-year study has found that lead is harmful to children at concentrations in the blood that are typically considered safe.

Reporting in the latest issue (April 17) of The New England Journal of Medicine , two Cornell University scientists say that children suffer intellectual impairment at a blood-lead concentration below the level of 10 micrograms per deciliter (mcg/dl) -- about 100 parts per billion -- currently considered acceptable by the Centers for Disease Control and Prevention (CDC). "We also found that the amount of impairment attributed to lead was most pronounced at lower levels," says Richard Canfield, lead author of the journal paper and a senior researcher in Cornell's Division of Nutritional Sciences.

The study followed 172 children in the Rochester, N.Y., area whose blood lead was assessed at 6, 12, 18, 24, 36, 48 and 60 months and who were tested for IQ at both 3 and 5 years of age. The study was conducted by researchers at Cornell, the Cincinnati Children's Hospital, the University of Rochester, the National Institutes of Health and the University of Washington.

Before 1970, childhood lead poisoning was defined by a blood-lead concentration greater than 60 mcg/dl. The level considered acceptable was set at 40 mcg/dl in 1970 and reduced to 25 mcg/dl in 1985. The current level of 10 mcg/dl was established in 1991 based on findings linking lead at this level to lowered intelligence and diminished school performance.

An important feature of the study is its focus on children with blood-lead levels below 10 mcg/dl. Most previous research examined the effects of lead in the 10 to 30 mcg/dl range. But the new study finds lead-related impairments at lower levels.

"In our sample, most of the damage to intellectual functioning occurs at blood-lead concentrations that are below 10 mcg/dl," says Canfield. The amount of impairment was also much greater than the researchers had expected. "Given the relatively low exposure levels, we were surprised to find that the IQ scores of children with blood-lead levels of 10 mcg/dl were about 7 points lower than for children with lead levels of 1 mcg/dl," Canfield says.At the same time, the study found that an increase in blood lead from 10 to 30 mcg/dl is associated with only a small additional decline in IQ of about 2 to 3 points. "Because most prior research focused on children with higher exposures than in our sample, we suspect those investigators could estimate only the damage that occurs after blood lead has reached 10 mcg/dl -- unaware that substantial impairment may occur at lower levels," says Charles Henderson, a senior researcher in the Department of Human Development at Cornell and se! cond author of the paper.

"While these findings are based on a single sample and will need to be replicated in further studies," says Henderson, "we found that the relation between lead and IQ was very consistent at 3 and 5 years of age." He notes that the researchers controlled for maternal education, IQ, income, prenatal exposure to tobacco and level of intellectual stimulation in the home.

Children's blood-lead concentrations have fallen by more than 80 percent in the past 30 years, but Canfield notes that undue lead exposure is an especially important problem among children living in impoverished communities. For example, the CDC recently reported that children ages 1 to 5 years who were enrolled in Medicaid accounted for 60 percent of all U.S. children with blood-lead levels greater than 10 mcg/dl. Furthermore, more than 80 percent of children enrolled in Medicaid do not typically receive blood-lead tests. Many such children live in housing built before about 1950, which is more likely to contain paint having high levels of lead. If the paint cracks or peels, lead particles can fall onto floors and onto children's toys. Children ingest the lead particles when they put contaminated toys and fingers into their mouths.

According to new CDC figures, approximately 1 out of every 50 children in the United States between the ages of 1 and 5 years has a blood-lead level above 10 mcg/dl, whereas 1 in every 10 children has blood-lead levels of 5 mcg/dl or higher. "Given the current CDC recommendations and the findings from our study, it appears that many children are passing their lead test but failing to escape the adverse consequences of low-level lead exposure," Canfield says.


Study shows how eye cells die when exposed to lead

UH research suggests possible therapies for eye disorders, injury

A new study designed to find out why cells in the eye die when exposed to lead may provide novel therapies for retinal damage caused by injury or diseases such as diabetes and retinitis pigmentosa.

The study, published in the Feb. 4 issue of the Proceedings of the National Academy of Sciences, focused on identifying how low-level lead exposure during development in mice injures and eventually kills rod-shaped photoreceptor cells, or rods, in the eye.

Rods are cells in the eye that help humans see in dim light. The other type of photoreceptors, or light-gathering cells, called cones are responsible for color and spatial vision. Cones are used primarily in daylight and for activities such as reading.

"Lead is a toxicant, and when the retina is exposed to lead, we found that it triggers a chain of biochemical events that leads to the selective apoptotic death of rod photoreceptors," says Donald A. Fox, professor of vision sciences, biology and biochemistry, and pharmacology at the University of Houston and principal investigator of the study.

"The human eye contains so many rods that you can lose about 20 percent of them and not have much functional loss of vision," Fox says. "But for people who need to see clearly at night, such as truck drivers, or for people who are losing their rods due to disease or injury, finding a way to prevent the rods from dying is important."

In June 2002, Fox and his colleagues published a study showing that 7- to 10-year-old children whose mothers had elevated levels of lead in their blood during the first trimester of pregnancy developed retinal abnormalities, specifically in their rods (Investigative Ophthalmology & Visual Science, June 2002, Vol. 43. No. 6). A study currently underway with the same children is assessing whether lead exposure during development affects the eye's cones as well.

"We can't tell whether the rods actually die, because these are living children, but there are unique functional abnormalities in these children. They may have visual system deficits that eventually could lead to permanent retinal alterations and learning problems," Fox says. "We're not sure what the functional basis of this observation is, and we hope to study it further."

According to the Centers for Disease Control and Prevention, the acceptable level of lead in the blood is 10 micrograms per deciliter. The CDC estimates that about 900,000 U.S. children under age 6 have blood lead levels at that level or higher. The children in Fox's ongoing study live in and around Mexico City and had blood lead levels of 6 micrograms per deciliter or above.

Fox's latest animal study in PNAS sheds some light on the mechanisms responsible for lead-mediated cell death, or apoptosis, in the eye, and may suggest possible treatment options for patients suffering from various forms of retinal degeneration.

The key to most cell death is a structure within each cell called the mitochondrion, which is known primarily as the central component responsible for generating energy for the cell. But when a cell is damaged, the mitochondria become the "central executioners," releasing proteins sequestered within them that are death signals for the cell.

Here's how Fox believes lead-mediated cell death occurs:

When the rod cells in the eye are exposed to lead, it triggers an increase in the amount of lead and calcium entering the cell. A higher level of calcium within the mitochondria sensitizes the mitochondria to interact with a "death factor" protein produced by the cell called Bax. Fox says Bax seems to cause channels, or pores, in the mitochondria to open up and release yet another "death factor" protein called cytochrome c. This protein eventually causes changes that wreak havoc on the cell's nucleus, destroying its DNA and killing the cell.

"The mitochondrion is like a fort that's tightly guarded," Fox explains. "Normally things don't get out. But Bax appears to open up the gate to the fort, letting cytochrome c escape."

Guy Perkins, Fox's colleague at the National Center for Microscopy and Imaging Research at the University of California, San Diego, produced detailed images of the animals' rod mitochondria for the study.

"We found the lead-exposed eyes had more of these 'gates,' which are called contact sites, opened up along the surface of the mitochondria than the non-exposed eyes, and we believe these contact sites are associated with the cytochrome c release," Fox says.

The researchers also found that an excess of an anti-death protein called Bcl-xL completely blocked the death of the eye's rod cells and maintained normal mitochondrial function in the rods throughout adulthood.

"All cells produce anti-death proteins like Bcl-xL, and normally when they combine with Bax, it prevents Bax from triggering cell death. Too much Bax results in cell death," Fox says.

"But these transgenic mice were genetically engineered to produce excessive amounts of Bcl-xL in their rod cells. We found that these overexpressed levels of Bcl-xL blocked the Bax from associating with the mitochondria, as well as blocked the increased formation of contact sites and release of cytochrome c from the mitochondria. If the cytochrome c can't get out of the mitochondria, the cells do not die."

The research results suggest possible avenues for treatment of some eye disorders.

"For people whose rods are dying, such as in retinitis pigmentosa, or diabetes, or immediately after a traumatic eye injury, if you can get higher levels of this anti-death protein, Bcl-xL, or one like it, into the eye, it could help prevent cell death. It has relevance for therapies for a wide variety of retinal degenerations," Fox says.

The key to Fox's experiment was to expose the mice to lead levels that are relevant to environmental levels of lead that humans might be exposed to. "Previous animal models have used lead levels that were not consistent with the low-level lead exposure and slow cellular degeneration that actually occurs in human disease," he says.


US researchers find first conclusive evidence that lead is linked to male infertility

A report in Europe's leading reproductive medicine journal Human Reproduction[1] concludes that exposure to lead damages sperm function and may be a contributory cause of unexplained male infertility.[2]

The findings have led principal investigator Dr Susan Benoff to urge doctors to measure lead in seminal plasma when evaluating men from couples with unexplained fertility. She also believes there is a case for health and safety authorities to continue re-evaluating environmental exposure limits.[3]

Dr Benoff, director of the Fertility Research Laboratories at the North Shore-Long Island Jewish Research Institute in Manhasset, New York, and colleagues from several other US institutions, undertook a prospective, double-blind study of metal ion levels and sperm function in semen from the partners of 140 consecutive women undergoing their first IVF cycle.

They found that lead levels in seminal plasma varied over a wide range and there was a significant association between high lead levels and a low fertilisation rates, with changes in lead levels accounting for a fifth of the variance in fertilisation rates.

"From our tests on lead in the seminal plasma of the participants and control experiments on nine fertile donors, we have evidence that higher lead levels interfere both with the ability of the sperm to bind to the egg and with its ability to fertilise the egg," said Dr Benoff.

In order to fertilise an egg, a sperm has first to bind to it. A sugar called mannose on the outer coating of the egg is crucial to binding. Mannose receptors located on the head of human sperm recognise the mannose on the coating of the egg and regulate the binding process.

Then the sperm has to penetrate the egg. Successful binding induces an event called mannose-induced acrosome reaction – the release of digestive enzymes from the sperm that ease its passage through the egg coating so that its nucleus can fertilise the egg.

The researchers found that in the 140 men whose partners were undergoing IVF, higher lead levels in the seminal plasma correlated with low expression of mannose receptors and with inability of sperm to undergo mannose-induced acrosome reaction. Conversely, higher lead levels were associated with premature (or spontaneous) acrosome reaction that occurs before sperm-egg contact, also blocking fertilisation.

"To see whether this association between increased lead levels could be causal we exposed healthy sperm from nine fertile donors to increasing doses of exogenous lead to see what would happen. We got the same results," said Dr Benoff.

"These biomarkers provide relatively unambiguous endpoints for lead-induced reproductive toxicity and our data suggest that lead is acting at multiple levels in testis and sperm to decrease human male fertility.

"Our data also confirm that increased seminal plasma lead levels can occur without any detectable effects on male reproductive hormone function and also that they are associated with decreased sperm concentration, sperm shape, form and movement, suggesting that lead also acts in the testis. Elevated lead levels in rats' testes are associated with programmed cell death of sperm precursors and studies of men with non-obstructive low or zero sperm counts indicate that programmed cell death in the testes is a major determinant of sperm count in the ejaculate. This leads us to believe that lead is a contributory factor of declining sperm counts."

She said the findings of high seminal lead levels among the 140 men in the study were unexpected, as lifestyle questionnaires showed that none was engaged in occupations likely to produce exposure to metal ions. High lead levels in up to 29 of the IVF patients were associated with smoking and/or alcohol consumption, but high levels in patients who did not smoke cigarettes or drink alcohol were unexplained. One possibility was lack of exercise (blood lead levels increase with decreased physical activity). Another possibility was a low calcium or high lactose or fat diet, which can enhance lead accumulation. Genetic variation in response to lead exposure may also be a factor as the study revealed some instances of normal fertilisation rates despite high lead levels and reduced fertilisation rates despite low lead levels.

Dr Benoff said it was important that the results should not be construed as evidence of an epidemic of overt lead toxicity as none of the patients showed signs of lead toxicity and it is not yet known if there is a strong correlation between seminal plasma lead levels and lead concentration in the blood (the normal method of measuring lead exposure).

But she warned: "In the light of these results, environmental exposure limits for lead might be re-evaluated."

She said it was also important that men are often 'under served' at fertility clinics. "Our findings emphasise the need for co-operation between reproductive endocrinologists and urologists and a workup of the male partner of infertile couples that is more extensive than a simple semen analysis or measurement of circulating reproductive hormones. We suggest the addition of measurements of the heavy and transition metal ion content of seminal plasma (not blood) and some form of sperm function testing. It must be recognised that treating the male is generally less invasive and less costly than treating the female."


International Study Finds Mothers' Lifetime Lead Exposures May Put Breast-Fed Newborns At Risk

Results from a study conducted jointly by Australian and American scientists indicate that lead which has accumulated in a woman's bones from earlier exposures can be released during pregnancy and transferred to breast milk during lactation. This can translate into increased exposures for breast-fed infants whose mothers have a long-term history of lead exposure themselves.

The report appears today in the online version of the October issue of Environmental Health Perspectives, the monthly journal of the National Institute of Environmental Health Sciences. The study was co-funded by NIEHS and the National Institutes of Health's Office of Research on Minority Health.

"We should point out that breast feeding is still an important option for healthy mothers," said Brian Gulson, Ph.D., a toxicologist with Macquarie University in Sydney, Australia, and chief investigator for the project. "What we are saying is that breast-fed infants are only at risk if the mother has been previously exposed to high concentrations of lead from external sources such as leaded paint, pottery, or, in many other countries, industrial sources and leaded gasoline."

While previous research had demonstrated that lead is stored in bones, scientists could not quantify its release into the blood and other bodily fluids. To answer that question, the researchers compared second-generation Australian women with women who had migrated to Australia from Eastern Europe.

Since lead found in Eastern Europe has a slightly different atomic weight than lead found in Australia, the scientists were able to differentiate between skeletal lead deposits that had accumulated from the immigrants' earlier exposures while in their native country, and the lead burden received from more recent exposures. Hence, any circulating blood lead that matched the "Eastern European" profile could only be derived from skeletal stores.

Earlier data from the same study had shown that as much as 40 to 70 percent of the blood lead in pregnant women can come from lead that has accumulated in the bones. Additional analyses had revealed a significant increase in the mobilization of maternal skeletal lead during lactation. "Based on these observations, we wondered whether the infants born to these mothers might be at greater risk from breast feeding than from formula," said Gulson.

Because the study participants' blood lead concentrations were relatively low -- most had values less than 5 micrograms lead per deciliter (100 milliliters) of blood -- the lead concentrations in their breast milk were also low - 0.7 parts per billion on average. These concentrations were not significantly different from those found in various kinds of infant formulae.

In spite of these low concentrations, the researchers found a strong correlation between the amount of lead in the mothers' milk samples and the corresponding blood lead levels of the infants. In fact, calculations based on the first 60 to 90 days postpartum indicated that 36 to 80 percent of the infants' total blood lead was coming from breast milk or formula.

"Our data indicate that lead from urban air and water where these infants reside contributed negligibly to blood lead, while soil and dust were not considered to be relevant sources because these infants had not reached the stage of crawling and ubiquitous hand-to-mouth activity," said Gulson. "Therefore, we concluded that dietary lead was the primary source contributing to the body burden observed in these subjects, with a major part of the dietary lead ultimately derived from the mothers' bones."

The researchers also found a statistical link between the lead concentration in the maternal cord blood and lead levels in the first breast milk samples, a finding that could have clinical significance. Bill Jameson, Ph.D., the Institute toxicologist who serves as NIEHS project officer for the study, said "If this relationship can be verified through further investigations, then one could obtain an accurate estimate of an infant's lead exposure by simply testing the mother's blood lead."

The study also produced preliminary evidence suggesting that calcium supplementation can have a protective effect by slowing the release of lead from skeletal stores. The Australian researchers are planning additional NIEHS-funded studies to determine calcium's effectiveness in pregnant and nursing mothers.


Maternal Lead Exposure Linked To High Numbers Of Cavities

Exposure to high amounts of lead is likely one cause of the high rates of tooth decay found among certain groups, such as children raised in the inner city, according to a study in rats by University of Rochester dental researchers published in the September issue of Nature Medicine.

The scientists say that while lead does not actually cause cavities, it appears to make rats -- and thus people, whose teeth get cavities in an identical manner -- much more susceptible.

"This is one more compelling reason to get lead out of the environment," says lead investigator William Bowen, Margaret and Cy Welcher Professor of Dental Research and the founder of the Rochester Caries Research Center, the nation's first research center on tooth decay. Also working on the project were Gene Watson, assistant professor of clinical dentistry; graduate student Bianca Davis; Richard Raubertas, associate professor of biostatistics; and technician Sylvia Pearson.

Lead is well recognized as causing developmental and other problems. While lead has been removed from most gasoline, it's still present in old paint and commonly in soil or dust around contaminated buildings. Bowen says that the areas with the highest lead pollution -- inner cities and the Northeast -- mirror areas where dentists see the highest rates of tooth decay.

The team studied cavity susceptibility in rats born of mothers exposed to lead compared to offspring of rats not exposed to lead and found that offspring from exposed rats had 40 percent more cavities. The study, funded by the National Institute of Dental Research (NIDR), is the first to document the link between lead exposure and high cavity rates that a few small epidemiological studies have suggested.

The team is now searching for the cause. Some studies have suggested that lead interferes with the development of teeth. In humans lead is stored in the bones for decades, and higher amounts than normal are released into the blood of women who are pregnant. These high levels reach the fetus at a time critical to the development of teeth and salivary glands. The scientists discovered another possibility: They found that pups of exposed rats produced 30 percent less saliva, which protects teeth against cavities by neutralizing acids, providing minerals, and in many other ways. In addition, they detected levels of lead in the mothers' milk that were 10 times higher than the lead levels in their blood.

In an accompanying article in the journal, dentists Martin Curzon and Jack Toumba of the Leeds Dental School in the United Kingdom say this is the first time that scientists have pinpointed breast milk as a likely route of lead transfer from mother to offspring, and that reduced saliva flow has been implicated as a likely mechanism of decay in lead-induced cavities.

"Lead is not something that most dentists think of when they talk about the causes of cavities, but they should," says Watson. Poor hygiene, lack of dental care, and poor diet are still major concerns of dentists, as they should be, says Bowen. But he suggests that dentists who treat children from areas of high lead pollution should consider boosting standard preventive measures: fluoride treatments, check-ups, healthy diet, and dental sealants.

Lead is likely one reason why dental cavities are still a major problem in some pockets of the population despite the widespread use of fluoride and fluoridated toothpaste, Bowen says. While about half of 12 year olds in the U.S. are now free of cavities, 80 percent of the cavities in the group are seen in just one-fifth of the children. Ninety-five percent of all adults in the U.S. have cavities, which are a leading cause of tooth loss.

"There's a feeling among some people that dental caries is licked, that it's no longer a problem," says Bowen. "The fact is that it is still a serious public health problem in the U.S. and throughout the world."


Research shows low lead in body can cause spontaneous abortion

CHAPEL HILL, N.C. - Medical scientists have known for decades that high levels of lead in the body often cause spontaneous abortions, but now a new study shows that lower lead levels can produce that result too.

The risk of spontaneous abortion nearly doubles for every increase of five micrograms of lead per deciliter of blood, the research revealed.

Dr. Irva Hertz-Picciotto, professor of epidemiology at the University of North Carolina at Chapel Hill School of Public Health, Dr. Victor H. Borja-Aburto of Mexico's National Institute of Public Health and colleagues conducted the study. A report appears in the Sept. 15 issue of the American Journal of Epidemiology.

"We did this work because results of previous studies of low-level lead in pregnant women and spontaneous abortion were inconclusive," Hertz-Picciotto said. "The earlier research was not designed well enough to answer the question. This study is the best-designed so far and, we believe, does answer it. While further work is needed to confirm our results, it does appear that low to moderate lead can be a problem during pregnancy."

The project took place in Mexico City from 1994 to 1996. Investigators enrolled 668 women, who were interviewed, contributed blood specimens and were followed through home visits or telephone calls during their pregnancies. Mexico's respected National Institute of Neurology and Neurosurgery, which participates in the U.S. Centers for Disease Control and Prevention Blood Lead Proficiency Testing Program, analyzed the blood samples for lead. Another Mexican laboratory conducted analyses for signs of infection. Women averaged about 11 micrograms of lead per deciliter of blood, which is similar to average levels in the United States in the 1970s.

Researchers recorded whose pregnancies failed and whose did not and compared those records with subjects' blood lead levels. Thirty-six of 562 subjects still participating at five months gestation already had lost their babies.

"We did not find many infections that could cause spontaneous abortions, but we did find a dose response for lead," said Hertz-Picciotto, also a fellow at UNC-CH's Carolina Population Center. "That means that the more lead the women had in their systems, the greater the chance that they would spontaneously abort. The levels of lead in blood in our women were all below the acceptable standard for occupational exposures."

Most lead that Mexican women absorb comes from consuming food from ceramic cookware glazed with lead and from air pollution, she said. Another source may be husbands whose clothes become contaminated at work or whose semen is contaminated.

Since lead was eliminated from gasoline in the United States in the 1970s, levels of the toxic metal in U.S. residents have dropped over the past several decades except in certain subgroups, Hertz-Picciotto said. Among the chief sources of continued exposure in this country are air and soil pollution, lead-based paints in older homes and apartments and certain traditional ethnic remedies.

The new study indicates that exposures comparable to those of the U.S. general population in the 1970s and to many populations worldwide today can boost the risk of spontaneous abortion, the scientist said.

"These are far lower than exposures encountered in some occupations," she said.

The Mexican government funded the study. Scientists consider the research a landmark study since investigators measured blood lead levels before any pregnancies failed and avoided limitations of earlier work.

Lead at both high and low doses already has been shown to damage the nervous system and at high doses to injure the kidneys and reproductive systems, Hertz-Picciotto said. The metal easily crosses the placenta to developing infants.

Borja-Aburto earned his Ph.D. in epidemiology at UNC-CH's School of Public Health in 1995 and now directs the National Center of Environmental Health in Metepec, Mexico.


Vitamin C levels linked to amount of lead in blood

Despite the 1978 ban on lead-based paint for residential use, lead poisoning continues to be a serious public health threat, particularly for children because they are most susceptible to its effects.

In a new observational study, a pair of researchers at the San Francisco Veterans Affairs Medical Center and the University of California, San Francisco found that low levels of ascorbic acid (vitamin C) in the blood stream were associated with high blood levels of lead among Americans. The study's findings, which are published in the June 23 issue of the Journal of the American Medical Association (JAMA), also indicate that about half of one percent of all Americans (more than a million people) have elevated levels of lead in their blood.

According to the US Environmental Protection Agency, current studies suggest that the primary sources of lead exposure for most children are deteriorating lead-based paint, lead-contaminated dust, and lead-contaminated residential soil. Prior to 1978, lead was commonly used as a coloring agent and a stabilizer in paint.

"Vitamin C levels are an important independent correlate of blood lead levels among Americans," says Joel Simon, MD, MPH, SFVAMC staff physician and UCSF assistant professor of medicine, epidemiology & biostatistics. "To our knowledge, this report is the first population-based study to establish such an association. If a causal relation is confirmed, increased consumption of ascorbic acid may have public health implications for the prevention of lead toxicity."

The correlation between levels of vitamin C and blood lead levels is supported by the findings of a recent small clinical trial, conducted at the University of Texas Medical Branch in Galveston, that found that 1000mg vitamin C supplements decreased the blood lead levels of heavy smokers. Because smoking decreases the absorption and increases the metabolism of vitamin C, higher dietary vitamin C intake levels are recommended.

According to Simon, there are no acceptable levels of lead in humans. Symptoms of acute lead poisoning in adults include loss of appetite, abdominal pain, renal (kidney) disease, anemia, headache, memory loss, and peripheral neuropathy (pain, numbness, or tingling of the arms and legs). In children, signs of acute poisoning are anemia, abdominal pain and nervous system disorders. At sub-acute levels of lead poisoning, there are often no symptoms, but such levels can cause mental retardation, loss of cognitive function, language deficits, and behavior problems.

As a preventive measure, Simon recommends increasing the amount of fresh fruits and vegetables consumed everyday because of their vitamin C content as well as their many other nutritional benefits. "Humans are one of the very few mammals that do not produce vitamin C on their own," says Simon, "so all of it must be obtained from dietary sources." If people are concerned they are not receiving the proper amount of vitamins in their diets, Simon says a multiple vitamin or a modest dose vitamin C supplement may be taken as an 'insurance policy.'

The Recommended Daily Allowance (RDA) of vitamin C for non-smoking adults is 60 mg and 100 mg for smokers. The RDA for children is 45 mg. However, new dietary reference intakes for vitamin C, such as the estimated average requirement level, are currently being formulated and are likely to be higher. As a point of reference, a medium size orange contains 60 to 80 mg of vitamin C, and one cup of freshly squeezed orange juice has about 120 mg of the vitamin.

According to Simon, there are very few negative effects of too much vitamin C.

However, he says intakes of 1000 mg will result in saturation of the plasma in the blood stream. Larger intakes are probably not indicated and are passed from the body in the stool and in urine. Mega-doses of vitamin C (3000 mg or more) can cause diarrhea and stomach cramps. And while persons with hemochromatosis, a hereditary iron-storage disorder, should not be discouraged from eating fresh fruits and vegetables, they should be cautious about consuming supplements containing more than 500 mg of vitamin C because vitamin C enhances iron absorption and could worsen this condition.

The investigators studied data gathered by the Third National Health and Nutrition Examination Survey, 1988-1994 (NHANES III). The national probability survey of Americans employed a stratified, cluster sampling design. After excluding some participants because of reported histories of lead poisoning, or questionable or missing information, the researchers used statistical methods to calculate their findings. In all, data from more than 19,500 Americans were analyzed.


Lead accelerates aging process years after exposure

ST. PAUL, MN - Lead exposure on the job can cause progressive declines in memory and learning abilities nearly two decades later, according to a study in the October 24 issue of Neurology, the scientific journal of the American Academy of Neurology.

The study compared 535 former chemical manufacturing employees exposed to lead at work to 118 non-exposed people from the same neighborhoods.

"The effects of the average level of bone lead found in former lead workers was like five more years of aging on the brain," said Brian Schwartz, MD, of Johns Hopkins School of Hygiene and Public Health in Baltimore, MD.

The study participants were followed for four years, undergoing two to four sets of neurological tests with an average of one year between tests. The former workers had an average of 8 years of occupational exposure to lead with an average of 16 years since last working with lead.

The first year of the study, lead levels were determined through blood tests, while follow up visits measured lead levels in bone through a technique called x-ray fluorescence.

"The higher the peak level of lead determined in former lead workers, the greater the decline in brain functions," Schwartz said. "Since these declines were seen long after exposure to lead had stopped, it suggests that the effect of lead on the brain is progressive."

The workers not only had greater declines in test scores due to lead, but also in normal age-related declines in brain functions, Schwartz said.

Significant differences were discovered between the former workers and other participants in tests involved in visual construction, verbal memory and learning, visual memory, planning and organizational ability, and manual dexterity.

"We know there's a decline in brain power as we get older -- generally we call this 'normal aging,'" said Schwartz. "Most of the research has been about how chemicals, like lead, affect kids. This is the first study to explore long-term problems caused by exposure to chemicals as adults. Some of what we have been calling 'normal aging' may in fact be due to past exposures to chemicals or other agents that can affect the central nervous system. This is potentially a very important health problem."


 

 

 


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