More research should focus on BPA and health effects in adults

In one of the first human studies of its kind, researchers have found that urinary concentrations of the controversial chemical Bisphenol A, or BPA, may be related to decreased sperm quality and sperm concentration.

However, the researchers are quick to point out that these results are preliminary and more study is needed. Several studies have documented adverse effects of BPA on semen in rodents, but none are known to have reported similar relationships in humans.

BPA is a common chemical that’s stirred much controversy in the media lately over its safety. Critics say that BPA mimics the body’s own hormones and may lead to negative health effects. BPA is most commonly used to make plastics and epoxy resins used in food and beverage cans, and people are exposed primarily through diet, although other routes are possible. More than 6 billion pounds of BPA are produced annually.

The new study suggests that more research should focus on BPA and health effects in adults, says John Meeker, assistant professor of Environmental Health Sciences at the University of Michigan School of Public Health.

Meeker is the lead author on the study, along with Russ Hauser, the Frederick Lee Hisaw Professor of Reproductive Physiology at Harvard School of Public Health. Colleagues at Massachusetts General Hospital and the U.S. Centers for Disease Control and Prevention also contributed to the research.

“Much of the focus for BPA is on the exposures in utero or in early life, which is of course extremely important, but this suggests exposure may also be a concern for adults,” Meeker said. “Research should focus on impacts of exposure throughout multiple life stages.” Meeker and Hauser recruited 190 men through a fertility clinic. All gave spot urine samples and sperm samples the same day. Subsequently, 78 of the men gave one or two additional urine samples a month apart. Researchers detected BPA in 89 percent of the urine samples.

Researchers measured sperm concentration, sperm motility, sperm shape and DNA damage in the sperm cell.

“We found that if we compare somebody in the top quartile of exposure with the lowest quartile of exposure, sperm concentration was on average about 23 percent lower in men with the highest BPA,” Meeker said.

Results also suggested a 10 percent increase in sperm DNA damage.

The results are consistent with a previous study by Meeker and Hauser suggesting that certain hormones, specifically FSH (follicle-stimulating hormone) and Inhibin B, are elevated or decreased in relation to BPA, respectively, a pattern consistent with low sperm production and development.

Meeker stressed that further study is necessary due to the study’s relatively small sample size and design.

“The study from which these data came is currently in progress,” Hauser said. “With a larger sample size and enhanced study design, we will be able to more definitively investigate this preliminary association in the near future.”

Reference:

University of Michigan, Sperm may be harmed by exposure to BPA, study suggests, ANN ARBOR, Mich., Aug. 3, 2010.

Related EMM Articles about BPA:

• Lawsuit seeks to ban BPA from food packaging
• 60 Scientists and NGOs Sound Joint Warning on Plastics Chemical
• Everyday Exposure to Dangerous Levels of Toxic Chemical BPA Unavoidable
• Yale: Why BPA leached from ’safe’ plastics may damage health of female offspring
• Study shows: Plastics chemical retards growth, function of adult reproductive cells

NRDC Sues Food and Drug Administration for Failure to Regulate Toxic Chemical

WASHINGTON – - The Natural Resources Defense Council filed a lawsuit against the Food and Drug Administration for its failure to act on a petition to ban the use of bisphenol A (BPA) in food packaging, food containers, and other materials likely to come into contact with food. BPA, a hormone-disrupting chemical linked to serious health problems, poses a particular risk to fetuses, infants and young children. NRDC filed today’s lawsuit in U.S. Court of Appeals for the D.C. Circuit.

In October 2008, NRDC petitioned the FDA to prohibit the use of BPA in food packaging to prevent the toxic chemical from contaminating food. The FDA has failed to take action in response to the petition for more than 18 months, although the agency expressed concern about the effects of early life exposure to BPA on brain development and the prostate gland of fetuses, infants, and children.

BPA is found in wide variety of products, including the lining of liquid infant formula cans, soda or beer cans, fruit or vegetable cans, and pizza boxes as well as consumer products made from polycarbonate plastics, including baby bottles, sippy cups, and reusable water bottles. More than 93 percent of the general population has some BPA in their bodies, primarily from exposure through food contamination and other preventable exposures.

“BPA-free alternatives are already available and on the market. The FDA has no good reason to drag their feet on banning it,” said Dr. Sarah Janssen, a senior scientist in the Environment and Public Health program at NRDC. “It’s upsetting that food is most people’s primary source of exposure to BPA. The FDA should act now to eliminate this unnecessary risk.”

A growing amount of scientific research has linked BPA exposure to altered development of the brain and behavioral changes, a predisposition to prostate and breast cancer, reproductive harm, diabetes, obesity, and cardiovascular disease.

“The FDA has failed to safeguard the food supply and protect the public from harm,” said Aaron Colangelo, an attorney with NRDC. “The FDA’s failure to regulate this chemical in food packaging in unjustified, and so we are forced to ask the court to intervene and order the agency to take action

Literature:

NRDC, Natural Resources Defense Council, Release – Lawsuit Seeks to Ban BPA from Food Packaging, WASHINGTON, June 29, 2010.

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The Natural Resources Defense Council is a national, nonprofit organization of scientists, lawyers and environmental specialists dedicated to protecting public health and the environment. Founded in 1970, NRDC has 1.3 million members and online activists, served from offices in New York, Washington, Chicago, Los Angeles, San Francisco and Beijing.

Scientists and NGOs concerned about the health impacts of bisphenol A

PRESS RELEASE, 23rd JUNE 2010

An unprecedented 60 scientists and international environment, health and women’s organisations from around the globe have jointly written to the European Food Safety Authority (EFSA) stating that

“action is necessary to reduce the levels of Bisphenol-A (BPA) exposure, particularly in groups at highest risk, namely young infants and pregnant mothers.”

[Quotes from some of the participating scientists and NGOs can be found towards the end of this release.]

In total, 41 NGOs and 19 scientists from 15 countries from across the globe (including 9 from the UK) have signed the letter. The letter comes on the eve of a new scientific opinion to be released by the EFSA on the safety of Bisphenol A in food contact materials expected in early July 2010. EFSA was requested by the European Commission to assess the latest science on Bisphenol A, and if necessary, to update the existing Tolerable Daily Intake (TDI) (a specific amount in food or drinking water that can be ingested (orally) over a lifetime without an appreciable health risk).

Bisphenol A is a mass produced chemical used in the manufacture of polycarbonate plastics that are clear and nearly shatter-proof. It can be found in plastics used for food and beverages, such as baby bottles, sports water bottles, as an epoxy resin in canned food and drinks, plastic food storage containers, tableware and in other products, including dental sealants, and has been found to leach into food and drink.

There have been long standing concerns about the health impacts of bisphenol A, due to scientific studies that have shown it has hormone disrupting effects at extremely low levels of exposure. Human bio-monitoring studies have shown that the vast majority of people in developed countries are exposed to Bisphenol-A.

EFSA’s previous opinions in 2007 and 2008 predominantly relied upon a handful of industry backed scientific papers that have expressed no concerns about our levels of BPA exposure. The letter from scientists and NGOs highlights scientific criticism in academic journals regarding these papers as compared to the “several hundred peer reviewed scientific papers have been published that have highlighted potential adverse health effects associated with BPA exposures”

The letter also draws attention to some of the new studies which have raised risks of exposure relating to a potential increased likelihood of developing ‘diabetes’, ‘developmental programming’ and ‘breast cancer’. Bisphenol A exposure at environmentally relevant levels commonly found in the environment in developed countries has also been repeatedly linked by independent university – based scientists to a number of other serious chronic health conditions.

Despite EFSA’s pivotal position in setting chemical food safety levels across the EU, Sweden and Germany have become the third and fourth most recent EU member states, alongside France and Denmark, to take action ahead of the EFSA review.

Andreas Carlgren, Sweden’s Environment Minister stated, on 11th May 2010, that

“If the EU will not quickly forbid the hormone disrupting substance bisphenol in baby-bottles Sweden will precede with a national prohibition.”

The President of the German Federal Environment Agency on the 9th June also broke from EFSA policy by issuing new guidance calling on

“manufacturers, importers and users of bisphenol A to use alternative substances that pose less risk to human health and the environment in all areas of use that significantly contribute to exposure”.

Regulators in Canada and the USA have already taken action to limit BPA exposure, for example in its use in baby bottles. As yet there has been no similar action at the European Union level.

A number of EU member states continue to back a common approach across the EU on bisphenol A. Tim Smith, the head of the UK Food Standards Agency, declared in an internal FSA report on the 12th May, 2010 that he ‘considers it important to have an agreed position across the EU’ and that the FSA will only ‘revise our position in line with it the EFSA Review if it is considered necessary’, despite the action that is being taken elsewhere across the EU.

The EFSA have already delayed publication of its review, as explained on its website:

To give the European Commission an up-to-date overview of the safety of BPA, EFSA will now deliver a scientific opinion in early July rather than end of May. This is due to the need for the Panel to consider hundreds of studies in its review and analysis of the most recent scientific literature.

The letter from scientists and organisations opens by ‘welcoming this announcement’ issued at the 11th hour that EFSA has finally agreed to examine hundreds of non-industry backed scientific papers.

The letter was drafted by Breast Cancer UK and Prof. Fredrick vom Saal, Curators Professor of Biological Sciences, University of Missouri-Columbia who has been awarded by his peers for his work on Bisphenol-A and is a recognised leader in this field. The effort was also coordinated by the Brussels based Health and Environment Alliance (HEAL).

Prof. vom Saal stated in response to the publication of the letter that:

“At the heart of the debate over BPA lies an outdated set of guidelines used by regulatory agencies that are based on approaches to evaluating the safety of chemicals established over 50 years ago. Thus, 21st century research approaches have provided overwhelming scientific evidence of harm in hundreds of published reports, but these findings are being rejected for consideration because they do not conform to the outdated testing guidelines.

“This has left regulatory agencies to rely entirely on industry-funded research that used ‘approved’ testing methods that are crude and insensitive, and it is not surprising that 100% of these industry-funded studies conclude that BPA causes no harm.

“The only rational path for European regulators is to take decisive action to reduce human exposure to BPA. The overwhelming nature of the total scientific evidence mandates this as a priority.”

Clare Dimmer, Chair of Trustees Breast Cancer UK and former breast cancer patient stated:

“Breast cancer is the most common cancer across Europe and has been increasing rapidly regardless of the costly and expensive efforts made by Governments to improve screening, treatment, and increase research. It must now be time that regulators act on the science and begin to take a precautionary approach to hazardous chemicals like bisphenol-A found in our everyday products.”

Lisette van Vliet, Ph.D. the Toxics Policy Advisor at HEAL said:

“It is high time that EFSA caught up to the overwhelming science showing genuine reasons for concern about our daily exposure to BPA.”

Participating scientists and organisations were given the opportunity to provide a quote for this press release; those that responded have been included below. This does not preclude participating organisations providing their own releases, supporting statements and additional comments.

Prof. Andrew Watterson, Occupational and Environmental Health Research Group, University of Stirling, said:

“It’s worrying, considering the weight of the scientific evidence, that strong action to reduce human exposure is yet to be taken. Hundreds of academic studies have explicitly raised the risks of developmental harm to foetuses and young children from exposure to BPA and this should dictate a strong precautionary policy response from European regulators. If this is not forthcoming, the UK Government must intervene as other European countries are already doing so.”

Daniela Hoffmann, Chemicals Expert, GLOBAL 2000/Friends of the Earth Austria:

“EFSA has to finally acknowledge the overwhelming scientific evidence concerning the risk BPA poses to human health.”

Sarah Häuser, Chemicals Expert BUND / Friends of the Earth Germany:

“The existing Tolerable Daily Intake for BPA does not protect human health. In animal experiments and biomonitoring studies, BPA doses much smaller than those estimated as being safe by EFSA were linked to chronic conditions health damages like diabetes and cardiovascular diseases. It’s time to take action now.”

For further information please contact:

Hratche Koundarjian, Campaign Manager, Breast Cancer UK, Charity No: 1088047, T: 07905 911 039, E: hratche@breastcanceruk.org.uk, W: www.breastcanceruk.org.uk / www.nomorebpa.org.uk

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Letter and Signatories:

Prof. Klaus-Dieter Jany, Chair of the CEF Panel

European Food Safety Authority

Largo N. Palli 5/A, 43121 Parma, Italy

23rd June 2010

Dear Prof. Jany,

We are writing to welcome the announcement on the European Food Safety Authority (EFSA) website that the CEF panel will be considering ‘hundreds of studies in its review and analysis of the most recent scientific literature’ in its review of the TDI of bisphenol-A in food contact products.

Over the last decade and a half, a substantive body amounting to several hundred peer reviewed scientific papers, have been published that have highlighted potential adverse health effects associated with BPA exposures, at internal doses relevant to levels of biologically active BPA found in humans.

As a March 2010 Review (Vandenberg et al) of 80 bio-monitoring studies of BPA in Environmental Health Perspectives makes clear;

‘The two toxicokinetic studies performed to date, which suggest that human exposure is negligible, have significant flaws and are therefore not reliable for risk assessment purposes.’

However, in its prior risk assessments of BPA, EFSA only relied on a small number of studies rather than the much larger number that the United States Food and Drug Administration recently recognised as valid and of high utility in its risk assessment of BPA, and which led the FDA to express concern about the health hazards posed by BPA.

Only a tiny minority of studies have articulated that BPA exposure is completely safe, and many of these research papers have been criticised in academic commentaries and responses as having serious flaws, but it is these few flawed studies that EFSA previously relied on to declare BPA safe.

For example, a letter co-authored by 24 scientists published in the February 2010 edition of Toxicological Sciences states;

‘Publishing studies that conclude no harm in response to low doses of endocrine disrupting chemicals, when the studies did not include a positive control (Tyl et al., 2002), included inappropriate doses of positive controls (Ryan et al., 2009; Tyl et al., 2008), or included positive controls that showed no effect (Cagen et al., 1999), is inappropriate in peer-reviewed journals (Myers et al., 2009a,b; vom Saal and Welshons, 2006). Such studies violate basic principles of study design.’

Many scientific studies are now calling into question the safety of BPA. For example, a recent study has highlighted that BPA may contribute to metabolic disorders relevant to glucose homeostasis, and suggests that BPA may be a risk factor for diabetes (Alonso-Magdalena et al., 2010). Moreover, experiments at Yale university report that BPA may induce altered developmental programming (Bromer et al.,2010), and Doherty et al (2010) of Yale university have published a study which raises the concern about epigenetic effects of BPA on the regulation of the mammary gland, with potential implications for breast cancer risk. Endometriosis is also a concern as work by Signorile et al (2010) highlights that pre-natal exposure of mice to bisphenol-A causes an endometriosis-like response in female offspring.

It is therefore our opinion that any objective and comprehensive review of the scientific literature will lead to the conclusion that action is necessary to reduce the levels of BPA exposure, particularly in groups at highest risk, namely young infants and pregnant mothers.

There are an increasing number of countries that are either already committed to this course of action, or have signalled that they will soon be undertaking similar measures.

We share the concerns of these Governments and regulators and believe that reducing BPA exposure to these groups is both scientifically sound and in the best interest of public health.

As such, we call on you as the Chair of the CEF panel and the CEF Committee Members in their ongoing review to include all relevant studies, including bio-monitoring studies, and based on that evidence we conclude that there is a strong scientific mandate for action.

Yours sincerely,

1. Benson Akingbemi, Associate Professor, Department of Anatomy, Physiology and Pharmacology, Auburn University, Auburn, USA.
2. Prof. Dr. Ibrahim Chahoud, Institute of Clinical Pharmacology and Toxicology, Dept. of Toxicology, Charité – Universitätsmedizin Berlin
3. André Cicolella, Dipl Eng chemist-toxicologist.
4. Prof. Patricia Hunt, Meyer Distinguished Professor, School of Molecular Biosciences, Washington State University
5. Prof. Maricel V. Maffini. Ph.D. Research Assistant Professor. Department of Anatomy and Cellular Biology, Tufts University School of Medicine
6. Jane Muncke, Ph.D, Environmental Toxicologist, Emhart Glass SA, Switzerland.
7. John Peterson Myers, Ph.D., Chief Scientist, Environmental Health Sciences, Charlottesville VA.
8. Angel Nadal, PhD, Professor of Physiology, Instituto de Bioingeniería and CIBERDEM, Universidad Miguel Hernández de Elche, Spain.
9. Dr John Newby, Medical Information Scientist for the Cancer Prevention Society and Former Member of the Developmental Toxico-Pathology Research Group, Department of Human Anatomy & Cell Biology, Faculty of Medicine, University of Liverpool.
10. Prof. Jörg Oehlmann, Goethe University Frankfurt am Main, Institute for Ecology, Evolution and Diversity.
11. Prof. Gail S. Prins, PhD, Professor of Physiology, Department of Urology, University of Illinois at Chicago.
12. Prof. Fredrick vom Saal, Curators Professor of Biological Sciences, University of Missouri-Columbia.
13. Prof. Pietro Giulio Signorile, President of the Italian Endometriosis Foundation.
14. Prof. Ana M Soto, MD, Department of Anatomy and Cell Biology, Tufts University, School of Medicine.
15. Prof. Hugh S. Taylor, M.D., Professor of Molecular, Cellular and Developmental Biology, Department of Obstetrics, Gynecology and Reproductive Sciences, Yale University.
16. Laura N. Vandenberg, PhD, Postdoctoral Fellow, Center for Regenerative and Developmental Biology, Tufts University.
17. Prof. Cheryl S. Watson, PhD, Professor, Biochemistry & Molecular Biology Dept. University of Texas, Medical Branch, Galveston.
18. Prof. Andrew Watterson, Occupational and Environmental Health Research Group, University of Stirling.
19. Prof. R. Thomas Zoeller, Biology Department, Morrill Science Center, University of Massachusetts.

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1. Action for Breast Cancer, Malta
2. Alliance for Cancer Prevention, UK
3. Arnika, Czech Republic
4. Association for Environmental and Chronic Toxic Injury, Italy
5. Austrian section of ISDE (International Society of Doctors for the Environment), Austria
6. Breast Cancer Fund, USA
7. Breast Cancer UK, UK
8. BUND / Friends of the Earth Germany, Germany
9. Cancer Prevention and Education Society, UK
10. ChemSec –International Chemical Secretariat, International
11. CHEM Trust, UK
12. Chemical Sensitivity Network, Germany
13. Clean Air Action Group, Hungary
14. Comité pour le Développement Durable en Santé, France
15. Danish Consumer Council, Denmark
16. The Danish Ecological Council, Denmark
17. Eco-Accord Program on Chemical Safety, Eastern Europe, Caucasus and Central Asia
18. EcoAid, Germany
19. Ecologistas en Acción, Spain
20. Environmental Health Fund, USA
21. Environment Illinois, USA
22. European Environmental Bureau, EU
23. Finnish Association for Nature Conservation, Finland
24. Friends of the Earth Spain, Spain
25. Global 2000 / Friends of the Earth Austria, Austria
26. Health and Environmental Network, Europe
27. Health Care Without Harm, International
28. Indiana Toxics Action, USA
29. Instituto Sindical de Trabajo Ambiente y Salud, Spain
30. The Irish Doctors’ Environmental Association, Ireland
31. Italian Endometriosis Foundation, Italy
32. Plastic Planet, Austria
33. Rachel’s Friends Breast Cancer Coalition, USA
34. Réseau Environnement Santé, France
35. Society for Sustainable Living, Czech Republic
36. Unison, UK
37. VHUE e.V., Germany
38. Women in Europe for a Common Future, Europe
39. Women’s Environmental Network, Scotland
40. Women’s Voices for the Earth, USA
41. WWF European Policy Office, Europe

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References

• Vandenberg LN, Chauhoud I, Heindel JJ, Padmanabhan V, Paumgartten FJ, Schoenfelder G 2010. Urinary, Circulating and Tissue Biomonitoring Studies Indicate Widespread Exposure to Bisphenol A. Environ Health Perspect :-. doi:10.1289/ehp.0901716
• vom Saal FS, Akingbemi BT, Belcher SM, Crain DA, Crews D, Guidice LC, Hunt PA, Leranth C, Myers JP, Nadal A, Olea N, Padmanabhana V, Rosenfeld CS, Schneyer A, Schoenfelder G, Sonnenschein C, Soto AM, Stahlhut RW, Swan SH, Vandenberg LN, Wang H, Watson CS, Welshons WV and Zoeller RT. 2010. Flawed Experimental Design Reveals the Need for Guidelines Requiring Appropriate Positive Controls in Endocrine Disruption Research. Toxicological Sciences 2010 115(2):612-613; doi:10.1093/toxsci/kfq048
• Alonso-Magdalena P, Vieira E, Soriano S, Menes L, Burks D, Quesada I, et al. 2010. Bisphenol-A Exposure during Pregnancy Disrupts Glucose Homeostasis in Mothers and Adult Male Offspring. Environ Health Perspect :-. doi:10.1289/ehp.1001993
• Bromer JG, Zhou Y, Taylor MB, Doherty L, Taylor HS. Bisphenol-A exposure in utero leads to epigenetic alterations in the developmental programming of uterine estrogen response. FASEB J. 2010 Feb 24. [Epub ahead of print] PubMed PMID: 20181937.
• Doherty L, Bromer JG, Zhou Y, Aldad TS and Taylor HS. In Utero Exposure to Diethylstilbestrol (DES) or Bisphenol-A (BPA) Increases EZH2 Expression in the Mammary Gland: An Epigenetic Mechanism Linking Endocrine Disruptors to Breast Cancer. Hormones and Cancer. DOI: 10.1007/s12672-010-0015-9.
• Signorile PG, Spugnini EP, Mita L, Mellone P, D’Avino A, Bianco M, Diano N, Caputo L, Rea F, Viceconte R, Portaccio M, Viggiano E, Citro G, Pierantoni R, Sica V, Vincenzi B, Damiano G. Mita DG, Baldi F and Baldi A. Pre-natal exposure of mice to bisphenol A elicits an endometriosis-like phenotype in female offspring. General and Comparative Endocrinology. doi:10.1016/j.ygcen.2010.03.030.

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German Translation by CSN:

60 Wissenschaftler und NGOs appellieren an EFSA

In an article to be published on 21 June 2010 in the Journal of Clinical Oncology, researchers from Inserm (Inserm unit 625 – Research Group on Human and Mammalian Reproduction, University of Rennes 1), the CHU (University Hospital Centre) in Pointe à Pitre (urology department, University of the French West Indies and Guiana) and from the Center for Analytical Research and Technology (University of Liège, Belgique), show that exposure to chlordecone (also named Kepone), an organochlorine chemical with well defined estrogenic properties used in the French West Indies until 1993, is associated to a significant increased risk of prostate cancer.

Chlordecone is an organochlorine insecticide used in the French West Indies from 1973 to 1993 to control the banana root borer. Permanently polluted soils and waters have remained the primary source of foodstuff contamination, and humans being continue to be exposed to this chemical. Chlordecone is recognized as endocrine disruptor, and is classified by IARC/WHO as possibly carcinogenic to humans.

Research results to be published in the Journal of Clinical Oncology come from an interdisciplinary prostate cancer epidemiology program named Karuprostate (from Karukera, the original Caribbean name of Guadeloupe). A case control study compared the characteristics of 709 consecutive incident cases of prostate cancer and 723 controls without prostate cancer. One of the main objectives of the research programme was to test the hypothesis that chlordecone exposure favors the development of prostate cancer in the French West Indies. Chlordecone exposure was evaluated by measuring its concentration in the blood.

The analysis of the results by the researchers shows that chlordecone exposure is associated to a significant increase in the risk of prostate cancer with increasing plasma chlordecone concentration. These results are supported by the fact that men, presenting genetic variations which reduce their ability to eliminate the molecule, have higher risk of developing the disease.

The prostate cancer risk associated with chlordecone exposure was higher in subjects with a family history of prostate cancer first-degree relatives. Moreover, the prostate cancer risk associated with chlordecone exposure was particularly marked in subjects who had spent some time living in a Western country. According to the authors, several explanations may be given:

“The interaction of family history with prostate cancer may be explained by the presence of genetic susceptibility factors which are common both to the disease and to the chlordecone metabolic pathway but also by similar patterns of exposure, shared by members of a same family”.

“Migration constitutes a period of exposure to specific environmental risk factors, including hazardous chemicals or nutritional agents. Residing in Western countries may induce significant changes in an individual, due, for example, to the adoption of a Western lifestyle, including, in particular, eating habits that may be risk factors for prostate cancer”

These results are the first to suggest that there is a causal relationship between chlordecone exposure and prostate cancer risk, and support the hypothesis that environmental estrogens may be involved in the development of prostate cancer. Such a relationship may be affected by genetic background, together with environmental agents related to diet or lifestyle.

Literature: INSERM (Institut national de la santé et de la recherche médicale), Chlordecone exposure and risk of prostate cancer, June 22, 2010.

Berkeley — Pregnant women with higher blood levels of a common flame retardant had altered thyroid hormone levels, a result that could have implications for fetal health, according to a new study led by researchers at the University of California, Berkeley.

“This is the first study with a sufficient sample size to evaluate the association between PBDE flame retardants and thyroid function in pregnant women,” said the study’s lead author, Jonathan Chevrier, a UC Berkeley researcher in epidemiology and in environmental health sciences. “Normal maternal thyroid hormone levels are essential for normal fetal growth and brain development, so our findings could have significant public health implications. These results suggest that a closer examination between PBDEs and these outcomes is needed.”

PBDEs, or polybrominated diphenyl ethers, are a class of organobromine compounds found in common household items such as carpets, textiles, foam furnishings, electronics and plastics. U.S. fire safety standards implemented in the 1970s led to increased use of PBDEs, which can leach out into the environment and accumulate in human fat cells.

Studies suggest that PBDEs can be found in the blood of up to 97 percent of U.S. residents, and at levels 20 times higher than those of people in Europe. Because of California’s flammability laws, residents in this state have some of the highest exposures to PBDEs in the world.

“Despite the prevalence of these flame retardants, there are few studies that have examined their impact on human health,” said the study’s principal investigator, Brenda Eskenazi, UC Berkeley professor of epidemiology and of maternal and child health. “Our results suggest that exposure to PBDE flame retardants may have unanticipated human health risks.”

The new study, to be published June 21 in the journal Environmental Health Perspectives, is the second study to come out this year from Eskenazi’s research group linking PBDEs to human health effects. Eskenazi was the principal investigator on the earlier study that found that women with higher exposures to flame retardants took longer to get pregnant.

In the new study, the researchers analyzed blood samples from 270 women taken around the end of their second trimester of pregnancy. The women in the study were part of a larger longitudinal study from the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) that examines environmental exposures and reproductive health.

The researchers measured concentrations of 10 PBDE chemicals, two types of thyroxine (T4) and thyroid-stimulating hormone (TSH). They controlled for such factors as maternal smoking, alcohol and drug use, and exposure to lead and pesticides.

Analysis focused on the five PBDE chemicals that were detected most frequently and are components of a mixture called pentaBDE. The researchers found that a 10-fold increase in each of the PBDE chemicals was associated with decreases in TSH ranging from 10.9 percent to 18.7 percent. When the five PBDEs were analyzed together, a tenfold increase was linked to a 16.8 percent decrease in TSH.

The study did not find a statistically significant effect of PBDE concentrations on levels of T4. With one exception, all the women in the study with low TSH levels had normal free T4 levels, which corresponds to the definition of subclinical hyperthyroidism. The study found that odds of subclinical hyperthyroidism were increased 1.9 times for each tenfold increase in PBDE concentrations.

“Low TSH and normal T4 levels are an indication of subclinical hyperthyroidism, which is often the first step leading toward clinical hyperthyroidism,” said Chevrier. “Though the health effect of subclinical hyperthyroidism during pregnancy is not well understood, maternal clinical hyperthyroidism is linked to altered fetal neurodevelopment, increased risk of miscarriage, premature birth and intrauterine growth retardation.”

Exactly how flame retardants influence TSH levels is unclear, the researchers said, but animal studies have shown that certain PBDEs can mimic thyroid hormones.

In addition to the commercial mixture pentaBDE, octaBDE and decaBDE have been developed for use as commercial flame retardants. PentaBDE and octaBDE have both been banned for use by the Stockholm Convention on Persistent Organic Pollutants, the European Union and eight U.S. states, including California, but they are still present in products made before 2004.

The production of decaBDE by major manufacturers is scheduled to be phased out in the United States by 2013. However, pentaBDE and decaBDE are being replaced by new brominated and chlorinated compounds whose impact on human health is not yet clear, the researchers noted.

Literature: University of California – Berkeley, Flame retardant linked to altered thyroid hormone levels during pregnancy, June, 21, 2010.