Breast milk contains flame retardants with exposure patterns similar to phased-out PBDEs.
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Abou-Elwafa Abdallah, M, and S Harrad. 2010. Tetrabromobisphenol-A, hexabromocyclododecane and its degradation products in UK human milk: Relationship to external dose. Environment International http://dx.doi.org/10.1016/j.envint.2010.11.008. |
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Context
Flame retardant chemicals are added to numerous types of plastics and textiles to reduce their flammability and meet government safety standards. They are used in and on many consumer products, including furniture, curtains, appliances, electronics and building materials.
However, these chemicals can migrate out of the treated products. They can accumulate in indoor air and dust, and ultimately, lead to exposure in people, through eating, breathing and ingesting dust. Of particular concern are children, who often put items in their mouths and spend more time on floors and other dusty surfaces, resulting in greater exposure to chemicals found in dust.
PBDEs – a class of brominated flame retardants – were added to polyurethane foam used in furniture and in some electronic products to reduce flammability. About a decade ago, many government regulatory agencies took steps to ban and prohibit the use of PBDEs. In 2004, two of the three commercial PBDE mixtures were phased out from use in the United States and Europe.
Before the ban, PBDE levels were increasing in human tissues. Animal studies showed the chemicals could cause neurodevelopmental problems and affect thyroid hormone regulation.
Human studies published in the past year find that children born with higher levels of PBDEs in their blood are more likely to perform lower on mental and developmental tests as they grow older. A few other studies have determined that PBDEs in the blood are significantly associated with the levels of thyroid hormones. Altered levels of thyroid hormones may affect growth and development, particularly in pregnant women (Turyk et al. 2008; Herbstman et al. 2010; Chevrier et al. 2010).
Despite the phase-out, PBDEs still contaminate products, homes and people. PBDEs are found in more than 99 percent of the U.S. population. Levels measured in children are much higher than adult levels.
Consumer products also contain other types of brominated flame retardants, such as hexabromocyclododecane (HBCD) and tetrabromobisphenol-A (TBBP-A). HBCD is commonly used in polystyrene insulation found in most residential and public buildings and has limited applications in textiles, such as curtains. TBBPA is more commonly applied to printed circuit boards in electronic items.
Studies have found HBCD in the environment, particularly in marine mammal tissues, such as dolphins and seals. They have been detected in fat, blood and breast milk from people in the United States, Canada, Europe and Japan. Animal research suggests HBCDs can affect reproduction and the brain. Next to nothing is known about whether HBCDs may affect human health.
What did they do?
Scientists at the University of Birmingham in the United Kingdom collected 34 samples of human milk from women who lived in Birmingham, U.K.
They analyzed the samples for two different classes of brominated flame retardants: HBCD and TBBP-A. They tested the milk for three types of HBCDs and several of the HBCDs degradation products.
The researchers also estimated through computer models the infant's daily exposure to HBCD. They compared this value with exposure estimates for adults.
What did they find?
HBCDs were found in every sample of human milk examined in the study, whereas TBBP-A was found in about one-third of the samples.
Surprisingly, HBCD levels were very similar to previous reports of PBDEs in breast milk from this region, about 6 parts per billion (ppb). TBBP-A was found at much lower levels of about 0.06 ppb.
HBCD degradation products were detected in more than half the samples, but at concentrations about 100 times less than that of the HBCDs. It is unclear whether these HBCD degradation products are the result of metabolism of the HBCDs in the body or from their uptake from the environment. No information is available on the toxicity or health effects of these degradation products.
Based on this data, an infant's exposure to the HBCDs from drinking breast milk was estimated to be four times higher than an adult's combined exposure to HBCDs from diet, breathing and ingesting dust. In adults, most exposure to HBCDs occurs from both diet and dust ingestion. Exposure from diet is approximately three times higher than from dust. The estimated half-life of HBCDs in the body is approximately 165 days.
What does it mean?
A different class of brominated flame retardants is reported in human breast milk in the United Kingdom, adding yet another country to a growing list of places where the chemicals contaminate people.
This study raises concerns about increasing exposures to additional classes of brominated flame retardants. Higher exposures are especially troubling for infants and children who generally face the greatest health risks from chemical exposures.
In this study, the researchers estimated that levels of the HBCDs and TBBA-A reaching the infants through breast milk were well above – about four times higher for HBCDs – the estimated exposures to adults and toddlers in the United Kingdom. While this indicates that infants will be exposed to HBCD from breast milk intake, breast feeding is still highly recommended for its known health benefits.
Levels of the three types of HBCDs and TBBA-A measured in this study reflect increased use of the flame retardants in consumer products. It appears that HBCDs use and exposure levels are following the same trend as PBDEs in breast milk – as use increases so do exposures.
More time and research is needed to determine whether – like PBDEs – the HBCDs will be associated with adverse effects on human health, since, to date, no human health studies have been performed.
The few animal studies available show that HBCDs may have similar traits as their PBDE cousins. They may be endocrine disruptors and affect thyroid regulation by disrupting the mechanism by which thyroid hormones are transported in the body (Hamers et al. 2006; van der Ven et al. 2006).
Concern about these widely used brominated flame retardants is growing as more and more studies show increasing environmental and human exposures. For instance, the U.S. Environmental Protection Agency recently released details of its proposed plan to manage health and environmental risks associated with the HBCDs.
ResourcesChevrier, J, KG Harley, A Bradman, Hamers, T, JH Kamstra, E Sonneveld, AJ Murk, MHA Kester, PL Andersson, J Legler, A Brouwer. 2006. In vitro profiling of the endocrine disrupting potency of brominated flame retardants. Toxicological Science 92:157-173. HBCDs Action Plan. U.S. Environmental Protection Agency. Viewed February 12, 2011. Herbstman, JB, A Sjödin, M Kurzon, SA Lederman, RS Jones, V Rauh, LL Needham, D Tang, M Niedzwiecki, RY Wang and F Perera. 2010. Prenatal exposure to PBDEs and neurodevelopment. Environmental Health Perspectives 118:712–719. PBDEs. Agency for Toxic Substances and Disease Registry. Turyk, ME, VW Persky, P Imm, L Knobeloch, R Chatterton Jr. and HA Anderson. 2008. Hormone disruption by PBDEs in adult male sport fish consumers. Environmental Health Perspectives 116:1635–1641. van der Ven, LTM, A Verhoef, T van de Kuil, W Slob, PEG Leonards, TJ Visser, T Hamers, M Herlin, H Håkansson, H Olausson, AH Piersma, JG Vos. 2006. A 28-day oral dose toxicity study enhanced to detect endocrine effects of hexabromocyclododecane (HBCD) in Wistar rats. Toxicogical Science 94:281-292. |
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Flame retardants
