Healthy Milk, Healthy Baby
Chemical Pollution and Mother's Milk
BACK TO CHEMICAL OVERVIEW
Polybrominated diphenyl ethers (PBDEs) are a class of widely used flame retardants. The chemical structure of the PBDEs closely resembles the structure of PCBs, dioxins and furans. Rather than containing chlorine, however, these chemicals contain bromine. PBDEs are present in commercial product materials at up to 30 percent of overall material weight, and they have become the second largest class of additives used by the plastics industry.1
Like PCBs, PBDEs accumulate in fat and resist degradation in the environment. As additive flame retardants, PBDEs are not chemically bound to consumer products, but merely dissolved, so they can leach out and evaporate into the environment over time. These characteristics have led to rapid bioaccumulation of PBDEs in human and animal fat tissue, and caused widespread concern about their potential impact on human and ecological health.2
PBDEs are most commonly produced and used in three different classes of the 209 possible PBDE molecules, or "congeners." Each class has a different number and formation of the individual congeners. The three major brominated flame retardant classes are: penta-, octa- and deca-BDEs. Penta-BDEs are most commonly added to polyurethane foam used for furniture cushions. Octa-BDEs are additives used in the plastic housings for televisions, computers, telephones, automotive parts and other electronics. Deca-BDEs are also additives used in the high-impact plastic housings for electronic equipment, as well in upholstery fabric, plastic furniture and plastic toys. In 1999, the United States used 8,000, 1,400 and 25,000 metric tons of penta-, octa- and deca-BDEs, respectively, which corresponds with 98 percent, 36 percent and 44 percent of global production.3
Health Effects of PBDEs
PBDEs are structurally similar to thyroid hormones and may block the transport of thyroid hormones throughout the body. Thyroid hormones are responsible for regulating many essential metabolic functions, and are extremely important in promoting normal brain development in infants.4 In rodents, PBDEs decrease thyroid-hormone levels in both mothers and developing fetuses and babies, alter thyroid-hormone regulation and reduce birth weight of offspring. This disruption of thyroid-hormone regulation has frequently been associated with permanent behavior problems and brain damage.5 Rodents exposed to PBDEs, when compared to unexposed rodents, were found to become hyperactive, show decreased control of their muscles and have slower or abnormal responses to stressful or sudden changes in situation. They also became less responsive to situations that should have caused fearful responses.6
Deca-BDE is the only class of PBDEs to be studied for cancer-causing properties. The resulting data gap is particularly unfortunate because deca-BDE is the most poorly absorbed in the intestine of the three common PBDE congeners. So the animals were given very large doses of deca-BDE, making the relevance of the study to humans somewhat uncertain. These animals developed liver and pancreatic tumors at high exposure levels. Cancerous tumors of the thyroid gland were also found to increase significantly.7 This evidence is preliminary, as few cancer studies have been conducted, and carcinogenic effects of penta- and octa-BDE still need to be assessed.
PBDEs in the Body
PBDEs were first identified in living organisms in 1981, when they were found in fish samples from western Sweden.8 Since then, they have been found in birds, fish, shellfish, amphibians, marine mammals, sewage sludge, sediments, air samples, meats, dairy products and even vegetables in numerous North American and European locations, as well as in Japan.9 Most alarming, however, has been their discovery in human blood, fatty tissue, umbilical cord blood and breast milk in every region where scientists have conducted studies. Furthermore, in many areas, concentrations have been increasing exponentially.10
The widespread occurrence of high PBDE concentrations indicates that PBDEs are probably entering the environment during various phases of product manufacturing, use and disposal, rather than just at limited sites of production.11 Human exposure to PBDEs probably occurs through workplace exposure during production of PBDEs or PBDE-containing products, by exposure in the home and as a result of eating PBDE-contaminated fish.
Research has shown that PBDEs can evaporate into the indoor environment from electronics and other PBDE-containing household or office products. In addition, materials containing PBDEs often degrade with age and use, releasing PBDEs as they break down. For example, when polyurethane foam ages it becomes brittle and crumbles into tiny fragments, particularly when exposed to sunlight. This foam dust can get into the air, soil and water, and into the bodies of humans living with aging furniture.12 At present, it is still unclear to scientists which of the possible exposure pathways for PBDEs play the largest role in contributing to the levels found in breast milk.
Two studies have demonstrated occupational exposure of Swedish workers to PBDEs by comparing PBDE levels in office workers, computer technicians, workers at an electronics-dismantling plant and hospital janitorial staff. Together, the studies show a clear gradient from the least exposed janitorial staff up to the most exposed electronics plant workers. The researchers were also able to find a positive relationship between the amount of time the technicians worked in front of computers and the PBDE contamination levels in their blood.13
Studies investigating PBDE exposure through the diet have found that the foods highest in PBDE concentrations are fatty fish and shellfish. A strong positive relationship between PBDE levels in women's breast milk and the amount of fish in their diet was observed in a 2002 study from Japan.14 An Italian study of PBDE levels in all types of foods estimated that fish and shellfish account for about one-third of total intake through the diet.15
Controlling Exposure: Bans and Restrictions
As of August 2004, the European Union has banned the use of penta- and octa-BDEs in all products, following earlier individual phaseouts and restrictions in Sweden, Denmark, Germany and the Netherlands. The EU is also phasingout the use of deca-BDE in electronics by July of 2006.16
In the United States, no federal regulatory action has been taken to ban or restrict PBDEs. The U.S. EPA reached a voluntary agreement with the sole U.S. manufacturer of penta- and octa-BDE under which that company ceased production of these chemicals at the end of 2004. California was the first state to phase out the penta- and octa-BDEs. California Assembly Bill 302, banned production, processing and distribution of products containing more than 10 percent penta- or octa-BDEs by January of 2008. The bill exempts deca-BDE and does not require labeling of PBDE-containing products.17 More recently, the state of Maine has banned all PBDEs. The ban on penta- and octa-BDE is effective as of January 2006, whereas deca-BDE will be banned by January 2008 if safer alternatives can be found.
Japan has voluntarily restricted the use and production of penta-BDEs, while octa- and deca-BDEs are still in use. The Canadian government is currently researching the impact of PBDEs, but has not banned or restricted any classes of PBDEs.18
Some private companies, such as the Swedish home furnishing company IKEA, have voluntarily stopped producing products that contain PBDEs and are putting pressure on product distributors to start producing alternatives. The following companies report that they have stopped using, or are phasingout, PBDEs: Apple, Dell, Ericsson, HP, IBM, Intel, Motorola, Panasonic, Phillips and Sony.19
Benchmarks and Exposure Limits for PBDEs
Because PBDE contamination is a relatively newly understood phenomenon, no benchmarks or "safe" levels have been set for human exposure.
Breast Milk Monitoring Studies Looking at PBDEs
Very few breast milk monitoring studies have measured PBDEs. Extensive data from Sweden, and some limited data from Germany, Canada and Japan have been collected, as well as some limited U.S. data from California, Texas, Indiana, Colorado and New York State.
The examples presented here are divided into three types:
- Time trend example -- a Swedish study that has looked at average levels of PBDEs in breast milk over a number of years
- Differences in average levels among different countries and different parts of the United States
- Occupational exposure to PBDEs
Time Trend Example
Data from Sweden sounded the first alarm about the potential for breast milk contamination from PBDEs. In the Swedish study, archived samples collected between 1972 and 1997 were analyzed for the presence of PBDEs to get an overall summed total of PBDEs in milk. An average for each time period was calculated and is shown in Figure 1.20
The data from Sweden show a drastic increase in the quantity of PBDEs detected in women's breast milk prior to 1997, with concentrations doubling every five years between 1972 and 1997.21 Sweden's voluntary phaseout of PBDEs by companies and branches of the government began as early as 1990, and the Swedish government strongly encouraged the European Union to ban PBDEs outright.22 A striking response to Sweden's voluntary PBDE controls can be seen after 1997. Total PBDE levels in Swedish women's breast milk fell about 30 percent between 1997 and 2000, from a high of about 4 ng/g of milk fat, to 2.79 ng/g fat.23 Sweden is the only nation with a comprehensive breast milk monitoring program, so it has been difficult to track PBDE concentration trends elsewhere. However, in regions where bans and restrictions have not been established, available studies are showing that PBDE concentrations in breast milk have risen far past Sweden's 1997 peak of 4 ng/g milk fat.
International and Regional Comparisons
The highest recorded PBDE levels in humans to date have been in the United States. A 2002 study of PBDEs in San Francisco Bay Area women's breast fat reported an average of 86 ng/g fat,24 which is 21.5 times higher than Sweden's 1997 peak. Studies of PBDEs in maternal blood and milk in Texas and Indiana from 2001 and 2002 reported levels similar to those found in the San Francisco Bay Area. The mean concentration reported in Texas was 74 ng/g fat, and maximum concentrations in the two studies were 419 and 580 ng/g fat, respectively.25 Average PBDE levels in Japanese women's breast milk are comparable with those found in Sweden and other parts of Europe, and levels in Canada were recently found to be 25.4 ng/g fat,26 leaving the United States with average PBDE levels about 3 times higher than those found in Canada, and between ten and more than 100 times higher than those measured in Japan, Sweden and other parts of Europe.27 Figure 2 shows the differences in the median levels of the three most abundant PBDE congeners found in the United States and those found in Canada and Europe.28 Medians were used for this figure, as means were not available for all of these studies. When means are used, the concentration differences are even more pronounced, due to the extremely high maximum concentrations found in North America.
Occupational Exposure to PBDEs
Though levels of occupational exposure to PBDEs have not been assessed through breast milk monitoring studies, two Swedish studies of PBDE concentrations in four groups of workers' blood show a trend indicating that PBDE concentrations may be related to the amount of time workers spend in close contact with PBDE-containing electronic equipment.29 Figure 3 shows that workers in an electronics dismantling plant and computer technicians had higher PBDE concentrations than office workers and hospital cleaners, and that they also had higher concentrations of BDE-209 (deca-BDE) in their blood.
The appearance of increasing levels of deca-BDE in workers with greater exposure to electronic equipment is particularly notable, since deca-BDE is used in far greater volumes than penta- or octa-BDEs. Deca-BDE has been considered to be less harmful than the other PBDE classes because studies have identified penta- and octa-BDEs in much higher concentrations in human and animal fat than deca-BDE, indicating higher rates of bioaccumulation.30 As a result, in places where PBDEs are regulated, penta- and octa-BDEs have been more stringently restricted or banned than deca-BDE.31 However, through studies such as these, researchers are now finding that deca-BDE is indeed absorbed into the body, though less easily than penta- or octa-BDEs. Other research suggests that deca- and octa-BDEs may also be breaking down in the environment to the more readily absorbed penta-BDEs.32 Further scientific inquiry is necessary to clarify these differences in occupational exposure and protect workers from PBDEs in the workplace.
It is important to note that no data regarding the health effects of children's exposure to PBDEs in breast milk have been published. However, enough is known to raise concerns. The trend toward higher levels in breast milk signals a need for immediate action to stop human exposures, before the levels rise higher and risk compromising the safety of children's first food.
Related Sites on the WebRead the article, "Polybrominated Diphenyl Ethers (PBDEs) in U.S. Mothers' Milk," published in the journal Environmental Health Perspectives.
A study by the Environmental Working Group found record high levels of PBDEs in breast milk from American mothers. Read the 2003 report.
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3. Madsen, T., S. Lee, T. Olle, "Growing Threats: Toxic Flame Retardants and Children's Health," Environment California Research and Policy Center (2003); Hale, R.C., M.J. La Guardia, E. Harvey, T.M. Mainor, "Potential role of fire retardant-treated polyurethane foam as a source of brominated diphenyl ethers to the US environment," Chemosphere vol. 46, no. 5 (2002): pp. 729-735.
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13. Jakobsson, K., K. Thuresson, L. Rylander, A. Sjodin, L. Hagmar, A. Bergman, "Exposure to polybrominated diphenyl ethers and tetrabrombisphenol A among computer technicians," Chemosphere vol. 46, no. 5 (2002) pp. 709-716; Sjodin, A,, L. Hagmar, E. Klasson-Wehler, K. Kronholm-Diab, E. Jakobsson, A. Bergman, "Flame Retardant Exposure: Polybrominated Diphenyl Ethers in Blood from Swedish Workers," Environmental Health Perspectives, vol 107, no 8 (August 1999): pp. 643-648.
14. Ohta S., D. Ishizuka, H. Nishimura, T. Nakao, O. Aozasa, Y. Shimidzu, F. Ochiai, T. Kida, M. Nishi, H. Miyata, "Comparison of polybrominated diphenyl ethers in fish, vegetables, and meats and levels in human milk of nursing women in Japan, " Chemosphere vol. 46, no. 5 (2002): pp. 689-696.
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16. European Union (EU), Directive of the European Parliament and of the Council on the restriction of the use of certain hazardous substances in electrical and electronic equipment. Document PE-CONS 3662/02, Brussels, 8 Nov. 2002. Official Journal C 127E, 29.5.2003: 510-515. http://europa.eu.int/
20. Meironyte, D., K. Noren, and A. Bergman, "Analysis of Polybrominated Diphenyl Ethers in Swedish Human Milk, A Time-related Trend study, 1972-1997," Journal of Toxicology and Environmental Health Part A vol. 58, no. 6 (1999): pp. 329-341; Noren, K. and D. Meironyte, "Certain Organochlorine and Organobromine Contaminants in Swedish Human Milk in Perspective of Past 20-30 Years," Chemosphere vol. 40, no. 9-11 (2000): pp. 1111-1123.
21. Meironyte, et al., "Analysis of polybrominated diphenyl ethers in Swedish human milk. A time-related trend study, 1972-1997," Journal of Toxicological Environmental Health Part A vol. 58, no. 6 (1999): pp. 329-341.
23. Darnerud, P.O., M. Aune, S. Atuma, W. Becker, R. Bjerselius, S. Cnattingius, A.. Glynn, "Time trend of polybrominated diphenyl ether (PBDE) levels in breast milk from Uppsala, Sweden, 1996-2001, Organohalogen Compounds 58 (2002): pp 233-236.
24. She, J., M. Petreas, J. Winkler, P. Visita, M. McKinney, D. Kopec, "PBDEs in the San Francisco Bay Area: measurements in harbor seal blubber and human breast adipose tissue," Chemosphere vol 46, no. 5 (2002): pp. 697-707.
25. Schecter A, M. Pavuk, O. Papke, J.J. Ryan, :L. Birnbaum, R. Rosen, "Polybrominated Diphenyl Ethers (PBDEs) in U.S. Mothers' Milk," Environmental Health Perspectives vol. 111, no. 14 (August 2003) pp. 1723-1729; Mazdai, A., N. G. Dodder, M.P. Abernathy, R.A. Hites, R.M. Bigsby, "Polybrominated Diphenyl Ethers in Maternal and Fetal Blood Samples," Environmental Health Perspectives, vol. 111, no. 9 (July 2003): pp. 1249-1252.
27. Ohta et al. "Comparison of polybrominated diphenyl ethers in fish, vegetables, and meats and levels in human milk of nursing women in Japan," Chemosphere vol. 46, no. 5 (2002): pp. 689-696; Schecter et al. "Polybrominated Diphenyl Ethers (PBDEs) in U.S. Mothers' Milk," Environmental Health Perspectives vol. 111, no. 14 (2003) pp. 1723-1729; Meironyte, M.G., A. Aronsson, G. Ekman-Ordeberg, A. Bergman, K. Noren, "Human prenatal and postnatal exposure to polybrominated diphenyl ethers, polychlorinated biphenyls, polychlorobiphenylols and pentachlorophenol," Environmental Health Perspectives vol. 111, no. 9 (July 2003): pp. 1235-1241; Betts, K.S,R"apidly rising PBDE levels in North America," Environmental Science and Technology vol. 36, no. 3 (2002): pp. 50A-52A.
28. Schecter et al., "Polybrominated Diphenyl Ethers (PBDEs) in U.S. Mothers' Milk," Environmental Health Perspectives vol. 111, no. 14 (2003) pp. 1723-1729; Meironyte et al., "Human prenatal and postnatal exposure to polybrominated diphenyl ethers, polychlorinated biphenyls, polychlorobiphenylols and pentachlorophenol," Environmental Health Perspectives vol. 111, no. 9, (2003): pp. 1235-1241; Ryan et al. "Recent Trends in Levels of Brominated Diphenyl Ethers (BDEs) in Human Milks from Canada," Organohalogen Compounds vol. 58 (2002) pp. 173-176; She et al., "PBDEs in the San Francisco Bay Area: measurements in harbor seal blubber and human breast adipose tissue," Chemosphere vol 46, no. 5 (2002): pp. 697-707.
29. Jakobsson et al., "Exposure to polybrominated diphenyl ethers and tetrabrombisphenol A among computer technicians," Chemosphere vol. 46, no. 5 (2002): pp. 709-716; Sjodin et al. "Flame Retardant Exposure: Polybrominated Diphenyl Ethers in Blood from Swedish Workers," Environmental Health Perspectives vol. 107, no. 8 (August 1999): pp. 643-648.
30. de Boer, J., P.G. Wester, A. van der Horst, P.E. Leonards, "Polybrominated diphenyl ethers in influents, suspended particulate matter, sediments, sewage treatment plant effluents and biota from the Netherlands," Environmental Pollution vol. 122, no. 1, (2003): pp. 63-74; Thomsen et al. "New Method for Determination of Halogenated Flame Retardants in Human Milk Using Solid-Phase Extraction," Journal of Analytical Toxicology vol. 26, no. 3 (2002): pp. 129-137; Bocio et al. "Polybrominated Diphenyl Ethers (PBDEs) in Foodstuffs: Human Exposure through the Diet," Journal of Agricultural and Food Chemistry vol. 51, no. 10 (2003) pp. 3191-3195.
32. Ikonomou, M.G., S. Rayne, R.F. Addison, "Exponential Increases of the Brominated Flame Retardants, Polybrominated Diphenyl Ethers, in the Canadian Arctic from 1981 to 2000," Environmental Science and Technology vol. 36, no. 9 (2002): pp. 1886-1892; Jakobsson et al., "Exposure to polybrominated diphenyl ethers and tetrabrombisphenol A among computer technicians," Chemosphere 46 (2002): pp. 709-716; McDonald, T. A. "A perspective on the potential health risks of PBDEs," Chemosphere vol. 46, no. 5 (2002): pp. 745-755.
last revised 3.25.05