Appendix C:  Additional evidence of highly concentrated exposures of breastfed infants to PBDEs, and that toxin’s effect of reducing testosterone levels:

C.1:  Extremes of exposure of breastfed infants:

A study by a team of seven scientists estimated PBDE intake from food to be 307 ng/kg/day for nursing infants compared with 0.9 ng/kg/day in adult females. (Schecter et al., Polybrominated Diphenyl Ether (PBDE) Levels in an Expanded Market Basket Survey of U.S. Food and Estimated PBDE Dietary Intake by Age and Sex   Environ Health Perspect. 2006 October; 114(10): 1515–1520. Published online 2006 July 13. doi: 10.1289/ehp.9121, PMCID: PMC1626425) 

The EPA quotes estimates from two other studies that were almost that extreme. (p. 5-55 of EPA:  An exposure assessment of polybrominated diphenyl ethers. National Center for Environmental Assessment, Washington, DC; EPA/600/R-08/086F. online at http://www.epa.gov/ncea  or directly at  http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=210404 )  

 

In the only study quoted by the EPA making such a comparison, based on measurements of 244 children, the average total concentration of PBDEs in breastfed children at age four was still nearly three times as high as in formula-fed children. (Near end of Section 5.6.2 ("Impacts to Infants from Consumption of Breast Milk"), p. 5-79, of An exposure assessment of polybrominated diphenyl ethers. National Center for Environmental Assessment, Washington, DC; EPA/600/R-08/086F. online at http://www.epa.gov/ncea  or directly at  http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=210404

 

According to a study, “combustion sources are probably more important PBDE contributors to outdoor air levels and have more influence on the food chain, which is one of the major routes for human and wildlife PBDE exposure.” (1)  The dominant effect of combustion sources of PBDEs in outdoor air is probably the main reason why urban air has been found to have almost ten times the concentration of PBDEs as rural air, as reported by the U.S. Agency for Toxic Substances and Disease Registry. (Section 4.1 of ATDSR document on PBDEs at http://www.atsdr.cdc.gov/toxprofiles/tp68-c4.pdf)

   

 

A 2015 Australian study stated that, despite declines of new emissions of PBDEs (mainly resulting from major reductions in use that had become effective in 2004), “the PBDE exposure of fetuses and breast-fed infants (the most sensitive groups) has remained rather constant. Gyalpo et al., Insights into PBDE Uptake, Body Burden, and Elimination Gained from Australian Age-Concentration Trends Observed Shortly after Peak Exposure, Environ Health Perspect, 2015 Oct;123(10):978-84. doi: 10.1289/ehp.1408960. Epub 2015 Mar 13, http://www.ncbi.nlm.nih.gov/pubmed/25768049   Another EPA report states that research found that “Infant exposures (to PBDEs) were dominated by breast milk ingestion.”National Center for Environmental Assessment, Office of Research and Development, U.S. EPA,  An Exposure Assessment of Polybrominated Diphenyl Ethers,  EPA/600/R-08/086F May 2010, p. 5-56  One study team calculated that 91% of a typical U.S. breastfed infant’s total exposure to PBDEs was from breast milk. Johnson-Restrepo, An assessment of sources and pathways of human exposure to polybrominated diphenyl ethers in the United States, Chemosphere, 2009 Jul;76(4):542-8. doi: 10.1016/j.chemosphere.2009.02.068. Epub 2009 Apr 5.  at http://www.ncbi.nlm.nih.gov/pubmed/19349061

 

C.2:  Testosterone-reducing effects of PBDEs:

A 2013 study (Johnson et al.) found a 9.4% decrease in testosterone levels with each interquartile increase in deca-BDE concentration in house dust, with a fairly high level of statistical significance (p-value - .02).Johnson et al., Associations between brominated flame retardants in house dust and hormone levels in men, Sci Total Environ. 2013 Feb 15; Table 3, PMCID: PMC3572297, 445-446: 177–184.at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3572297/    This has special importance in that deca-BDEs were still in wide use in consumer electronic products and home furnishings until 2015, and will long be part of human environments and exposures. Putting the interquartile differences into other words, the above means that the rather common difference in household PBDE dust levels between the bottom quarter and the top quarter of this kind of population would be associated with a 28% (3 times 9.4%) reduction in testosterone levels. Remember that testosterone is important to development of the brain (see Section 4.a)

 

Although effects related to differences between quartiles of PBDE exposure are significant, effects that could result from the more extreme exposures of those in the top few percent should be of far greater concern. In the above study of 38 households, one of those households (constituting over 2% of the population studied) had decaBDE exposure that was 27 times the exposure at the 25th percentile. (see Table 1 in that study)  That extreme exposure in the top 2% of this study group was completely in line with other studies -- see the Schecter et al. and Chinese studies above. It is entirely likely that a significant percentage of exposed children in the Johnson et al. study would have had far greater reductions of the neurodevelopmentally-important testosterone than the 28% reduction associated with top-quartile-versus-bottom-quartile levels of PBDEs.

 

Notes:_________________

1)  Wang et al., Emission estimation and congener-specific characterization of polybrominated diphenyl ethers from various stationary and mobile sources, Environmental Pollution, Vol. 158, issue 10, Oct. 2010, pp. 3108-3115 at http://www.sciencedirect.com/science/article/pii/S0269749110002769 ; also  Wang et al., Polybrominated diphenyl ethers in various atmospheric environments of Taiwan: Their levels, source identification and influence of combustion sources, Chemosphere, Volume 84, Issue 7, Aug. 2011  at http://www.sciencedirect.com/science/article/pii/S0045653511006515