Environ. Sci. Technol. 2008, 42, 9455–9456
Response to Comment on “Alternate and New Brominated Flame Retardants Detected in U.S. House Dust” We thank Marcia Hardy and her coauthors for their letter (1) regarding our paper entitled “Alternate and New Brominated Flame Retardants Detected in U.S. House Dust”, published recently in Environmental Science & Technology (2). The intent of our paper was to report on the discovery and measurement of alternate (relative to PBDEs), and recently introduced brominated flame retardants (BFRs) in U.S. house dust, and not to evaluate health risks. In our paper we stated that “...children living in homes where the dust levels of these BFRs are >90th percentile may be receiving significant exposures.” Because concentrations of these compounds are log-normally distributed in house dust, some homes contain high levels of these BFR compounds, and thus children living in these homes may be receiving elevated exposures relative to the median population. Exposure does not necessarily translate to specific health risks, and we have not made this claim in our paper. However, in their comments Hardy et al. have raised several points, which we feel are important to address. First, a major point of our paper was to highlight the effort needed to determine the identity of unknown but significant brominated peaks in the GC/MS chromatograms from our dust samples. Through our effort we were able to identify the following two new brominated flame retardant chemicals: 2-ethylhexyl 2,3,4,5-tetrabromobenzoate (TBB) and bis-(2ethylhexyl)-tetrabromophthalate (TBPH). Following identification of these compounds, we were able to determine that TBPH is used alone as a flame retardant and is a high production volume (HPV) chemical. Also of interest to note is that these two chemicals are also found in a new flame retardant mixture known as Firemaster 550 (FM550). FM 550 is a PentaBDE replacement manufactured by Great Lakes Chemical, a Chemtura company. The identity of the brominated component(s) in this mixture is listed on their Material Safety Data Sheet (MSDS) as a trade secret, which severely complicates the task of both environmental scientists and consumers in evaluating the risk posed by their inclusion in consumer products. While some toxicological data are available on the USEPA’s High Production Volume Web site (http://www.epa.gov/ hpvis/) for TBPH (CAS 26040-51-7), e.g., a subchronic rodent study, no developmental studies are reported (3). Furthermore, these studies have not been published in the peerreviewed open literature. As no reference dose (RfD) values are available for TBPH, Hardy et al. used RfD values for diethylhexylphthalate (DEHP) as a surrogate chemical. However, the addition of four bromine atoms on TBPH will likely affect its physiological behavior, adding more uncertainty to the risk analysis. In addition, we found no data on the toxicity, bioaccumulation potential, or degradation potential of TBB. And a recent report by the U.S. Consumer Product Safety Commission also declared that insufficient toxicity data, physico-chemical data, and exposure data are available for the brominated components of FM 550 to assess hazard to consumers (4). Taken together, the use of unpublished, incomplete data for the risk analysis lacks the transparency that should be available to assess risk to populations routinely exposed to these compounds. 10.1021/es8026192 CCC: $40.75
Published on Web 11/14/2008
2008 American Chemical Society
Second, Hardy et al. appear to be addressing risk from the standpoint of exposure to each individual compound. However, these alternative BFRs, as well as PBDEs, PCBs, and phthalates, are all present in mixtures in indoor dust and no information is currently available on the risks due to exposure to these mixtures. Will they result in interactive effects that are additive or synergistic? This has not been evaluated, thus comparing exposures to single compounds, for which surrogate reference doses (RfDs) have been assigned, to exposure to multiple BFR compounds, without consideration of uncertainty, may not be adequate to fully evaluate risk. In addition, the analysis of Hardy et al. only estimated exposure to dust via ingestion, ignoring additional exposure pathways that include diet, inhalation, and dermal contact, which also may be important. Lastly, Hardy et al. also state that the National Academy of Sciences (NAS) calculated a RfD for HBCD of 200,000 ng/ kg-day [NAS, 2000]. However, this RfD value for HBCD was calculated using data from an unpublished subchronic study done in rats by Zeller and Kirsch (1970), almost 40 years ago. The NAS concluded that confidence in this RfD is low, because of a lack of other subchronic and chronic studies. We believe that published developmental exposure studies are needed before an accurate RfD value can be calculated. Also of interest to note is that HBCD has been increasing in concentration in several environmental matrices (5, 6) and it is feasible that human exposure to HBCD, and other new types of alternate flame retardants, may also increase in the future, similar to what has been observed for PBDEs (7, 8).
Literature Cited (1) Hardy, M.; Biesemeir, J.; Banasik, M.; Stedeford, T. Brominated flame retardants in house dust: Detection does not equate to risk. Environ. Sci. Technol. 2008, 42, 9453–9454. (2) Stapleton, H. M.; Allen, J. G.; Kelly, S. M.; Konstantinov, A.; Klosterhaus, S.; Watkins, D.; McClean, M. D.; Webster, T. F. Alternate and new brominated flame retardants detected in U.S. house dust. Environ. Sci. Technol. 2008, 42 (18), 6910– 6916. (3) Health & Environmental Horizons, L. Test Plan for Phthalic Acid Tetrabromo Bis 2-Ethylhexyl Ester (CAS#26040-51-7); Arlington, VA, July 1, 2004; p 36. (4) Babich, M. A. CPSC Staff Preliminary Risk Assessment of Flame Retardant (FR) Chemicals in Upholstered Furniture Foam; U.S. Consumer Product Safety Commission: Bethesda, MD 20814, 2006; p 129. (5) Stapleton, H. M.; Dodder, N. G.; Kucklick, J. R.; Reddy, C. M.; Schantz, M. M.; Becker, P. R.; Gulland, F.; Porter, B. J.; Wise, S. A. Determination of HBCD, PBDEs and MeO-BDEs in California sea lions (Zalophus californianus) stranded between 1993 and 2003. Mar. Pollut. Bull. 2006, 52 (5), 522–531. (6) Law, R. J.; Bersuder, P.; Allchin, C. R.; Barry, J. Levels of the flame retardants hexabromocyclododecane and tetrabromobisphenol A in the blubber of harbor porpoises (Phocoena phocoena) stranded or bycaught in the UK, with evidence for an increase in HBCD concentrations in recent years. Environ. Sci. Technol. 2006, 40 (7), 2177–2183. (7) Hites, R. A. Polybrominated diphenyl ethers in the environment and in people: A meta-analysis of concentrations. Environ. Sci. Technol. 2004, 38 (4), 945–956. (8) Sjodin, A.; Jones, R. S.; Focant, J. F.; Lapeza, C.; Wang, R. Y.; McGahee, E. E.; Zhang, Y. L.; Turner, W. E.; Slazyk, B.; Needham, L. L.; Patterson, D. G. Retrospective time-trend study of polybrominated diphenyl ether and polybrominated and polychlorinated biphenyl levels in human serum from the United States. Environ. Health Perspect. 2004, 112 (6), 654– 658. VOL. 42, NO. 24, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
9455
Heather M. Stapleton and Shannon M. Kelly
Deborah J. Watkins, Wendy J. Heiger-Bernays, Michael D. McClean, and Thomas F. Webster
Duke University, Nicholas School of the Environment & Earth Sciences, Durham, North Carolina
Boston University School of Public Health, Department of Environmental Health, Boston, Massachusetts
Joseph G. Allen Boston University School of Public Health, Department of Environmental Health, Boston, Massachusetts, and Environmental Health & Engineering, Inc., Needham, Massachusetts
9456
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 42, NO. 24, 2008
Alex Konstantinov Wellington Laboratories, Guelph, Ontario, Canada
Susan Klosterhaus San Francisco Estuary Institute, Oakland, California ES8026192
