CORRESPONDENCE/REBUTTAL pubs.acs.org/est
Reply to Comment on “High Levels of Bisphenol A in Paper Currencies from Several Countries, and Implications for Dermal Exposure”
W
e appreciate the opportunity to respond to the comment of John E. Heinze1 on our recently published article2 that reported ubiquitous occurrence of high levels of bisphenol A (BPA) in paper currencies and concomitant dermal exposure through handling of currencies. The major intent of our publication2 was to report the widespread occurrence of BPA in paper currencies at concentrations on the order of several micrograms per gram (“partsper-million” level); this is important because the sources of human exposure to BPA are still not well characterized. The 2010 Joint Food and Agriculture Organization (FAO) and World Health Organization (WHO) expert meeting 3 identified that human exposure to BPA from nonfood sources is not wellknown. Evaluation of the sources of human exposure is essential if we are to develop strategies to mitigate exposures. In our study, we found that the mean concentrations of BPA in U.S. dollar bills (as an example) were several fold higher than the concentrations reported for house dust4 and foodstuffs (including canned foods; as shown in ref 3) from the U.S. This is a significant finding because prior to this study it was not known whether paper currencies contained BPA at concentrations greater than those found in house dust and foodstuffs. Heinze claims that our citation of the 2010 FAO/WHO report3 does not support our statement on health effects of BPA at low exposure doses. One of the major conclusions of the FAO/WHO expert meeting (see ref 3) on BPA was “some emerging new end-points (sex-specific neurodevelopment, anxiety, preneoplastic changes in mammary glands and prostate in rats, impaired sperm parameters) in a few studies show associations at lower levels”. Our intent was to convey the information that there are studies reporting adverse effects of BPA at low exposure doses (tens to hundreds of nanograms per kilogram body weight per day), and therefore the exposure levels measured from paper currencies should not be ignored. In fact, there are studies that show effects of BPA at doses below the current reference dose of 50 μg/kg bw/day (for reviews see refs 5 7). Nevertheless, considerable controversies surround the issue of low dose exposures and the reference dose. We believe that exposure to BPA from currencies can augment the total daily exposures; several such sources of BPA exposures still remain to be characterized. Heinze calculated the margin of exposure (MOE) by comparing the reference dose and the dermal intake from currencies, but ignored to indicate that the intake from currencies only represents “dermal pathway” and does not take into account of “inhalation pathway”. Because BPA is available as a powdery film on the surface of paper currencies, inhalation exposure can be significant. As indicated in our paper,2 our exposure assessment is limited to dermal uptake and does not include inhalation from handling of currencies (we did not analyze BPA released into air while handling paper currencies and therefore we did not report inhalation exposures). Furthermore, our exposure assessment involved several assumptions and uncertainties (which is intrinsic in all exposure and risk assessments). Overall, our r 2011 American Chemical Society
exposure assessment is an underestimate of the total exposure from currencies. The MOE of 140 thousand estimated by Heinze is an overestimate and his statement on health risk of BPA from currencies is premature and inconclusive. The 2010 FAO/WHO report concluded as “establishing a safe exposure level for BPA continues to be hampered by a lack of data from experimental animal studies that are suitable for risk assessment”. Furthermore, (contrary to what Heinze had indicated on his comment) we included a dermal permeation factor of 0.27 in our exposure assessment (absorption fraction: 27%, as we described clearly in our paper) and our exposure doses depict the lower dermal uptake rates, because only a fraction of BPA deposited on skin enters the blood circulation. Human exposure to BPA is a contentious public health issue and considerable controversies surround the issue of reference dose and low dose toxicity.5 7 The 2010 FAO/WHO report concluded that “...given the uncertainties, these findings should drive the direction of future research with the objective of reducing this uncertainty”. Our study provides valuable data for reducing one of the uncertainties in BPA exposure assessments. Chunyang Liao and Kurunthachalam Kannan* Wadsworth Center, New York State Department of Health, and Department of Environmental Health Sciences, School of Public Health, State University of New York at Albany, Empire State Plaza, P.O. Box 509, Albany, New York 12201-0509, United States
’ AUTHOR INFORMATION Corresponding Author
*Phone: 1-518-474-0015; fax: 1-518-473-2895; e-mail: kkannan@ wadsworth.org.
’ REFERENCES (1) Heinze, J. Comment on “high levels of bisphenol A in paper currencies from several countries, and implications for dermal exposure”. Environ. Sci. Technol. 2011, 45, DOI: dx.doi.org/10.1021/es203169y. (2) Liao, C.; Kannan, K. High levels of bisphenol A in paper currencies for several countries, and implications for dermal exposures. Environ. Sci. Technol. 2011, 45, 6761–6768. (3) FAO/WHO. Joint FAO/WHO Expert Meeting to Review Toxicological and Health Aspects of Bisphenol A. 2010. http://www. who.int/foodsafety/chem/chemicals/BPA_Summary2010.pdf (accessed September 20, 2011). (4) Loganathan, S. N.; Kannan, K. Occurrence of bisphenol A in indoor dust from two locations in the eastern United States and implications for human exposures. Arch. Environ. Contam. Toxicol. 2011, 61, 68–73. (5) Vandenberg, L. N.; Maffini, M. V.; Sonnenschein, C.; Rubin, B. S.; Soto, A. M. Bisphenol A and the great divide: A review of controversies in the field of endocrine disruption. Endocr. Rev. 2009, 30, 75–95. Published: September 28, 2011 9465
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Environmental Science & Technology
CORRESPONDENCE/REBUTTAL
(6) vom Saal, F. S.; Hughes, C. An extensive new literature concerning low-dose effects of bisphenol A shows the need for a new risk assessment. Environ. Health Perspect. 2005, 113, 926–933. (7) Goodman, J. E.; Witorsch, R. J.; McConnell, E. E.; Sipes, I. G.; Slayton, T. M.; Yu, C. J.; Franz, A. M.; Rhomberg, L. R. Weight-ofevidence evaluation of reproductive and developmental effects of low doses of bisphenol A. Crit. Rev. Toxicol. 2009, 39, 1–75.
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