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mean ± SD) (Table 4). The amount of Cr hypothesized to have been in water from wells G and H, 240 Wgl, and the mean con- centration of Cr in the hair ofWoburn resi- dents who had access to this water, -2.8 pg/g, are consistent with the relationship between Cr in drinking water and Cr in hair reported by Rosas et al. (24). However, as we have already noted, the concentration of Cr in the hair ofWoburn residents who did not have access to the well water (and thus, presumably, were exposed to substantially less Cr via drinking water) was also on aver- age -2.8 pg/g. Furthermore, the concentra- tions of Cr in hair did not change as a finc- tion of access. Therefore, it appears that access to water from wells G and H cannot explain Cr levels measured in the hair of Woburn residents.

Another possible explanation for our negative findings is that our analysis lacked adequate temporal resolution. If the As and Cr concentrations to which a hair sample donor were exposed were temporally vari- able, a more powerful analysis could be achieved by measuring the axial distribution of As and Cr along individual hair strands. This approach has in fact been used by forensic scientists to distinguish chronic and acute As and Cr exposures (38-40). By contrast, our analysis of whole, unsegment- ed hair strands does not detect concentra- tion spikes along the strand.

There are several other sources of uncer- tainty associated with our methods that could also bear upon our results. The period of hair growth was overestimated for 14 of the samples grown between 1964 and 1979 because the month that the sample was cut was not known. The water distribution model used to estimate access is not entirely free oferror. In addition, As and Cr concen- trations in the hair samples could have changed during storage. While it is impor- tant to acknowledge that these (and possibly other) sources of uncertainty were inherent in our methods, we do not expect that greater knowledge of any of these uncertain- ties would significantly alter our findings.

Although we did not find evidence of increased As and Cr accumulation in the hair ofWoburn residents who had access to water from wells G and H, we did observe that As concentrations in the hair samples have changed over time. The plot of As concentrations in hair samples versus the year that the samples were cut (Fig. 3A) shows that concentrations ofAs in hair have decreased over the last half century. The concentrations of As in hair averaged over the periods 1938-1963, 1964-1979, and 1982-1994 [expressed as geometric means (GSD)] were 0.21 (3.0) pg/g (n = 26), 0.15 (2.4) pg/g (n = 36), and 0.06 (2.6) plg/g (n


= 20), respectively (Table 2). The reasons for this trend are not known; however, replacement of As-based pesticides by syn- thetic organic chemicals has undoubtedly reduced the amount of As to which people are exposed through diet and use of phar- maceutical products, and improvements in air pollution control technology have reduced the amount ofAs emitted into the atmosphere. Also, once the major producers of As-laden wastes ceased operating in Woburn (around 1930), natural attenua- tion processes, such as stabilization of As- containing particles by vegetation and deposition and burial in pond and lake sed- iments, may have acted to substantially reduce the amounts ofavailable As to which residents ofWoburn are exposed.


1. Massachusetts State Board of Health. Second Annual Report. Boston, MA:Department of Public Health, 1871. 2. Massachusetts State Board of Health. Fifth Annual Report. Boston, MA:Department of Public Health, 1874. 3. Massachusetts State Board of Health. Sixth Annual Report. Boston, MA:Department of Public Health, 1875. 4. Tarr JA. History of pollution in Woburn, Massachusetts. In: Wells G&H Site Remedial Investigation Report Part 1, Woburn, Massachusetts, Vol 2. Boxborough, MA: GeoTrans, Inc., 1987. 5. Durant JL, Zemach JJ, Hemond HF. The histo- ry ofleather industry waste contamination in the Aberjona watershed: a mass balance approach. J Boston Soc Civ Eng 5:41-65 (1990). 6. Department of Environmental Protection. List of Confirmed Disposal Sites and Locations to Be Investigated. Boston, MA:Department of Environmental Protection, 1993. 7. Aurilio A, Durant JL, Hemond HF. Sources and distribution ofarsenic contamination in the Aberjona watershed, eastern Massachusetts. Water Air Soil Pollut 81:265-282 (1995). 8. Davis A, Sellstone C, Clough S, Barrick R, Yare B. Bioaccumulation of arsenic, chromium and lead in fish: constraints imposed by sedimentary geochemistry. Appl Geochem 11:409-423 (1996). 9. Bowen HJM. Environmental Chemistry of the Elements. New York:Academic Press, 1979. 10. Shacklette HT, Boerngen JG. Element Concentrations in Soils and Other Surficial Materials of the Conterminous United States. USGS Professional Paper 1270. Alexandria, VA:U.S. Geological Survey, 1992. 11. Knox M. The distribution and depositional his- tory of metals in surface sediments of the Aberjona watershed [M.S. Thesis]. Massachusetts Institute ofTechnology, Cambridge, MA, 1991. 12. Spliethoff HM, Hemond HF. History of toxic metal discharge to surface waters of the Aberjona watershed. Environ Sci Technol 30:121-128 (1996). 13. Durant JL, Chen J, Hemond HF, Thilly WG. Elevated incidence of childhood leukemia in Woburn, Massachusetts: NIEHS superfund

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Environ Health Perspect 103(suppl 6):93-98 (1995). 14. Murphy PJ. Water Distribution in Woburn, MA; Massachusetts Department of Environmental Quality Engineering, Office of Research and Standards, Pub No 86-1. Amherst, MA:The Environmental Institute, University of Massachusetts, 1986. 15. Myette CF, Olimpio JC, Johnson DG. Area of Influence and Zone of Contribution to Superfund-Site Wells G and H, Woburn Massachusetts. USGS Water-Resources Investigation Report 87-4100. Boston, MA:U.S. Geological Survey, 1987. 16. Stoeppler M, Vahter M. Arsenic. In: Techniques and Instrumentation in Analytical Chemistry: Trace Element Analysis in Biological Specimens, Vol 15 (Herber RFM, Stoeppler M, eds). Amsterdam:Elsevier, 1994;291-320. 17. Liebscher K, Smith H. Essential and nonessen- tial trace elements. A method of determining whether an element is essential and nonessential in human tissue. Arch Environ Health 17:881-890 (1968). 18. Randall J, Gibson R. Hair chromium as an index of chromium exposure of tannery work- ers. Br J Ind Med 46:171-175 (1989). 19. Pankhurst CA, Pate BD. Trace elements in hair. Rev Anal Chem 4:111-235 (1979). 20. Hambidge MK, Franklin ML, Jacobs MA. Hair chromium concentrations: effects of sample washing and external environment. Am J Clin Nutr 25:384-389 (1972). 21. Valentine JL, Kang HK, Spivey G. Arsenic lev- els in human blood, urine, and hair in response to exposure via drinking water. Environ Res 20:24-32 (1978). 22. Zhang C, Wang G, Xiao B. Research on the physicochemical properties of hair in endemic arsenism areas. J Zhong Hua Prevent Med 26:19-22 (1992). 23. Khorvat A. Arsenic content in the body of peo- ple residing in a territory with increased arsenic levels. Gig Sanit 6:62-65 (1981). 24. Rosas I, Belmont R, Baez A, Villalobos-Pietrini R. Some aspects of the environmental exposure to chromium residues in Mexico. Water Air Soil Pollut 48:463-475 (1989). 25. International Atomic Energy Agency. Activation Analysis of Hair as an Indicator of Contami- nation ofMan by Environmental Trace Element Pollutants. IAEA/RLU50, Vienna: 1978. 26. Olmez I. Instrumental neutron activation analy- sis of atmospheric particulate matter. In: Methods of Air Sampling and Analysis (Lodge JP Jr, ed). 3rd ed. Chelsea, MI:Lewis Publishers, 1989;143-150. 27. Schutz A, Skarping G, Skerfving S. Mercury. In: Techniques and Instrumentation in Analytical Chemistry: Trace Element Analysis in Biological Specimens, Vol 15 (Herber RFM, Stoeppler M, eds). Amsterdam, Elsevier, 1994;403-476. 28. Massachusetts Department of Public Health. Woburn childhood leukemia follow-up study. Boston, MA:Bureau of Environmental Health Assessment, Massachusetts Department of Public Health, 1996. 29. Iyengar GV, Kollmer WE, Bowen HJM. The Elemental Composition of Human Tissues and Body Fluids. New York:Verlag Chemie, 1978. 30. Takagi Y, Matsuda S, Imai S, Ohmori Y, Masuda T, Vinson JA, Mehra MC, PuTN BK, Kaniewski A. Trace elements in human hair: an

Volume 105, Number 10, October 1997 * Environmental Health Perspectives

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