An Investigation of Homes with High Concentrations of PCDDs, PCDFs, and/or Dioxin-Like PCBs in House Dust

Abstract

As part of the University of Michigan Dioxin Exposure Study, the 29 congeners of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and dioxin-like polychlorinated biphenyls that have World Health Organization consensus toxic equivalency factors were measured in house dust from 764 homes using a population-based sampling design over selected regions in five Michigan counties. Twenty homes had a total toxic equivalency in house dust that was more than 2.5 standard deviations above the mean (i.e., defined to be outliers). This follow-up investigation describes the outlier house dust measurements and corresponding soil measurements and explores possible sources of these toxins in house dust. The congener distributions in the house dust outliers varied and were dominated (i.e., >50% of the total toxic equivalency) by either polychlorinated dibenzo-p-dioxins (n = 9), polychlorinated dibenzofurans (n = 1), or dioxin-like polychlorinated biphenyls (n = 9). Likely sources of contamination of house dust were identified in only three cases. In two cases, dust contamination appeared to be related to contaminated soil adjacent to the home; in one case, contamination was related to a source within the home (a carpet pad). In most cases, the source(s) of contamination of house dust could not be identified but appeared likely to be related to uncharacterized sources within the homes.

[Supplementary materials are available for this article. Go to the publisher's online edition of the Journal of Occupational and Environmental Hygiene for the following free supplemental resource: a PDF file containing a summary of baseline and dust outlier interview questions and tables containing PCB, PCDD, and PCDF concentrations in various samples of house dust and soil.]

Keywords:

• dioxins
• furans
• house dust
• polychlorinated biphenyls

ACKNOWLEDGMENTS

Financial support for this study comes from the Dow Chemical Company through an unrestricted grant to the University of Michigan. The authors acknowledge Sharyn Vantine for her continued assistance and Linda Birnbaum, Ronald A. Hites, Paolo Boffetta, and Marie Haring Sweeney for their guidance as members of our Scientific Advisory Board.

Notes

^A The floodplain of the Tittabawassee River (FP), the near-floodplain of the Tittabawassee River (NFP), the Midland plume area downwind from the historic incineration activities of the Dow plant (PL), elsewhere in Midland and Saginaw counties (MS), and Jackson and Calhoun counties that served as a control area (JC).

^B See supplemental Table I for details of interview questions.

^C TEQ calculated based on WHO 2005 TEFs. All TEQ results are reported as parts per trillion (ppt) on a dry weight basis.

^A The floodplain of the Tittabawassee River (FP), the near-floodplain of the Tittabawassee River (NFP), the Midland plume area downwind from the historic incineration activities of the Dow plant (PL), elsewhere in Midland and Saginaw counties (MS), and Jackson and Calhoun counties that served as a control area (JC).

^B See supplemental Table I for details of interview questions.

^C Some answers are approximate to protect the confidentiality of respondents.

^D Two woodburning fireplaces in the building, but not used since 1965.

^G Pipe only; no cigarettes.

^F Respondent only; no information on other members of household.

^E None since 1985.

^A The floodplain of the Tittabawassee River (FP), elsewhere in Midland and Saginaw counties (MS), and Jackson and Calhoun counties that served as a control area (JC).

^B All concentrations below the LOD were substituted with LOD/√2.

^C TEQ calculated based on WHO 2005 TEFs. All results are reported as parts per trillion (ppt) on a dry weight basis.

^A TEQ calculated based on WHO 2005 TEFs.