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Exposure Investigation Report



  1. Blood dioxin levels were elevated in residents of Mossville who participated in the EI. The median and mean concentrations of dioxin TEQs in the EI participants were greater than the 95th percentile concentration of a comparison population.

  2. The blood levels of many, but not all, of the individual dioxin-like compounds were elevated in the EI participants. The levels of 1,2,3,7,8 pentachlorodibenzo-p-dioxin were particularly elevated and were the most significant contributor to the dioxin TEQ total.

  3. Blood dioxin levels were primarily elevated in older residents of Mossville (> 47 years old).

  4. The blood dioxin concentrations measured in the EI participants are unlikely to be associated with known clinical health effects such as chloracne or elevated liver enzyme levels.

  5. Dioxin TEQ concentrations in four surface soil samples and two chicken eggs were not at levels of health concern.

  6. The concentration of dioxin TEQs in a breast milk sample was not elevated.

  7. The source of the increased dioxin exposure in residents of Mossville is not known.


  1. Evaluate potential pathways for human exposure to dioxin from environmental and dietary sources.

  2. Reduce human exposures to dioxin from significant exposure pathways that are identified.

  3. Further characterize the extent of dioxin exposure in the community.

  4. Evaluate strategies to assess past exposures to dioxin.

  5. Examine health status indicators for the community including cancer incidence statistics.

David J. Hewitt, M.D.
Medical Officer
Kenneth G. Orloff, Ph.D.
Senior Toxicologist


ATSDR gave the participants their individual test results and provided an explanation of their significance. ATSDR also held a public availability session to allow the participants to discuss their test results with environmental and health officials.

ATSDR (Division of Health Education and Promotion) facilitated access to an Association of Occupational and Environmental Clinics (AOEC) environmental medical expert in dioxin to review medical information for the 28 EI participants and determine the next clinical steps for these individuals. The AOEC environmental physician provided the 28 individuals with education and information regarding their exposure status.


ATSDR will work with Federal and State agencies and the community to implement further investigations to identify possible sources of dioxin exposure in the Mossville community.

ATSDR (Division of Health Studies) will review both the dioxin data and further environmental characterization data to determine if a more extensive exposure investigation or a health study follow-up is appropriate.

The United States Environmental Protection Agency, Region VI, will develop activities to evaluate human exposure pathways to hazardous substances in the environment. These activities will include: (1) air toxics monitoring in the Mossville area (to be conducted in conjunction with the Louisiana Department of Environmental Quality) and (2) sediment and water sampling of estuaries. Groundwater monitoring of public and private drinking water wells has been completed. Clean-up of the Chicot Aquifer is in progress.

The Louisiana Department of Health and Hospitals/Office of Public Health will: (1) assist ATSDR with follow-up health studies, (2) prepare a health consultation, in cooperation with ATSDR, consisting of a health statistics review of appropriate health outcomes, (3) provide, in cooperation with ATSDR, health professional education in Calcasieu Parish in the form of mailouts and presentations at grand rounds and/or local hospitals to physicians and other health professionals, and (4) provide information to the public on the Louisiana Children's Health Insurance Program.


  1. Agency for Toxic Substances and Disease Registry; Health Consultation for Calcasieu Parish; October 16, 1998.
  2. U.S. Environmental Protection Agency; Estimating Exposure to Dioxin-Like Compounds Volume II: Properties, Sources, Occurrence and Background Exposures; June 1994; EPA/600/6-88/005Cb.
  3. D.G. Patterson, S.G. Isaacs, L.R. Alexander, et al.; Method 6: Determination of specific polychlorinated dibenzo-p-dioxins and dibenzofurans in blood and adipose tissue by isotope dilution-high-resolution mass spectroscopy; Environmental Carcinogen Method of Analysis and Exposure Measurement 299-342 (1991).
  4. U.S. Environmental Protection Agency; Estimating Exposure to Dioxin-Like Compounds - Volume III: Properties, Sources, Occurrence and Background Exposures; June 1994; EPA/600/6-88/005Cc.
  5. M. Van den Berg, L. Birnbaum, A. Bosveld, et al.; Toxic Equivalency Factors (TEFs) for PCBs, PCDDs, PCDFs for humans and wildlife; Environmental Health Perspectives 106 (12) 775-792 (1998).
  6. U.S. Environmental Protection Agency; cited in U.S. EPA; Estimating Exposure to Dioxin-Like Compounds Volume II: Properties, Sources, Occurrence and Background Exposures; page 5-19, June 1994; EPA/600/6-88/005Cb.
  7. O. Papke et al.; cited in International Agency for Research on Cancer; IARC Monographs on the Evaluation of Carcinogenic Risks to Humans: Polychlorinated Dibenzo-para-dioxins and Polychlorinated Dibenzofurans; Volume 69, pg 114, 1997.
  8. P. Furst, C. Furst, and K. Wilmers; Human milk as a bioindicator for body burden of PCDDs, PCDFs, organochlorine pesticides, and PCBs.; Environmental Health Perspectives Supplements 102 Suppl 1:187-193 (1994).
  9. L.L Needham, D.G. Patterson, V.W. Burse, et al.; Reference Range Data for Assessing Exposure to Selected Environmental Toxicants; Toxicol. Indus. Health; 12 507-513 (1996).

  10. R. E. Alcock and K.C. Jones; Dioxins in the environment: A review of trend data; Environmental Science and Technology 30 3133-3143 (1996).
  11. Micromedex, Inc.; TOMES CPS System; Hazardous Substances Data Bank; 1999.
  12. Jean Cruczwa and Ronald Hites; Airborne dioxins and dibenzofurans: Sources and fates; Environ. Sci. Technol 20(2) 195-200 (1986).
  13. J. Theisen, W. Funcke, E. Balfanz, and J. Konig; Determination of PCDFs and PCDDs in fire accidents and laboratory combustions tests involving PVC-containing materials; Chemosphere 19 423-428 (1989).
  14. D. Flesch-Janys et al; Elimination of polychlorinated dibenzo-p-dioxins and dibenzofurans in occupationally exposed persons; J Tox. Env. Health 47 363-378 (1996).
  15. Agency for Toxic Substances and Disease Registry; Case Studies in Environmental Medicine: Dioxin Toxicity; June 1990.
  16. L.C. Dickson et al.; Health Risks of "dioxins": a review of environmental and toxicological considerations; Vet Hum Toxicol 35 68-77 (1993).
  17. Agency for Toxic Substances and Disease Registry; Toxicological Profile for Chlorinated Dibenzo-p-Dioxins (Update); December 1998.
  18. K. Steenland, L. Piacitelli, J. Deddens, M. Fingerhut, and L.I. Chang; Cancer, heart disease, and diabetes in workers exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin. JNCI 91 779-786 (1999).

  19. M.J DeVito, L.S. Birnbaum, W.H Farland, and T.A. Gasiewicz; Comparisons of estimated human body burdens of dioxin-like chemicals and TCDD body burdens in experimentally exposed animals; Environmental Health Perspectives 103(9) 822-831 (1995).
  20. A. Schecter et al.; cited in U.S. Environmental Protection Agency; Estimating Exposure to Dioxin-Like Compounds Volume II: Properties, Sources, Occurrence and Background Exposures; page 5-29; June 1994; EPA/600/6-88/005Cb.
  21. C.T. De Rosa, D. Brown, R. Dhara, et al.; Dioxin and Dioxin-Like Compounds in Soil, Part 1: ATSDR Interim Policy Guidance; Toxicology and Industrial Health 13 759-768 (1997).
  22. F. Schuler, P. Schmid, and C. Schlatter; The transfer of polychlorinated dibenzo-p-dioxins and dibenzofurans from soil into eggs of foraging chicken; Chemosphere 34 711-718 (1997).

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