A Methodology for Estimating Human Exposure to Perfluorooctanoic Acid (PFOA): A Retrospective Exposure Assessment of a Community (1951–2003)

Abstract

Perfluorooctanoic acid (PFOA) is a persistent chemical that was recently shown to be widely distributed in the ambient environment. Because of concerns about the possible adverse health effects on persons exposed to PFOA, a retrospective exposure assessment was conducted for a population of about 50,000 persons who reside near one of the facilities where this chemical was used. No similar study of any chemical with the properties of PFOA had ever been performed; thus, several novel methods were developed and applied in this analysis. Historical records of the emissions from the facility were the basis for the estimates of the potential intake of (PFOA) by residents over the past 53 yr. Various well-accepted environmental models were dynamically combined in order to estimate the concentrations in all relevant environmental media including ambient air, surface soil, drinking water, and homegrown vegetables. Following considerable analyses, particulate deposition from facility air emissions to soil and the subsequent transfer of the chemical through the soil was determined to be the most likely source of PFOA that was detected in groundwater. The highest off-site environmental concentrations were predicted to occur about 1 mile away. For this approximately 1½ square mile area, during the time period 1951–2003, the model-estimated average air concentration was 0.2 μg/m³, the estimated surface soil concentration was 11 μg/kg, and the estimated drinking water concentration was 4 μg/L. Similar data were generated for 20 additional geographical areas around the facility. Comparison of measured PFOA concentrations in groundwater in the various water districts indicated that the models appeared to overpredict recent groundwater concentrations by a factor of 3 to 5. The predicted historical lifetime and average daily estimates of PFOA intake by persons who lived within 5 miles of the plant over the past 50 yr were about 10,000-fold less than the intake of the chemical not considered as a health risk by an independent panel of scientists who recently studied PFOA.

Acknowledgements

The research underlying this work and the preparation of this article were funded by DuPont. They have been involved in litigation regarding the presence of PFOA in groundwater at the facility described here. However, neither DuPont nor its legal counsel reviewed this article prior to publication.

Notes

^*Water samples were collected at Little Hocking Water Association, Lubeck Public Service District, City of Belpre, Parkersburg Water Department, Tuppers Plains/Chester Water District, Village of Pomeroy, Ravenswood Municipal, Mason County Public Service District, Village of Racine, New Haven Water Department, and Village of Syracuse.

^†Soil data available at http://www.epa.gov/waterscience/ftp/basins/gis_data/huc

3M Company. 2003. Final Report, Descriptive analyses of serum fluorochemical concentrations form Cottage Grove employee participants of the 2002 Medical Surveillance Program, 3M Medical Department, June 17, 2003. U.S. EPA Public Docket No. AR-226–1352, Washington, DC.

Alexander, B. H. 2001. Mortality Study of Workers Employed at the 3M Cottage Grove facility. St. Paul, MN: 3M Company. U.S.EPA Public Docket AR-226–1030a018, Washington, D.C.

Association of Plastics Manufacturers in Europe. 2003. Adsorption/desorption of ammonium perfluorooctanoate to soil (OECD 106). EMSE Study/Project EMSER TO111/14107. Report EMSER 17–03.

DuPont, 2002. Memo from M. Ann Bradley to Armando Benincasa and Dr. Dee Ann Staats of the West Virginia Department of Environmental Protection. Air dispersion modeling for Year 2000. June 13, 2002.

DuPont, 2003a. Revised groundwater flow model, DuPont Washington Works, Washington, WV. January 2003. DuPont Corporate Remediation Group and URS Diamond. EPA Docket OPPT-2003–0012, Document ID 0868.

DuPont, 2003b. Follow-up to September 15, 2003 submission of DuPont progress report on environmental assessments pursuant to the APFO users LOI dated March 14, 2003: Air dispersion modeling results. Letter to the Office of Pollution Prevention and Toxics from David M. Rurak of DuPont, dated October, 20, 2003. Containing the following attachments authored by DuPont: (1) Year 2002 Air Dispersion Modeling Analysis of APFO Emissions (October 17, 2003). and (2) September 2002 through August 2003 air dispersion modeling analysis of APFO emissions (October 17, 2003). EPA Docket OPPT-2003–0012, Document ID 0206, 0224, 0225.

DuPont, 2003c. Adsorption/desorption of ammonium perfluorooctanoate to soil (OECD 106). April 2003. E. I. du Pont de Nemours and Company Central Research and Development sponsored by Association of Plastic Manufacturers in Europe. EPA Docket OPPT-2003–0012, Document ID 0401.

West Virginia Department of Environmental Protection. 2002. Ammonium Perfluorooctanoate (C8) Assessment of Toxicity Team (CATT) Report—Final. August. EPA Docket OPPT-2003–0012, Document ID 0015.

West Virginia Department of Environmental Protection. 2003. Ammonium Perfluorooctanoate (C-8) Groundwater Investigation Steering Team Report. Final C-8 GIST Report. Division of Water and Waste Management. Charleston WV. August. EPA Docket OPPT-2003-0012, Document ID number 0204