Concerns over common perfluorinated surfactant

Perfluorooctanoic acid (PFOA), a perfluorinated surfactant produced in the United States by DuPont and used in the manufacture of Teflon, Goretex, and stain-resistant carpets, may pose a developmental risk to children at concentrations already found in the blood of women and children, according to a U.S. EPA preliminary risk assessment released on April 14.

“The data before us raise concerns,” according to Steve Johnson, Office of Pollution Prevention and Toxics assistant administrator who announced that the agency is accelerating its investigation of PFOA because of the analysis. The agency is also taking the unusual step of publicly negotiating enforceble consent agreements with the manufacturers and users to require research and reduce PFOA emissions. But the agency is not considering emergency action at this time because there is too much “scientific uncertainty” about the sources and pathways of PFOA exposure in the general population and too much uncertainty about the animal testing data, he said.

PFOA, sometimes referred to as C-8, has widespread applications in chemical manufacturing, aircraft production processes, and some electronic products. Following the unexpected discoveries concerning the environmental fate and toxicity of perfluorooctane sulfonates (PFOS) (Environ. Sci. Technol. 2001, 35, 154A–160A), EPA began investigating PFOA.

PFOA is a persistent pollutant and small concentrations are found in human blood, according to the risk assessment. Unlike PFOS, PFOA does not appear to biomagnify in animals. However, an ongoing, five-year study of nine retired 3M workers suggests a mean serum PFOA half-life of 4.37 years, indicating the potential for bioaccumulation in humans, according to the preliminary risk assessment.

EPA doesn’t know how people are being exposed to PFOA, according to Johnson. It may be released during manufacturing or processing, and it may also be formed due to the breakdown of other fluorinated compounds made by the telomerization process. Scientists who are studying the problem hypothesize that PFOA, which is nonvolatile, is a breakdown product of more volatile precursors, including telomers, according to environmental chemist Scott Mabury of the University of Toronto (ES&T on-line news, December 12, 2001).

EPA’s draft report assesses current scientific work, including studies by various perfluorinated chemical manufacturers. The document reviews human occupational studies and animal toxicological studies, focusing on adverse developmental effects observed in a two-generation rat study completed in March 2002 by contract lab Argus Research in Horsham, Pa.

In that study, rat pups whose dams received PFOA experienced delays in maturation and increased mortality. At the lowest dose with observed effects, the male pups lost weight, and this indicator was used for the risk assessment. Significantly, the difference between the PFOA rat dams’ blood concentrations and those measured in the blood from groups of children and women is less than 100-fold. This is a slim margin of safety that could be a cause for serious concern, say experts. However, using the concentration of PFOA in the male rats’ blood gives a difference of more than 9000, because female rats eliminate the perfluorinated compound much quicker than the males.

The EPA preliminary risk assessment is at odds with a risk assessment published in August 2002 by the West Virginia Department of Environmental Protection. The state’s assessment evaluated many of the same studies but decided that effects to the liver were of most concern and concluded that current environmental concentrations of PFOA pose no risk to human health. The West Virginia assessment stemmed from a consent order between the state and DuPont, following the discovery of PFOA from the company’s facility in public water supplies there, and in nearby Ohio. A panel of toxicologists, including several from EPA, proposed a reference dose of 0.004 milligrams per kilogram body weight per day. This converts to a drinking water concentration of 150 parts per billion—much higher than any currently known environmental concentration, assuming a 60 kilogram adult drinks 2 liters of water each day.

EPA’s effort to negotiate binding research agreements with companies that manufacture and use PFOA, as well as companies that manufacture telomers, began with letters of intent that were released on April 14. The members of the Fluoropolymer Manufacturers Group (Asahi Glass Fluoropolymers, USA; Daikin America; DuPont; and Dyneon) who together represent most of the known users and manufacturers of PFOA, outlined in these letters of intent to reduce emissions from their plants that use or manufacture PFOA by a minimum of 50% by 2006 as compared to a baseline determined in 2002.

Another group of companies has formed the Telomer Research Program (TRP—Asahi Glass, Clariant, Daikin, and DuPont). These companies are involved because there is some evidence that telomers can degrade to PFOA. TRP has hired a research lab to analyze for PFOA in finished carpets, textiles, and paper products that use telomer compounds. A report of the findings is expected this summer. Analysis of used products is expected before the end of the year.

Although DuPont maintains that existing data do not show an association between PFOA exposure and adverse human health effects, the company is continuing its study of the compound and has been working with federal and state agencies to determine human health-based screening levels for PFOA, according to a company spokesperson. —REBECCA RENNER