Science News - June 23, 2004

DuPont disputes PFOA cancer claim

Rachel Petkewich People working in and living around a DuPont plant where PFOA, which is also known as C8, is used to create Teflon pans have elevated cancer rates.

Chemical giant DuPont is disputing a recent study that claims exposure to the perfluorooctanoic acid (PFOA) used to manufacture Teflon and other fluoropolymers at one of its chemical plants in West Virginia causes an increased risk of cancer. The company was reacting to a study that found plant workers and neighbors whose drinking water contains the perfluorinated compound have cancer rates several times higher than those of the general population.

Like perfluorooctane sulfonate (PFOS), which was once used to make the popular Scotchguard fabric protector, PFOA appears to be ubiquitous at low levels in humans living far from any obvious sources. The mystery of how these perfluoroalkyl acids get into people has prompted investigations by academic scientists, industry, and the U.S. EPA. PFOA is acknowledged to cause cancer in animals, but studies of industrially exposed workers have not shown a conclusive cancer link. A preliminary EPA risk assessment released last year raised the possibility that PFOA at levels close to those currently found in women’s blood might pose a developmental risk to children (Environ. Sci. Technol. 2003, 37, 201A–202A). EPA is due to release a more complete risk assessment this summer (www.epa.gov/opptintr/pfoa/).

However, in this case, the cancer concerns stem not from PFOA’s global distribution, but instead from local releases. DuPont’s Washington Works plant, located on the Ohio River, has used PFOA—also called C8—for more than 50 years. For most of that time, DuPont released PFOA into the air, local landfills, and the adjacent Ohio River. Groundwater around the plant also contains the perfluoroacid. PFOA water concentrations near the Washington Works plant range from about 1 part per billion (ppb) to 8 ppb. This concentration is substantially less than the 150 ppb level of concern established by West Virginia in 2002.

The West Virginia study was conducted by James Dahlgren, a toxicologist at the University of California, Los Angeles, on behalf of plaintiffs in a class action lawsuit filed against DuPont. The 2001 suit alleges that DuPont knowingly contaminated local water systems with PFOA and that the chemical causes adverse health effects. Dahlgren presented the data at the Society of Environmental Toxicology and Chemistry meeting in Prague, Czech Republic, in April this year.

Dahlgren and colleagues compared cancer incidence from three different sources for three different groups: a survey of 599 residents living near DuPont’s Washington Works plant in West Virginia, unpublished health records of more than 5000 DuPont employees that were obtained as part of the lawsuit, and data for cancer prevalence in the United States as a whole. The class action lawsuit includes all nearby residents who have PFOA levels of at least 0.5 micrograms per liter in their drinking water and have lived in the area for at least a year.

Dalgren and his colleagues found that plant neighbors and DuPont workers have similar kinds of cancer, with elevated rates for prostate cancer in young men and cervical and uterine cancer in women. They also found higher rates of uncommon cancers, such as non-Hodgkin's lymphoma, leukemia, and multiple myeloma.

The kinds of cancers and their presence in young people point to PFOA exposure, Dahlgren says. “These are unusual cancers in young people, people between 40 and 50 years old. They are endocrine-disruptor-type cancers—prostate, breast, cervical—and this pattern has been seen in prior studies of workers involved with perfluorinated chemicals,” he adds. “It’s possible that the explanation is some factor other than PFOA exposure, but the most likely explanation is exposure to PFOA and other perfluorinated compounds.”

“Based on what we have seen, we question the scientific validity of the conclusion in the report,” counters Robin Leonard, principal epidemiologist for DuPont. For example, he says, the study did not control for other factors that might affect cancer rates. “There is no indication that other factors impacting the health of populations were considered or analyzed,” Leonard charges.

Meanwhile, DuPont is conducting its own $1 million survey of possible PFOA effects on 750 volunteer employees at the Washington Works plant. The goal is to compare the results of employees who work in the company's Teflon unit, the area where PFOA is primarily used, and those who work elsewhere in the plant. —REBECCA RENNER

Related Web links

• DuPont C8 website; www.c8inform.com
• Environmental Group, Ohio Citizen Action Washington Works site; www.ohiocitizen.org/campaigns/dupont_c8/dupont_c8.html
• Environmental Working Group’s report on perfluorinated compounds; www.ewg.org/reports/pfcworld