C8 panel moving closer to key decisions
CHARLESTON, W.Va. -- More than six years after a landmark legal settlement, a panel of scientists is still another year away from determining if the DuPont chemical C8 makes people sick. But with three new reports issued last month, members of the three-person C8 Science Panel say they are getting closer to a conclusion.
The latest "status reports" on the panel's work contain the same cautionary points the group has emphasized since issuing its first results in October 2008: Data is missing on whether health impacts or chemical exposure came first. Cause-and-effect in such situations is hard to prove. More research is needed.
Still, in its most recent reports, the Science Panel used much stronger language than it ever has before.
• One status report said an association between C8 exposure and increased markers of potential liver disease was "highly statistically significant" and "unlikely to be due to chance."
• Another study reported "no association" between C8 and preterm births, low birth weight or birth defects.
• The third report concluded that increased risk of kidney cancer death "could possibly be due to" C8 exposure.
Science panel members, in interviews last week, said such language shouldn't be taken as a sign they've made up their minds, but does indicate they are moving closer to a final answer.
"We're not there yet, but these are very important building blocks -- more important than a lot of what came before," said panel member David Savitz, a professor of community health at Brown University.
Savitz and the rest of the Science Panel are working to implement a key provision of a $107.6 million class-action settlement between DuPont and about 70,000 residents whose drinking water was polluted by C8 from the company's Washington Works plant south of Parkersburg.
C8 is another name for perfluorooctanoate acid, or PFOA. In West Virginia, DuPont has used C8 since the 1950s as a processing agent to make Teflon and other nonstick products, oil-resistant paper packaging and stain-resistant textiles.
DuPont and other companies have reduced their emissions and agreed on a voluntary phase-out of the chemical, but researchers are still concerned about a growing list of possible health effects and about the chemical's presence in consumer products, as well as continued pollution from waste disposal practices.
Savitz and panel members Kyle Steenland and Tony Fletcher were appointed to study C8 and determine if there is a "probable link" between exposure and illness. If they conclude there is, DuPont could be on the hook for up to $235 million for future medical monitoring for area residents.
The term "probable link" isn't a standard one for scientists who study toxic chemical exposure. It's defined in the DuPont legal settlement as whether, "based upon the weight of the available scientific evidence, it is more likely than not that there is a link between exposure to C8 and a particular human disease" among Mid-Ohio Valley residents taking part in the suit.
Currently, the Science Panel's schedule calls for a probable link determination by July 2012. In May, Wood Circuit Judge J.D. Beane blasted the scientists for taking so long, and some residents in the Parkersburg area are also becoming impatient with the panel's timetable.
"I'm seeing a lot of sashaying around the block," said Joe Kiger, one of the lead plaintiffs in the suit against DuPont. "They keep coming up with association after association, but they haven't said 'probable link' yet."
The Science Panel has previously published peer-reviewed papers and separate reports to the court that found C8 exposure associated with a variety of adverse health effects, ranging from high cholesterol and hypertension to birth defects and learning disorders in children. So far, though, the panelists have not filed a report in which they actually either find or rule out a "probable link" between such problems and C8 exposure.
In its three most recent status reports, the Science Panel focused on its study of DuPont plant worker mortality, potential impacts on liver function tests, and birth outcomes among mothers exposed to C8. Complete data from those studies has not yet been made public, and the results have not gone through peer review or been published in scientific journals.
The worker mortality results are in some ways the most significant, because DuPont has been criticized before by its own panel of corporate science advisers for downplaying a potential link between C8 and higher risk of kidney cancer death among workers.
In its status report, the Science Panel said it found no increase in kidney cancer deaths or deaths from non-cancer kidney disease when it compared DuPont workers to the general U.S. population. Overall mortality rates among DuPont workers were also low, when compared to the general population.
Science Panel members explained that is to be expected, because of something scientists call "the healthy worker effect."
"Almost all worker populations, when compared to the general population, have a lower mortality rate for all causes," said panel member Kyle Steenland of Emory University, the lead researcher on the study. "Working populations don't tend to have sick people.
"If you just compare the workers to the general population, you often see depressed or lower rates of mortality among the workers," Steenland said. "If you want to pinpoint the effects on the mortality in the workforce, it often helps to compare workers with different exposures."
That's just what the Science Panel did, and the results "significantly increased rates of death among the more highly exposed workers compared to the low-exposed workers" for kidney cancer and non-cancer kidney disease.
The Science Panel cautioned that these results, while "statistically significant," were also based on small numbers -- 12 kidney cancers and 13 chronic kidney disease cases.
But the panel also said, "the increased risk for the more highly exposed in relation to malignant kidney and non-malignant kidney diseases could possibly be due to PFOA; the kidney is a site in the body where PFOA is found."
In its study of C8 and markers of potential liver disease, the Science Panel found an association between exposure and one of three liver enzymes that it examined. It said that association -- between C8 exposure and the liver enzyme ALT -- "is unlikely to be due to chance, as it is highly statistically significant."
The results concerning C8 exposure and the other two liver enzymes, GGT and bilirubin, were not as definitive.
The Science Panel status report said neither of those two enzymes "showed a clear relationship with PFOA."
In an email interview, panel member Tony Fletcher of the London School of Hygiene and Tropical Medicine said the detailed data about the other enzymes and C8 would be released once a formal scientific paper is published.
But, Fletcher said, the pattern of comparisons between C8 exposures and the other enzymes was "not completely flat," but that the "pattern is less convincing" than with ALT.
While Fletcher said his personal conclusion is there is "little or no evidence of an association, he also said the results "are insufficient to prove an association, but also insufficient to conclude there is no association," Fletcher said.
The Science Panel's report on pregnancy and birth outcomes found a "small but clearly present" association between C8 exposure and pre-eclampsia, a condition involving high blood pressure in pregnant women.
The panel's status report indicated this was the first and only study addressing that issue. But actually, the Science Panel itself previously published a status report and a peer-reviewed paper that found a similar association between C8 and pre-eclampsia.
That earlier study, first made public in March 2009, also found what was characterized as a "weak" association between C8 exposure and birth defects.
Initially, the Science Panel had examined pregnancy and birth outcomes for 1,845 pregnancies between 2000 and 2006. The more recent report, which found no association between C8 and birth defects, miscarriages or stillborn births, examined a much larger number, nearly 12,000 pregnancies between 1990 and 2005.
Science Panel member David Savitz, the leader researcher on the issue, said the much larger number of pregnancies studied makes the more recent results far more likely to be accurate.
"We believe the newer information is more solid and more informative than the old one," Savitz said. "I'm more comfortable than I was before about these results."
Savitz cautioned that the new Science Panel report does not contradict the findings of a 2007 Johns Hopkins study that linked C8 exposure to low birth weights. The Science Panel only examined whether babies were above or below a certain weight of concern -- 5.5 pounds -- while Johns Hopkins researchers looked much more precisely at small changes in actual weight of babies compared to C8 levels in umbilical cord blood.
Savitz also noted that there haven't been many previous studies about C8's impact on pregnancies.
"This is very strong evidence," Savitz said. "But one study is one study. To be absolutely certain requires replication. I don't want to say the case is closed. It's not."
DuPont emphasizes that the Science Panel has more studies scheduled and that those need to be "completed before any conclusions could be drawn regarding cause and effect."
But at least one other scientist who is studying the Mid-Ohio Valley C8 data believes the Science Panel is being too cautious. Dr. Alan Ducatman is leading a West Virginia University team that is examining the C8 data and publishing papers about the results.
During a May hearing, Ducatman told Beane that there is no doubt that C8 exposure is linked to at least one adverse health effect -- high cholesterol levels.
"There is zero doubt of that," Ducatman testified. "I think assuming we accept high cholesterol as a disease that we treat with real medications with real side effects and real consequences for patients, there is ... a probable link."
Reach Ken Ward Jr. at firstname.lastname@example.org or 304-348-1702.