A federal judge on Wednesday quizzed a toxicologist who says DuPont Co. has poisoned Parkersburg's city water supply with dangerous levels of the toxic chemical C8.

U.S. District Judge Joseph R. Goodwin questioned toxicologist David Gray's conclusion that residents are at increased risk of illness and in need of preventive medical monitoring.

Gray, an expert witness for residents, testified for most of the day in a case that seeks to make DuPont pay for clean water and medical testing for thousands of residents who weren't part of an earlier legal settlement with DuPont.

In a report filed in court, Gray proposed a C8 water quality limit of 0.02 parts per billion was needed to protect the public from any "appreciable risk."

That level is stricter than those included in a federal deal with DuPont or state regulations in Minnesota, New Jersey and North Carolina. Those limits range from 0.04 parts per billion to 0.5 parts per billion, Gray testified.

Among other testimony, Gray cited a recent study that found neurological effects on rats at extremely low exposure levels.

"This is an endpoint that shows up at a very low dose," Gray told the judge.

Goodwin is weighing a crucial decision: Whether to allow the case to move forward as one class action, rather than thousands of individual suits.

The judge cautioned he was "not impressed" with Gray's testimony that a federal government science panel found C8 is likely to cause cancer in humans. And Goodwin expressed skepticism that increased liver enzymes linked to C8 mean the same thing legally as a heightened risk of disease.

A ruling that certifies the class action could put pressure on DuPont to settle, while a ruling the other way would make fighting the company much more expensive and time consuming for the residents.

DuPont lawyers argue there are too many differences among residents - amount of water consumed, levels of C8 in that water, and a variety of individual health factors - to allow the case as a class action. Lawyers for the residents say their clients all share a common increased risk of illness from drinking water contaminated with DuPont's C8.

A federal judge on Wednesday quizzed a toxicologist who says DuPont Co. has poisoned Parkersburg's city water supply with dangerous levels of the toxic chemical C8.

U.S. District Judge Joseph R. Goodwin questioned toxicologist David Gray's conclusion that residents are at increased risk of illness and in need of preventive medical monitoring.

Gray, an expert witness for residents, testified for most of the day in a case that seeks to make DuPont pay for clean water and medical testing for thousands of residents who weren't part of an earlier legal settlement with DuPont.

In a report filed in court, Gray proposed a C8 water quality limit of 0.02 parts per billion was needed to protect the public from any "appreciable risk."

That level is stricter than those included in a federal deal with DuPont or state regulations in Minnesota, New Jersey and North Carolina. Those limits range from 0.04 parts per billion to 0.5 parts per billion, Gray testified.

Among other testimony, Gray cited a recent study that found neurological effects on rats at extremely low exposure levels.

"This is an endpoint that shows up at a very low dose," Gray told the judge.

Goodwin is weighing a crucial decision: Whether to allow the case to move forward as one class action, rather than thousands of individual suits.

The judge cautioned he was "not impressed" with Gray's testimony that a federal government science panel found C8 is likely to cause cancer in humans. And Goodwin expressed skepticism that increased liver enzymes linked to C8 mean the same thing legally as a heightened risk of disease.

A ruling that certifies the class action could put pressure on DuPont to settle, while a ruling the other way would make fighting the company much more expensive and time consuming for the residents.

DuPont lawyers argue there are too many differences among residents - amount of water consumed, levels of C8 in that water, and a variety of individual health factors - to allow the case as a class action. Lawyers for the residents say their clients all share a common increased risk of illness from drinking water contaminated with DuPont's C8.

"We are not dealing with one person facing a threat. We are not dealing even with a few people," said Steven Justice, one of the residents' lawyers. "We are dealing with a situation where thousands of people in the Parkersburg community are facing the same threat."

The class certification issue is being closely watched. DuPont is facing a similar lawsuit related to water pollution from its Chambers Works plant in Deepwater, N.J, and two dozen state-level class action suits that allege C8 leached from Teflon-coated pans.

C8 is another name for ammonium perfluorooctanoate, or PFOA. DuPont has used the chemical since the 1950s at its Washington Works plant south of Parkersburg. C8 is a processing agent used to make Teflon and other nonstick products, oil-resistant paper packaging and stain-resistant textiles.

Around the world, researchers are finding that people have C8 and other perfluorochemicals, or PFCs, in their blood in low levels. Evidence is mounting about the chemical's dangerous effects, but regulators have not yet set a federal standard for emissions or human exposure.

In September 2004, DuPont agreed to a $107.6 million settlement with residents of communities around Parkersburg. The money is funding two major studies of C8's health impacts, and DuPont also installed treatment systems to get the chemical out of local water.

But at the time the deal was made, C8 had not been found in the Parkersburg city water supply. Later, C8 was detected there. A follow-up lawsuit was filed.

During Wednesday's hearing, lawyers for the residents piled study after study about C8 in front of Goodwin. Justice led Gray through a long and detailed explanation of a risk assessment that is the basis for the class certification argument.

Last month, Goodwin scheduled the hearing after concluding he did not have enough information to decide whether to certify the class. The judge said he wanted to hear testimony from the residents' experts and question them himself in open court.

Under U.S. Supreme Court rulings, district judges like Goodwin are supposed to scrutinize class-action motions closely before approving them. Goodwin said such an analysis "is especially necessary in this suit, where the plaintiffs assert a medical monitoring cause of action and rely on their experts' opinions to prove both the merits of their case as well as the appropriateness of class certification."

The hearing continues today.

Reach Ken Ward Jr. at kw...@wvgazette.com or 348-1702.