Researchers want to know how long a chemical used to produce Teflon (C8) remains in the body.

The review will expand an ongoing study of mid-Ohio Valley residents on whether the chemical, referred to as C8, is harmful to human health.

The chemical has been at the center of a storm between DuPont Corporation and citizens of the Ohio valley.

Residents in West Virginia and Ohio sued DuPont Company in 2001 charging that the company's Washington Works plant near Parkersburg had contaminated their water supplies.

To settle the class-action lawsuit, the company agreed to fund a health screening for up to 70,000 residents.

The latest turn, a science panel charged with looking at health histories and blood samples from residents wants to expand the study to determine how long C8 stays in the body.

Over the next four years about 200 residents who receive their water from Little Hocking, Ohio, and Lubeck water systems will be paid to provide blood samples.

The two water systems were selected because both are expected to begin using carbon filters that are designed to remove C8 from the water.