Internal Warnings
Signs of potential risks go back 50 years

* 1951 -- DuPont begins using ammonium perfluorooctanoate, also called C8, to make Teflon and related polymers at its Washington Works plant near Parkersburg, W.Va. The chemical is produced by Minnesota Mining and Manufacturing, or 3M.

* 1954 -- DuPont employees express concerns about the toxicity of C8.

* 1961 -- DuPont confirms that C8 is toxic in animals and causes observable changes in organ functions.

* 1978 -- 3M reports that C8 is detected in the blood of its workers. DuPont is ''disturbed'' that C8 might be causing ''toxic effects'' among employees at the Washington Works plant. The information is not shared outside the company.

* 1980 -- Additional study by 3M confirms that C8 is toxic to rats and monkeys. DuPont determines that ''people accumulate C8'' and ''continued exposure is not tolerable.'' The company begins sampling workers' blood for C8.

* 1982 -- DuPont's director of employee relations recommends that all ''available practical steps be taken to reduce this (C8) exposure because,'' among other things, ''all employees, not just Teflon area workers are exposed'' and ''there is obviously great potential for the current or future exposure of members of the local community from emissions leaving the plant perimeter.''

* 1984 -- DuPont sends employees to obtain drinking water samples from taps near Washington Works. C8 levels in the water are as high as 1.5 parts per billion in Lubeck, W.Va., and 0.8 parts per billion in Little Hocking, Ohio, where drinking water is drawn from wells across the Ohio River from the plant.

* 1988 -- DuPont buys the Lubeck well field next to Washington Works for $2 million and helps drill new wells 2 miles downriver.

* 1991 -- DuPont establishes a ''community exposure guideline'' of 1 part per billion for C8 in drinking water. The company continued to cite the guideline in internal documents as recently as November 2001.

* May 2000 -- Pressed by the U.S. Environmental Protection Agency, 3M announces it is ''voluntarily'' phasing out production of perfluorooctanyl sulfonate (the active ingredient in Scotchgard) and related chemicals, including C8.

* October 2000 -- DuPont reaches an out-of-court settlement with a West Virginia farmer who filed a lawsuit claiming that C8 killed his cattle and sickened his family.

* August 2001 -- Attorneys file a class-action lawsuit on behalf of West Virginia residents exposed to C8.

* November 2001 -- West Virginia and DuPont sign a consent order requiring another study of the potential health hazards posed by C8.

* January 2002 -- Officials from the Little Hocking Water Association find out for the first time that their water supply is contaminated with C8.

The West Virginia Department of Environmental Protection concludes that C8 in drinking water presents ''possible health risks to the public'' and that C8 ''has been linked to possible health problems related to long-term exposure.''

* February 2002 -- Tests of Little Hocking's wells detect levels of C8 that are nearly eight times higher than DuPont's community standard.

In a draft hazard assessment, the U.S. EPA concludes that cancerous tumors induced in rats exposed to C8 ''are relevant to humans.''

* March 2002 -- C8 is detected in the Tuppers Plains, Ohio, water system -- 15 miles downriver from Washington Works. Low levels of the chemical also are found in Pomeroy, Ohio, 70 miles downriver, and in the Belpre, Ohio, water system, 4 miles upriver from the plant. Experts conclude that smokestack emissions from Washington Works are causing some of the contamination.

Under an agreement with the U.S. EPA, DuPont promises to reduce air and water emissions of C8 by at least 50 percent of 1999 levels by the end of 2003. The company also plans to install a system to remove up to 95 percent of the C8 in the plant's wastewater.

* May 2002 -- A team of West Virginia, federal and private scientists convened by the state of West Virginia declares that water containing up to 150 parts per billion of C8 isn't harmful to humans.

* September 2002 -- The U.S. EPA begins a rare ''priority review'' of data that links C8 to health problems, the first step in a potential effort to regulate the chemical. The agency cites studies showing that ''exposure to (C8) can result in a variety of effects including developmental/reproductive toxicity, liver toxicity and cancer.''

West Virginia regulators approve an air-exposure level for C8 that is three times weaker than the limit proposed by an agency consultant, who says the lower level ''is more protective of public health.''

* December 2002 -- In an internal memo, a top official at the Ohio Environmental Protection Agency endorses West Virginia's C8 ''screening level'' of 150 ppb in drinking water. ''As a result, no adverse health effects would be expected to occur in populations using the contaminated water as a source of drinking water,'' the Ohio EPA memo concludes.

Sources: U.S. Environmental Protection Agency, Ohio Environmental Protection Agency, West Virginia Department of Environmental Quality, court documents