DuPont Co. has agreed to a tougher, temporary standard for a chemical used to make Teflon and says it will test more drinking-water supplies for contamination near its Washington Works plant along the Ohio River.

If levels for ammonium perfluorooctaonate, also known as C8 or PFOA, exceed the new threshold — now 300 times stricter — DuPont would be required to filter the water or provide residents with an alternative supply, according to a consent agreement between the company and the U.S. Environmental Protection Agency.