The Environmental Appeals Board is giving DuPont three more years to finish testing products that may be a source of the chemical PFOA.
The testing was mandated by the Environmental Protection Agency and is designed to determine the potential of chemicals used at DuPont's Chambers Works plant in New Jersey to break down into PFOA and similar chemicals.
The tests were to be concluded in December, but DuPont said it needed the extension to purify the products under study.
DuPont and other companies have already announced plans to phase out the use of PFOA in the manufacturing process by 2015. DuPont says the evidence indicates PFOA exposure does not pose a health risk.
DuPont uses PFOA at its Washington Works plant outside Parkersburg, West Virginia.