The Forest Products Research Laboratory had requested that EPA approve the residential use of the preservative acid copper chromate, or ACC, on pressure-treated lumber.

Jim Jones, head of EPA’s pesticide office, said the preservative poses a cancer risk to workers who apply the material and those who process the lumber because of its high concentration of a particularly toxic form of chromate. The preservative also would pose other health risks, including severe skin irritation, to homeowners, children and contractors who come in contact with the lumber, he said.

Another preservative, chromate copper arsenate, or CCA, has been phased out for use in pressure-treated wood since 2004 because it contained arsenic.

The industry had viewed ACC as a cheaper substitute than what is currently being used. The preservatives, which are applied by pressure, protect wood against fungi and insects. Because ACC contains high concentrations of hexavalent chromium, it is considered a health risk, the EPA concluded.

Hexavalent chromium, also known as chromium 6, is a known human carcinogen.