Skin proves poor portal for arsenic in treated wood

Earlier this year, under federal orders, U.S. lumber suppliers phased out production of most old-style pressure-treated wood—the greenish type that had been a mainstay of outdoor decks, play sets, and other unpainted structures (SN: 1/31/04, p. 74: Danger on Deck?). The Environmental Protection Agency had decided that the pesticides pumped into these boards—especially arsenic—pose a cancer risk to children who contact the wood.

A new study offers some assurance to owners of structures treated the old way, with chromated-copper arsenate, or CCA. The research finds that CCA residues aren’t easily absorbed through the skin, suggesting that having bare skin in contact with treated structures should pose little hazard, according to study-leader Ronald C. Wester of the University of California, San Francisco.

He and other toxicologists worked with rhesus monkeys, whose skin resembles people’s in its permeability to chemicals. For 8 hours, the researchers exposed small portions of the animals’ belly skin to water tainted with dissolved arsenic. Two weeks later, the scientists applied CCA-tainted residues scraped from treated wood to the same areas.

Skin exposed to arsenic-laced water absorbed some of the poison, as evidenced by its appearance in the animals’ urine over the 24 hours following exposure. However, Wester’s group reports in the June Toxicological Sciences that it found no arsenic excretion after CCA exposure, an indication that the animals hadn’t taken up detectable amounts of this poison in the tests.

Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.

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