Jerry Spencer had docks on the brain. 

The Isle of Palms resident was watching his neighbor build a new one into the salt marsh behind their backyards a few weeks ago when he decided he wanted to replace the decking on his own older dock. So he walked next door and peeled a label off a piece of wood, curious to see what company produced it. 

What he found was a lengthy warning statement about arsenic, saying that the wood should never be handled without gloves and should never be burned.

Wood treated with chromated copper arsenate was a material of choice for builders around the United States for decades because of its ability to withstand the elements. Bryan Strickland, a manager at Mount Pleasant building supply store Guy C. Lee, said CCA-treated pilings last in a marine environment like a marsh for longer than 30 years. 

No other type of lumber comes close, he said. 

But in the late-1990s, a steady stream of scientific studies showed that arsenic can leak out of the materials, potentially coming in contact with people. 

Arsenic is a known carcinogen in small quantities and in larger quantities was a poison of choice centuries ago, said Vijay Vulava, who researches environmental chemistry and pollution at the College of Charleston. And chromate, another component of CCA, has also long been linked to cancer.

While CCA was never formally banned by the Environmental Protection Agency, it hasn't been used for homes, indoor building or outdoor decks in the United States since 2004. 

The main health concern stems from CCA-treated wood coming into contact with people directly, such as by touching bare hands or feet, Vulava said. While the chemicals may leak into the water, toxicity is dependent on how concentrated the chemical is, and the water movement in a tidal marsh would likely disperse the compound quickly. 

"There is just too much dilution that happens along the way that we would be exposed to it incidentally later on," Vulava said.

Matthew Flemming, the man who was having the dock built in Isle of Palms, said the CCA-treated wood isn't being used for the decking and rails along his dock, only for pilings and other structural support. Strickland confirmed that that's how manufacturers recommend using the wood — only for support structures that people won't typically touch. 

Flemming has children, and he said his priority for his family was building a dock that will last. 

"I think that's more of a safety concern for the kids (than CCA) — having a dock fall apart," he said. 

A representative of his contractor, Palmetto Dock and Salvage, declined to comment. 

What's still unclear, however, is whether the CCA that does leach into the water — and it inevitably will, Vulava said — would have a noticeable impact on the surrounding environment. 

Determining the environmental effects would require more study, Vulava said.

The S.C. Department of Health and Environmental Control doesn't regulate building materials in the coastal zone, spokesperson Cristi Moore wrote in an email. She wrote that the chemical is not part of the state agency's regulatory authority. 

But Spencer still worries about putting harsh chemicals in contact with a delicate coastal environment. 

"When it rains, it's got to run into the marsh," Spencer said. 

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IOP Dock

Isle of Palms resident Jerry Spencer explains his concerns Friday about the dock his neighbor is building. The dock is being built in part with chemical-treated lumber that contains arsenic. Brad Nettles/Staff

Reach Chloe Johnson at 843-735-9985. Follow her on Twitter @_ChloeAJ.