In vitro bioaccessibility of copper azole following simulated dermal transfer from pressure-treated wood

Micronized copper azole (MCA) and micronized copper quaternary (MCQ) are the latest wood preservatives to replace the liquid alkaline copper and chromated copper arsenate preservatives due to concerns over the toxicity or lack of effectiveness of the earlier formulations. Today, the use of MCA has become abundant in the wood preservative industry with approximately 38millionlbs of copper carbonate being used to treat lumber each year. Despite this widespread usage, little information is available on the bioaccessibility of this preservative upon gastrointestinal exposure. Using a simulated hand-to-mouth/gastric system exposure study we investigated several types of commercially available copper-treated lumber products as-purchased and after exposure to outdoor weathering conditions. Soluble and particulate fractions of copper were measured after transfer to and release from surface wipes passed along copper-treated lumber and exposed to synthetic stomach fluid (SSF, pH1.5) or deionized (DI) water. Wipes passed along new boards contained greater amounts of copper than wipes from weathered boards. The total copper recovered from the wipes after microwave extraction varied among the different wood types. For all wood types the copper released into SSF was more soluble than what was soluble in DI water. The data suggest that copper from treated wood is highly bioaccessible in SSF regardless of wood type and weathering condition.