Effectiveness of CCA fixation to avoid hexavalent chromium leaching

It is generally assumed that hexavalent chromium in wood treated with chromated copper arsenate (CCA) preservative is substantially reduced to trivalent chromium during fixation and that the potential to leach the more toxic CrVI is minimal. However, there are occasional claims that some hexavalent chromium remains in wood after fixation and that small amounts of CrVI are available for leaching. A number of CCA-treated wood samples of different wood species and ages, as well as wood-cement and wood-plastic composites containing CCA-treated wood were collected and exposed to laboratory leaching. The leach water and expressate from water-saturated wood samples were analyzed for CrVI, total Cr, Cu, and As. For CCA-treated wood and wood-plastic composites, CrVI in the leachate was near or below the detection limit for analysis by ion chromatograph (less than 1 ppb) compared to total chromium levels of 200 to 2,700 ppb.The amount of hexavalent chromium relative to total chromium leached was generally less than 0.1 percent. Leachate from wood-cement composites showed significant levels of CrVI (up to 50% of the total chromium leached). However, both hexavalent and total chromium levels in the leachate were low (200 to 400 ppb). These results show that once the CCA is properly fixed in wood, there is little health or environmental risk associated with toxic hexavalent chromium being released from treated wood by water leaching.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member