Effects of Cca Wood on Non-target Aquatic Biota

Studies are reviewed that demonstrate the leaching of Cu, Cr, and As from pressure-treated wood in aquatic environments. The metals leached out accumulate in sediments near the wood (particularly bulkheads, which have more surface area for leaching than dock pilings). The metals also accumulate in organisms, including epibiota that live directly on the wood and benthic organisms, which live in sediments near the wood. Those inhabiting sediments closer to the wood accumulate higher levels of the contaminants. Other animals can acquire elevated levels of these metals indirectly as a result of consuming contaminated prey (trophic transfer). Once organisms have accumulated metals, they may exhibit toxic effects. Effects of CCA leachates in aquatic biota have been noted at the cellular level (e.g. micronuclei, indicating DNA damage), tissue level (e.g. pathology), individual organism level (e.g. reduced growth, altered behavior, and mortality), and community level (reduced number of individuals, reduced species richness, and reduced diversity). Effects are more severe in poorly flushed areas and in areas where the wood is relatively new. Residential canals lined with CCA wood are particularly toxic. The severity of effects is reduced after the wood has leached for a few months. Deleterious effects in the aquatic environment appear to be due largely to copper. Thus, alternative formulations that lack Cr and As due to concerns about their toxicity to humans, but contain greater amounts of Cu and leach more Cu will be more deleterious than CCA to the aquatic environment.