I rarely know enough about pond topics to contribute anything useful. So I read and learn. The accumulated knowledge available in this forum is most remarkable.
I spent a military career in public health and near the end had responsibility for the Army's food analysis and diagnostic laboratory. I would like to add something about the toxicity of pressure treated wood in building piers. I know we all have to die of something, but I don't want it to be cancer. Most of us are old enough to have seen someone we knew well auger in with cancer. It's almost always pretty savage near the end. I believe that much of that cancer is avoidable. And it is almost impossible to know the precise effects of various carcinogens on humans. Until they allow us to do toxicologic testing on convicts and Jihadists, human studies are retrospective or speculative based on work in other species. There can be huge differences between much more closely related species. For example, the lethal dose for a known carcinogen, aflatoxin, is more than 30 times higher for a mouse than it is for a rabbit. My point is that we should all avoid all known carcinogens, at least when it is not too hard to do so.
I found lots of peer-reviewed articles on the dangers of the leached components of pressure treated wood. Pretty bad stuff. Lots of known carcinogens and primary toxins. Here is a brief abstract:
The effects of using wood treated with chromated copper arsenate in shallow-water environments: A review
Weis, JS; Weis, P
Estuaries.
Studies published over the past several years have documented that copper, chromium, and arsenic leach from pressure-treated wood placed in estuaries, and that these toxic metals accumulate in nearby sediments and biota. We have found bioaccumulation and deleterious effects in the epibiotic ("fouling") community, particularly in poorly flushed areas and on new wood. The epibiota showed reduced species richness, diversity, and biomass. Barnacles and encrusting bryozoa that settled on new treated wood grew more slowly than those that settled on untreated wood or plastic substrate. In laboratory studies, trophic transfer of the contaminants from epibiota to their consumers has also been demonstrated. We have also found accumulation of the treatment metals in the fine-grained fraction of nearby sediments and in the benthic infauna. Infauna also had reduced species richness and diversity in sediments adjacent to treated-wood structures. While standard toxicity tests with amphipods did not demonstrate acute toxicity of these sandy sediments, sublethal effects on development were seen in juvenile mysids. Overall, the extent and severity of effects of pressure-treated wood in an estuary depends on the amount and age of the wood and the degree of dilution by water movements.
Anyway, that my two bits. Tom Pool
