Aquatic ecological risks posed by tributyltin in United States surface waters: Pre-1989 to 1996 data

Acute and chronic risks to aquatic life from exposure to tributyltin (TBT) in surface waters were assessed probabilistically using more than 9 years of monitoring data. More than 50 sites around the United States were sampled, representing six saltwater regions and one freshwater (Lake Erie). Ambient TBT concentrations were compared to acute and chronic effect thresholds to estimate risks for each year (1986-1988 and 1992-1996), site type, and region. Site types comprised commercial harbors, shipyards, marinas, and fish/shellfish habitats proximate to these commercial areas. Tributyltin concentrations in surface waters have declined in all regions and site types since passage of the Organotin Antifouling Paint Control Act in 1988. No risks of acute toxicity have been suggested since 1994. Chronic risks have remained highest in marinas compared to other site types but have declined from a risk involving 25% of the species prior to 1989 to one involving 6% of the species in 1996. Risks associated with commercial harbors and shipyards have been similar (4-6%) since 1994. Chronic risks have been less than or equal to 1% in fish and shellfish habitats sampled <1 to 2 km from TBT sources. Risks in Galveston Bay, over all years (1-19%), have been greater than in the other regions (less than or equal to 9%).