An ecological risk assessment for the use of Irgarol 1051 as an algaecide for antifoulant paints

Irgarol 1051 is an algaecide used in copper-based antifoulant paints for co ntrolling fouling organisms on the hulls of recreational and commercial wat ercraft. Paints containing this algaecide have been used in Europe since th e mid-1980s. In 1998, the first antifouling paints containing Irgarol 1051 were registered for use in the U. S. To examine the risk that Irgarol may p ose to aquatic ecosystems, a probabilistic ecological risk assessment was c onducted using distributions of exposure and toxicity data. Exposure data f or this assessment were derived from 11 monitoring studies (146 stations) c onducted in marinas, estuaries, and coastal waters from 1992 to 1997 in six European countries. A comparison of 90th percentile concentrations pooled by station types across all regions showed that concentrations in marinas ( 316 ng/l) were higher than in estuaries and coastal waters (41 and 19 ng/l, respectively). A 90th percentile of 133 ng/l was reported for all pooled s tations. Temporal trends showed that Irgarol concentrations typically peake d in early summer after launching of small boats with much lower concentrat ions occurring during the spring, fall, and winter. Toxicity data used for this risk assessment were derived primarily from unpublished studies submit ted to regulatory agencies. Because Irgarol is a photosynthesis-inhibiting herbicide, it is much more toxic to plants than animals. Toxicity values fo r animals (fish and invertebrates) were much greater than concentrations of Irgarol reported in the environment. Therefore, a conservative approach us ing a distribution of only plant toxicity data (EC50s for plant growth) was used to derive a 10th percentile of 136 ng/l. This plant toxicity benchmar k of 136 ng/l was used for risk characterization. Results from probabilisti c analysis showed that ecological risk from Irgarol exposure was low in est uaries, coastal areas, and various open-type marinas. However, 10% or more of the plant species in enclosed marinas with low flushing rates may be exp osed to Irgarol concentrations that would reduce photosynthesis activity an d growth during the summer. Ecological risk to these sensitive plant specie s in enclosed marinas will likely be moderated because of the reversibility of Irgarol's inhibition of photosynthesis and the rapid recovery potential of plant communities. The ecological significance of marinas that generall y contain numerous stressors such as trace metals, tributyltin, petroleum h ydrocarbons, high nutrient concentrations, and low dissolved oxygen concent rations is a management issue that needs to be addressed.