Ecological Risk Assessment for Irgarol 1051 and Its Major Metabolite in United States Surface Waters

The objective of this study was to determine the ecological risk of the antifoulant Irgarol 1051 and its major metabolite (GS26575) in United States surface waters by using a probabilistic approach. Distributions of environmental exposure data were compared with the distribution of species response data from laboratory studies to quantify the likelihood and significance of ecological risk. Water monitoring data from both the Chesapeake Bay (2001) and southeast Florida (1999–2001) were used to characterize exposure. Toxicity testing has demonstrated that plants are much more sensitive to Irgarol and GS26575 than animals; therefore, the conservative effects benchmark used to characterize risk was the plant 10th centile for both Irgarol (251 ng/L) and GS26575 (12,500 ng/L). Ecological risk from Irgarol exposure in Chesapeake Bay marinas, a river, and a mainstem area was generally low with the possible exception of the Port Annapolis marina in Annapolis, Maryland. This enclosed marina has a high density of boats, a low flushing rate, and has historically been reported as a “worst case scenario” for other antifoulants such as tributyltin. Ecological risk from GS26575 exposure at Chesapeake Bay sites was judged to be very low as all environmental concentrations were an order of magnitude below the effects threshold for plants. Ecological risk from Irgarol exposure in southeast Florida surface waters was found to be low at various marina, port, river, bay/embayment, channel, and ocean areas. Even the highest Irgarol concentration reported in southeast Florida waters (182 ng/L) was less than the conservative Irgarol effects benchmark of 251 ng/L (plant 10th centile). Ecological risk from GS26575 exposure in southeast Florida waters was also very low.