Survey for the occurrence of the new antifouling compound Irgarol 1051 in the aquatic environment

Irgarol 1051, (2-methylthio-4-tert-butylamino-6-cyclopropylamino-s-triazine), is a newly developed herbicidal additive for use in copper-based antifouling paints. It is intended as replacement for the highly toxic antifouling agent tributyltin, which has been regulated internationally. Currently, there is no information in the open literature on its environmental occurrence outside Europe. A two-year survey was conducted in 1996–1997 to investigate the occurrence of Irgarol 1051 in Canadian and Japanese aquatic environments. Six large trade ports (Vancouver, Toronto, Montreal, Halifax, Mizushima and Kobe), 73 marinas and 13 fishery harbors were surveyed. Irgarol 1051 was not detected in the Canadian aquatic environment, but was positively identified in the enclosed coastal waters of the Seto Inland Sea in Japan. Among the six trade ports surveyed, only the Mizushima Port had low levels of Irgarol 1051, up to 19.5 ng/L. Approximately 27% of the marinas surveyed in the Seto Inland Sea were found to have been contaminated by Irgarol 1051, ranging in concentration between 12.5 and 264.2 ng/L. Irgarol 1051 was found more frequently in fishery harbors than in marinas, indicating that besides marinas and trade ports, fishery harbors can also be a significant source of contamination for the aquatic environment. Survey for Irgarol 1051 in the fishery harbors has not been reported before, and it is suggested that fishery harbors, in addition to ports and marinas, should be included in the survey list during the Irgarol 1051 monitoring study. Irgarol 1051 has been reported to be highly toxic to nontarget marine algae with the observable growth inhibition at a concentration as low as 50 ng/L, which is well within the ambient concentration levels found in some localities of the Seto Inland Sea.