Fate and ecotoxicity of the new antifouling compound Irgarol 1051 in the aquatic environment

Residue analyses and ecotoxicity assessment were conducted on the new antif ouling compound Irgarol 1051 (2-methylthio-4-tert-butylamino-6-cyclopropyla mino-s-triazine) and its degradation product M1 (2-methylthio-4-tert-butyla mino-6-amino-s-triazine) in order to delineate the environmental fate and i mpact of Irgarol 1051 on the aquatic ecosystem. For the first time, the Irg arol degradation product (M1) was positively identified in environmental sa mples. During the 1998 Irgarol survey, concentrations of M1 (up to 1870 ng/ l) were generally higher than those of Irgarol in the coastal waters of the Seto Inland Sea in Japan, suggesting a greater environmental persistence f or M1 than for the parent compound Irgarol 1051 in the aquatic ecosystem. E cotoxicity testing revealed that Irgarol 1051 and M1 were moderately toxic to a marine bacterium and the four crustaceans tested, but were highly toxi c to some algae and higher plants. In the root elongation inhibition bioass ay, M1 showed a phytotoxicity at least 10 times greater than that of Irgaro l and six other triazine herbicides (terbutryn, terbutylazine, terbumeton, simetryn, atrazine and simazine). These results strongly suggest that both Irgarol 1051 and its persistent degradation product M1 may potentially affe ct and/or damage the primary producer community in aquatic ecosystems. To s afeguard the aquatic ecosystem from the damaging impact of micro contaminan ts, it is recommended that, besides monitoring for the target parent compou nd, major degradation products should also be included in environmental sur veys. Otherwise, then is a risk of underestimating the ultimate impact of a particular toxicant on the environment. (C) 2000 Elsevier Science Ltd. All rights reserved.