Acute Toxicity of Pyrithione Photodegradation Products to Some Marine Organisms

We evaluated the acute toxicity of zinc pyrithione and copper pyrithione, used as antifouling booster biocides, and their six main photodegradation products to three marine organisms, representing three trophic levels: an alga (Skeletonema costatum), a crustacean (Tigriopus japonicus), and a fish (Pagrus major). The acute toxicity values of the pyrithiones for S. costatum, T. japonicus, and P. major were 1.5–1.6, 23–280 and 9.3–98.2 μg L, respectively. The acute toxicity values of photodegradation products of the pyrithiones such as 2-mercaptopyridine-N-oxide and 2,2′-dithio-bis-pyridine-N-oxide for S. costatum were similar to those of the pyrithiones. These results suggest the necessity of risk assessments for not only the pyrithiones but also their photodegradation products.