Toxicity and Environmental Risk Assessment of Polycarbamate and Its Main Components to Marine Algae and Crustaceans

Polycarbamate is commonly used as an antifoulant coating on fishing nets in Japan. Although its toxicity to freshwater organisms has been reported, its toxicity to marine organisms is currently unknown. We conducted algal growth inhibition and crustacean immobilization tests to assess the effects of polycarbamate on marine organisms. We also evaluated the acute toxicity of the main components of polycarbamate, namely, dimethyldithiocarbamate and ethylenebisdithiocarbamate, to algae, which are the most sensitive tested organisms to polycarbamate. The toxicities of dimethyldithiocarbamate and ethylenebisdithiocarbamate partially explain that of polycarbamate. To assess the primary risk, we derived the predicted no-effect concentration (PNEC) for polycarbamate in a probabilistic manner using species sensitivity distributions. The 72 h no observed effect concentration (NOEC) of polycarbamate to the alga Skeletonema marinoi-dohrnii complex was 0.45 μg/L. The toxicity of dimethyldithiocarbamate may have contributed up to 72% of the toxicity observed for polycarbamate. The fifth percentile of hazardous concentration (HC₅) derived from the acute toxicity values was 0.48 μg/L. Comparison of previously reported environmental polycarbamate concentrations in Hiroshima Bay, Japan, to the PNEC estimated using the minimum NOEC and HC₅ suggest that polycarbamate currently poses a high ecological risk. Therefore, reducing the risk by restricting polycarbamate use is necessary.