[Health and environmental risk assessment of organotin pollution in Japan]

In the course of developing the Concise International Chemical Assessment Document (CICAD) on triphenyltin compounds for the IPCS, the author assessed health and environmental risks paused by major organotin species, i.e., triphenyltin compounds and tributyltin compounds. Organotin has been used widely as biocide in such applications as antifouling paints of boats and for other purposes, until its use was restricted in 1980's after discovery of severe damages on aquatic ecosystem caused by this agent. Among many other deleterious effects of organotin to aquatic species, imposex is one of the most conspicuous effects which is the development of male reproductive organs by female gastropods at concentrations as low as a few ng/l. Although environmental concentrations of organotin have declined as a result of tight regulations, periodical monitoring in these years shows their levels in the water still range several ng/l in Tokyo bay area which are hazardous to certain aquatic lives. Human intake of organotin in foods has been estimated through market basket surveys in Japan which showed intake of triphenyltin or tributyltin compound in 1997 as 2.29 micrograms/day (as tributyltin chloride) and 2.69 micrograms/day (as triphenyltin chloride), respectively. The intake value for tributyltin chloride corresponds to 5.2% of the provisional acceptable daily intake (ADI) estimated for bis(tributyltin) oxide (TBTO) in Japan, and 28.0% of the guidance value suggested in the CICAD draft for TBTO, respectively. The intake value for triphenyltin chloride corresponds to 10.8% of the ADI estimated by the FAO/WHO Joint Meeting on Pesticide Residues. Potential critical effects on human health observed in animal tests are the effects on immune systems and reproduction. Based on this investigation, needs for future research on mechanism of toxicity and further control of risks are discussed.