Abstract
We examined a method of assessing the risk of lead solder in Tokyo Bay using a numerical model. The targeted metals were Pb, Ag and Cu, which constituted lead solder or lead-free solder. The ambient concentration of lead was estimated using AIST-RAMTB（Aist-The Risk Assessment Model for Tokyo Bay）, considering the atmosphere and 7major rivers as the sources supplying lead. The giant Pacific oyster（Crassostrea gigas）was selected to evaluate the extinction risk, where the EC50（growth inhibition, 380μg L－1）was used for Pb. Simultaneously, Ag and Cu were evaluated similarly based on the lethal concentration （LC50）：100μg L－1 for Ag and560μg L－1 for Cu. Uncertainty factor（UF）was defined as10. The results show the maximum risk values of5．57×10－6（where risk has no unit）for Pb, 1．40×10－6 for Ag and4．09×10－8 for Cu. It is suggested that the risk of solder lead was reduced by changing the lead solder to lead-free solder in Tokyo Bay.
