We measured Pb/Ca and Pb isotopes with high resolution in the high-Mg calcite skeleton of a Pacific sclerosponge (Acanthochaetetes wellsi) collected from the reef edge off the western coast of Kume Island (East China Sea), to investigate its potential to be used as a proxy for lead contamination in the environment, and atmospheric transportation and fallout over the last few decades. Skeletal Pb/Ca ranged from 58 to 1642 nmol/mol, 10× higher than that of the aragonite skeleton of Pacific corals, and 2.5× higher than that of the aragonite skeletons of Caribbean sclerosponges. The Pb/Ca timeseries recorded from 1967 through 2007 CE correspond to historical changes in atmospheric lead flux in anthropogenic aerosols. Pb isotopes (206Pb/207Pb and 208Pb/207Pb) in the sclerosponge skeleton document that the main source of lead emissions shifted from Japan (1970–1980 CE) to China (1995–2005 CE), as expected from the timing of legislation against the use of leaded gasoline in Japan and China. Our results indicate that the skeleton of the Pacific sclerosponge is a powerful proxy to monitor environmental lead pollution. Applying this methodology to long-living and/or fossil specimens could be useful in determining the interannual variability of atmospheric transport and dynamics over geologic time scales.