Lead in prehistoric, historic and contemporary Japanese: stable isotopic study by ICP mass spectrometry

Abstract

Lead concentration and isotopic composition of prehistoric (middle and latest Jomon era, 2000–4500 BP, n=6), historic ( Edo era, 130–400 BP, n=10), and contemporary (died in 1987–88, n=15) Japanese bones, and deciduous teeth from contemporary Japanese children born during 1985–88 ( n=17) were analyzed by inductively coupled plasma mass spectrometry. Lead concentration was lowest in Jomon bones and was higher in rural Edo, contemporary, and urban Edo, in that order. Elevated Pb concentration in historic Edo people, as reported previously, was reconfirmed. The average isotopic ratios ( 207Pb/ 206Pb and 208Pb/ 206Pb) in excavated (prehistoric and historic) bones, contemporary bones, and deciduous teeth were different from each other. The contemporary bones had the least radiogenic composition (mean 207Pb/ 206Pb: 0.879; mean 208Pb/ 206Pb: 2.126) while the excavated bones the most (0.848; 2.098), and teeth intermediate (0.866; 2.111). The comparison with the literature data of isotopic compositions of environmental samples showed that the isotopic composition of the excavated bones was within the range of Japanese ores, rocks and soils, indicating the absence of foreign Pb sources in preindustrialized Japan. That of the contemporary bones was closer to the average gasoline Pb, the use of which had been banned in the late 1970s, than to the Pb in airborne particulate matter or refuse incineration ash of 1980s. The average Pb isotopic ratios in the deciduous teeth was close to the isotopic ratios of Pb in airborne particulate matter and refuse incineration ash. These data indicated that the contemporary Japanese population was exposed to foreign Pb which had different isotopic composition from domestic Pb. Exposure to Pb of foreign origin was particularly evidently recorded in people born before the leaded gasoline ban. The history of human Pb contamination in Japan is discussed based on the present results and other previously published data.