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[Lead content of bones excavated from archaeological sites in Hokkaido].

OBJECTIVES
The lead content of excavated bone samples from archaeological sites in Hokkaido was measured to obtain insight into the source of human lead contamination known in the historic Japanese Edo era.


METHODS
Fifty-seven rib samples excavated from 11 sites of five different eras in Hokkaido were analyzed for lead (Pb), calcium (Ca), and iron (Fe) contents by ICP mass spectrometry and ICP emission spectrometry.


RESULTS
The Pb/Ca ratio (mg Pb/kg Ca) was low (approximately 2.0) and constant from the Jomon (approximately 5000 BP) to the Satsumon (approximately 750 BP) eras; however, its median increased to 11 in the Modern era. This elevation of Pb/Ca ratio in the bone samples from sites of the Modern era was not considered to be due to a greater bone contamination with soil particles because of similar Fe concentrations in the bone samples from this era to those in other eras. This historic trend of Pb/Ca ratio was similar to that observed in other parts of Japan. The elevated Pb/Ca ratio in the bone samples excavated from sites in the Modern era in other parts of Japan, that is, Edo era, has been ascribed to the usage of face powder containing Pb; however, people inhabiting Hokkaido in those days, the Ainu, were not considered to have the custom of using face powder.


CONCLUSIONS
Contamination source(s) other than face powder was postulated in the Modern era of both Hokkaido and other parts of Japan.