Abstract 208 – Japanese black bears are highly exposed to lead (Pb)

Koji Yamazaki, Mayumi Ishizuka, Shota Nakayama, Nelly Banda, Shinsuke Koike,
Yusuke Goto, Kozo Yamazaki, Yui Nemoto, Boris Fuchs, Jon M. Arnemo

We collected blood samples from a total of 57 Asian black bears (Ursus thibetanus) that were
live-trapped in two study areas. The Okutama Mountains are situated in the suburbs of Tokyo, a
mega-city where the use of leaded gasoline was permitted until 1980s. The Ashio-Nikko
Mountains are located near an old copper mine and smelter. In both areas, extensive sika deer
(Cervus nippon) and wild boar (Sus scrofa) control programs and sport hunting using lead (Pb)
ammunition have been ongoing for decades.
We found that blood Pb concentrations (mean±SD) were higher in the Ashio-Nikko Mountains
(107.62 ± 29.94 µg/L) compared to the Okutama Mountains (54.27 ± 35.65 µg/L).
Pb levels of females with lactation were higher than other sex categories, and the increase in Pb
levels was associated with a significant decrease in blood lymphocyte and monocyte counts. In
bears sampled over multiple years, Pb levels showed an increasing trend.
Bears in central Japan are known to scavenge on carcasses and hunting remains of sika deer
and other large-sized mammals. Pb from spent ammunition may constitute a significant
portion of Pb exposure in the bears in both areas. In the Ashio-Nikko Mountains mining
activities are likely a major source of environmental Pb, whereas the Okutama Mountains are
more contaminated by Pb from leaded gasoline.