In order to investigate the body burden levels of toxic metals in Japanese, five toxic metal concentrations in
scalp hair samples from 28,424 subjects from infant to elderly were determined with inductively coupled plasma mass
spectrometry (ICP-MS). The geometric mean of hair mercury concentrations showed a high-significant age-correlated increase
(r = 0.341, p < 0.0001) with a peak at the 6th decade of life and then decreased with further aging in both sexes. The
mean mercury concentrations in male adults were significantly higher than those in female (p < 0.001), indicating the
gender difference (male > female) in mercury accumulation. Arsenic also showed a similar accumulation profile with agedependency
and gender difference in adult subjects. In contrast, cadmium, lead and aluminium exhibited another type of
accumulation profile: the highest burden level was observed in infants aged 0-3 years old for every element in both sexes.
In addition, cadmium was found to have a character accumulating in aged females, with significant age-dependency (r =
0.134, p < 0.0001) and gender difference (female > male).
These findings suggest that toxic metals are classified into two families on the basis of their accumulation profiles, and
that the three elements of mercury, arsenic and cadmium which accumulate age-dependently in adults, may play a role in
aging process and higher burden with them may lead to acceleration of aging.