On the other hand, drinking water in many countries contains
lead. For example, in Bangladesh, a high level of lead
is detected in drinking water [3]. In Japan, lead piping has
been widely used, because lead is inexpensive and easy to
fabricate. This has caused lead to dissolve into tap water,
which has raised concern in society. Lead accumulates in
human bodies and causes abnormal calcium metabolism [4]
and immune disorders [5]. Fetuses and babies are particularly
vulnerable to lead-induced intelligence impairment [6].
In light of this, replacement of lead piping with polyethylene
piping has been undertaken, but the Japan Water Research
Center reported in 1999 that 8,520,000 households still use
lead pipes and the total length of lead piping amounts to
more than 27,000 km [7]. The WHO guideline for drinking
water stipulates that the lead concentration in drinking water
be less than 0.01 mg/L. In Japan, the maximum lead concentration
allowed in drinking water was changed from 0.1
to 0.05 mg/L in 1992, and it was further changed in 2003
to 0.01 mg/L, which is the same as the WHO standard.