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MERCURY, which is known to damage the nervous system and disrupt mental
development, can also cause infertility in men at levels well below those the
WHO says are safe.

Mike Dickman, a biologist at the University of Hong Kong, and Clement Leung
of the In Vitro Fertilisation Centre in Hong Kong measured mercury levels in men
with fertility problems. They found that the hair of men with slow, deformed or
sparse sperm contained on average 40 per cent more mercury than that of men with
normal sperm. At any given age, men with 3.7 parts per million or more of
mercury in their hair were twice as likely to be subfertile as men with 2 ppm or
less. The WHO’s safety limit is 10 ppm.

Acute mercury poisoning is known to harm sperm formation in mice and monkeys.
But this is the first clear association between reduced fertility in men and
environmental exposure to mercury. The results will be published in The
Science of the Total Environment in June.

The men got their mercury from seafood, says Dickman. Volcanoes and
coal-fired power stations release the metal into the environment. It is
converted to methyl mercury by marine bacteria and taken up by fish. “Men in
Hong Kong who eat four or more seafood meals per week have significantly more
mercury than those who eat less,” he says.

The authors say the WHO’s recommended safe level for mercury in food of 0.5
ppm is too high for places such as Hong Kong where people eat lots of seafood.
Last year, the US Environmental Protection Agency estimated that at least 170
000 people in the US receive higher doses than the WHO recommends.