HONG KONG - Studies of Hong Kong men experiencing fertility problems
suggest there is a link between mercury contamination and human ability
to reproduce.
Researchers from the Hong Kong Invitrofertilisation Centre and the
University of Hong Kong (HKU) found that mercury levels are higher
in
men suffering from fertility problems than those who are not and noted
that
mercury-tainted seafood is the main source of contamination.
''These observations support the hypothesis that subfertility in human
males may be associated with mercury ingestion from seafood," states
the report, which was written by Prof Mike Dickman of HKU's Department
of Ecology and Biodiversity and two doctors from the fertility clinic,
CKM
Leung and MKH Leong. Mercury is also widely recognised as a dangerous
neurotoxin, can lead to Minamata Disease in those who ingest too much.
One of the Hong Kong study's most important conclusions is that the
standards set by the World Health Organisation (WHO) for mercury levels
in food are not appropriate for Hong Kong, or other areas where a great
deal of seafood is eaten, and should be lowered. The study was a
relatively small one - it examined mercury levels in the hair of 35
females and 166 males attending the clinic - and the results are not
conclusive,
notes Dickman.
''There is strong circumstantial evidence that mercury-contaminated
seafood has an impact on male fertility," says Dickman, who received
a
research grant from the Hong Kong Environmental and Conservation Fund
to
carry out a study of mercury levels in Hong Kong fish. ''But what isn't
clear is whether some other toxic contaminant could be affecting fertility."
Mercury contamination has also become a growing problem in the Gulf
of
Thailand, in part through discharges from natural gas producers, but
almost certainly added to by discharges from factories on the Eastern
Seaboard.
The Hong Kong study divided the men into three groups: those in the
group with the highest levels of mercury in their hair were twice as
likely to be subfertile as males in the group with the lowest levels.
Hair mercury content is considered the most reliable way to measure
contamination in humans, according to Dickman.
''Mercury in the hair of 117 subfertile males in Hong Kong was
significantly higher than its level in the hair of 42 fertile males,"
the report states. ''Although other studies reported that mercury can
alter
human [sperm-making ability], data collected in this study are insufficient
to permit us to conclude that mercury was the cause of subfertility
in
the 117 individuals reported on here."
The main source of contamination is believed to be ingestion of
seafood. ''Seafood is the major source of mercury in the diet of Hong
Kong individuals," the report asserts. ''Vegetarians who live in Hong
Kong
and who have not consumed any seafood for the last five years or more
had
very low levels of mercury in the hair [0.38 parts per million versus
3.33 ppm for non-vegetarians in Hong Kong]."
Much of the fish eaten in Hong Kong originates in the Philippines and
Indonesia, says Dickman. Studies suggest that mercury contamination
in
Victoria Harbour may be even worse, he adds, but the fish there are
often caught when they are much younger, so they have not had time
to
accumulate much of the heavy metals.
The situation sounds eerily similar to Thailand, which also imports
much of its seafood from Indonesia and the Philippines, and has serious
mercury problems of its own in the Gulf of Thailand.
Michael Chiu, assistant director in charge of water and waste policy
for Hong Kong's Environmental Protection Department, said he was not
familiar with the HKU study, and promised to look into it. But he noted
that another source of mercury contamination could be from Chinese
medicines
and shampoos.
Dickman agreed that some Chinese medicines do use mercury. He said
those being tested were asked whether they had taken herbal medicines
and they replied that they had not. But he also noted that in such
cases
patients may not have correctly answered the doctor.
Still, the report states that, ''In our opinion, the WHO guideline for
maximum mercury concentrations allowed in foodstuffs [0.5 parts per
million] is too high for parts of the world like Hong Kong where seafood
is a dietary source of protein."
The report notes that the standard should be set so that mercury
intake rates match rates of excretion, but that does not appear to
be
the case in Hong Kong because older individuals have significantly
higher
levels of mercury in their hair than those who are younger. ''Were
mercury guidelines adopted in Hong Kong similar to those adopted in
Japan, 0.3
parts per million, then the rate of mercury accumulating in humans
in
Hong Kong would likely decline," the report concludes.