by Dr. Iain Corness
There has been some interest in the
popular press about Thai ladies and mercury. The most used cosmetics in
Thailand are whitening creams, and many skin whiteners contain mercury, even
though this substance is banned.
Mercury works by blocking the production of skin-coloring melanin - but it
also has nasty side effects. Mercury and mercurial compounds can be absorbed
into the body by inhalation of the vapors, ingestion, or skin contact. As a
poison, the damaging effects of mercury are subtle and cumulative, building
up over time.
When absorbed, mercury has been discovered in blood, urine, bile, sweat,
saliva, and milk. It has also been discovered in the brain, bones, the
cellular tissue, in serous membranes, in the parts close to the joints, and
in the lungs and liver.
The symptoms of mercury poisoning include emotional disturbances,
unsteadiness, inflammation of the mouth and gums, general fatigue, memory
loss, forgetfulness and headaches. Excess mercury in the system has been
known to cause kidney problems (membranous nephropathy).
Despite legislation, research by consumer groups has found in Thailand that
up to 20 percent of whitening creams are highly contaminated with mercury.
Of course, this is nothing new, nor is it just a local problem. In May 2010,
the Chicago Tribune had 50 skin-lightening creams tested at a lab (most of
the creams were bought in stores, a few were ordered online). Six were found
to contain illegal amounts of mercury. In August 2011, Philippine watchdog
group EcoWaste Coalition conducted a test of 12 brands of whitening creams.
11 tested positive for high levels of mercury.
One reason why mercury keeps on being used is that it is effective in
lightening dark spots and stubborn pigmentation but has a high remission
rate, requiring the user to keep using the cream, before they turn dark once
However, there is another problem with mercury, and that is not an “adult”
problem, but one where mercury affects the fetus.
The effects of small doses of mercury on adults is not great, though
absorption should be avoided as much as possible, but the same cannot be
said about the effects on the fetus. It appears that the unborn is more
sensitive than the adult and subtle delays in achieving the usual milestones
result from the exposure to mercury in the womb.
One apparently contradictory problem occurs with dieticians’ recommendations
that everyone should eat a couple of portions of fish each week, but
unfortunately, it is the fish that have the mercury as the unwanted
addition. Not that the ocean bed is full of discarded mercury thermometers,
it is just that mercury is a naturally occurring chemical compound, and fish
are good at absorbing it.
The other interesting fact is that not all species of fish carry the same
body burden of mercury. The reason for this appears to be that the largest
mercury carriers are also the largest fish that live longer than the others
and are also higher up the aquatic environmental food chain than the others.
(We, of course, are even higher up the food chain, but don’t spend all day
The ones that have the largest concentrations of mercury are then
shark/flake, ray, swordfish, barramundi, gemfish, orange roughy, ling, and
southern bluefin tuna. Since tuna is one of the more popular types of canned
fish available here in Thailand, is this then a problem? Fortunately no,
because the species used in canned tuna is a smaller one and generally the
fish are only about one year old when caught for canning.
So what can pregnant ladies do, or even those contemplating pregnancy? Can
you get rid of the mercury by careful cooking of these types of high mercury
bearing fish? Unfortunately no. No matter how you cook your fish (or
shellfish) it does not change the levels. The simple answer is that you
should stick to the smaller fish species, even if bluefin tuna steaks are
your kind of seafood.
And even though the absorption of mercury from the whitening creams is
possible, the body burden of mercury from this is probably not very high at
all, so caution is probably all that is needed. And read the label.