Jeff Green | Jan 19, 2006
Feature Article - January 19, 2006
Feature ArticleJanuary 19, 2006
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Better to eat Perch than Pickerel
Commentary by Gray Merriam
People in Brazil who live downstream from gold mines and forest clear cuts have too much mercury in their bodies. Mercury is especially bad for unborn children. It can affect their mental development. It has similar effects on older people, allowing early dementia.
In most lakes there is less than one nannogram (one part per trillion) of mercury and only about 1% of that is the really dangerous methyl mercury that we absorb readily.
But that little bit of methyl mercury is increased in concentration as it moves from the water into fish foods and then into fish and from that fish into the predator fish that eats it. The concentration can increase so much that the mercury in the predator fish can be one million times as much as the mercury in the water that the fish swims in (“biomagnification”).
The mercury level in the fish that are eaten by those folks in Brazil is about the same as the level in our game fish here. The reason that it is such a health problem for those Brazilians is that they eat fish at least twice each day. We should not. And we should eat fish that don’t eat other fish as pike and pickerel do. Instead, if we eat fish that feed on invertebrate fish food, we remove one step in that chain of biomagnification. It also reduces the amount of mercury in the fish we eat if we eat smaller fish that have been accumulating mercury for a shorter time. Small fish are better for you than trophy-size.
Health Canada’s suggestions amount to about one-quarter pound every three days of large predatory fish. In an attempt to protect vulnerable populations such as the unborn and the elderly, the suggestion by the U.S. Environmental Protection Agency allows only about one-quarter as much as the Health Canada guideline.
Mercury in our fish comes from several possible sources: mining and smelting, coal-fired power plants, damming of rivers and lakes, the effects of acid rain on lake beds and some municipal incinerators top the list.
Although programs are in place to reduce those sources, progress is likely to be slow (consider the replacement of Ontario’s coal-fired power plants). More telling, we have already released so much mercury into our environments and our dams that there will be a constant supply of mercury being turned into methyl mercury and taken up into the food chains for a very long time.
You should probably follow the suggestions about how much fish to eat well into the future. You can learn more about the amount of fish that you should eat from any Ontario Lake in "Guide to Eating Ontario Sport Fish", 2005-2006 edition, a free publication from the Queen' Printer of Ontario available from MNR offices and elsewhere.