Douglas . Rowland, age 9, of Latham, New York, for his question¬:
How does mercury get into fish?
Mercury is harmful to living things. It has been here since the world began ¬but the earth had it buried in rusty red rocks and other minerals. Ages ago, people learned to seperate it from its mineral ores. They admired the slippery, silvery metal and later they used it to make useful thermometers. Then the modern Age of Industry began. Scientists discovered many other uses for mercury. More of it was freed from the earth and used in factories. A lot of this has been dumped back into the world of nature along with other harmful pollutants.
Some scientists also love the world of nature and respect it. For years they warned us about many harmful pollutants. But until a year ago; mercury was not on the list. Of course, these thoughtful chemists knew that this silvery liquid metal is harmful to living things. They also knew that a lot of it was being used to help to manufacture dozens of modern products. Naturally, some of it escaped with various waste chemicals. These industrial wastes were dumped into streams that carry most of them to the oceans.
Until lately, the experts took it for granted that the dumped mercury would sink safely to the bottom of streams and rivers. Then a year ago, they found poisonous doses in Great Lakes fishes. Everybody was shocked. Right away, the government set dozens of research teams to work. There were two parts to the problem. First., are other food items safe? Second, how did poisonous forms of mercury get into the fish?
The government bans foods with more than five parts of mercury to a million parts. The level they allow is about ten times safer than safe. Cereals and bread, milk and potatoes and other grocery items were tested. They were safe. But fish from other lakes and certain food fish from the sea did contain poisonous forms of mercury. They were taken from the market at once, and the testing still goes on.
Meantime scientists investigated how the mercury gets into certain fishes. They need more time to explain all the details. But they now know that waste mercury does not sink safely to the bottom. In moving water it unites with other factory chemicals and forms several very poisonous mercury compounds. Some experts suspect that bitsy bacteria may help to do this deadly job. In any case, the fishes eat the mercury with their food. And those that eat smaller fishes get more concentrated doses.
In 1969, factories around Lake Erie used up 290 flasks of mercury. Last year, after they learned the danger, they used less than 20 flasks. Meantime government experts are busy testing our foods and banning the risky ones. And science teams are busy checking all possible sources of mercury pollution. When heated, the liquid metal turns to gas. Mercury vapor has been detected in the air above furnaces that burn paper, soft coal and oil. And more is added with the other fumes that come from automobiles.