Unfounded Fears Cloud Truth About Mercury : Contrary to popular opinion, the silvery liquid metal known as quicksilver is not poisonous. Ignorance about the substance is needlessly terrorizing society.

High school students were recently found playing with droplets of mercury. The authorities called in a team of environmental specialists in protective white suits and sent 17 children to a hospital. Doctors found nothing wrong with them.

The Jan. 26 incident at Verdugo Hills High School in Tujunga was hardly the first overreaction based on the fear of mercury, or the most bizarre.

Some time ago in a local hospital, a staff person dropped and broke an ordinary fever thermometer in a ward hallway. The mercury disappeared into the interstices of the floor, but no matter, it was still considered an emergency. The staff was evacuated from the hall, and in came the poison fighters in the white suits.

Several years ago, many people had silver fillings removed from their teeth because they thought they were being poisoned by the mercury used to soften the silver. The flap was started by scare TV reports of highly uncritical experiments. Serious study revealed no ground for the fear, which has greatly diminished but has not disappeared.

Is mercury, the silvery liquid metal called quicksilver, which is so hard to hold, poisonous? No, it is not.

The fact that mercury’s naked presence in a room is now regularly treated as an emergency does not just reflect widespread ignorance of its properties. It also reflects the fact that we are living in the most terrified society in the world--as well as the healthiest.

Poisoning from vapors given off by mercury metal can occur in workers accidentally exposed to large amounts of mercury heated to several hundred degrees, as in mercury boiler generators.

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An early cause of poisoning was the mining of gold and silver. Powdered ore was soaked in hundreds of pounds of mercury, which dissolves these metals. The mercury was then heated to about 550 degrees Fahrenheit and boiled away, leaving a spongy mass of gold or silver and releasing large amounts of hot, toxic mercury vapor. This process disappeared in the 19th Century.

We need not fear the mercury in thermometers, silent switches or even in small puddles on the floor, for at room temperature, the amount of vapor given off by mercury is very small. Nor need we fear the amalgams used to fill teeth. In no case is there significant vapor at room or body temperature.

The main cause of the terror about mercury is the failure to differentiate between mercury metal and its compounds. Under laboratory conditions, mercury can be compounded with acids to make mercury salts or with carbon compounds to make organic mercury. In these forms mercury is usually very toxic. The salt with two chlorine atoms, bichloride of mercury, was used earlier in this century to sterilize diapers. It was known to be dangerous and was sold in blue, coffin-shaped tablets. At the same time, the mercury compound with only one chlorine atom, called calomel, was only minimally toxic and was regularly prescribed as a strong cathartic (it is no longer so used).

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The major public information about the poisonous nature of mercury came from the Minamata fish poisoning in Japan. A chemical factory dumped organic mercury waste into Minamata Bay for about 50 years. The small organisms that the fish ate accumulated the poison in their protein, which further concentrated in the protein tissues of the fish, which were eaten by people around the bay.

There was not a great deal of mercury in the water, but the food chain concentrated the poison. The disease was so characteristic that it was named Minamata Disease. It was basically a poisoning with methyl mercury, a particularly toxic organic mercury compound. In general, we do not encounter it except in certain chemical wastes, which have been identified and must be purified before entering the environment.

Many organic mercury compounds can be absorbed through the skin, but not all. Remember the days when our minor cuts and abrasions were daubed with Mercurochrome? This is an organic compound of mercury that is not absorbed through the skin. (It is very toxic if ingested, however).

Misapprehensions about mercury have worked themselves into apparently authoritative reference books. “The Condensed Chemical Dictionary,” for example, says metallic mercury is “highly toxic by skin absorption” and calls spillage a potential toxic hazard. Both those statements are simply untrue except in the presence of extremely high temperature. A person with mercury on the skin at even 212 degrees--far below mercury’s boiling point--would have more to worry about than the mercury.

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Since writers on environmental hazards tend to overemphasize the toxicity of most things, the public can hardly be faulted for shouting alarms even if there are none. I have great sympathy for the firefighters who are required to interpret toxicity rules, which, in many cases, seem to imply that if a large amount of something is bad, then even a tiny amount is also bad, and that if one of two substances with similar names is toxic, the other must be too.

Don’t worry about quicksilver.