By The Associated Press

DDT is one of the most potent man-made bombs ever to explode in the insect world.

It has probably saved hundreds of thousands of human lives by wiping out the mosquitoes that transmit malaria. It has probably saved millions of dollars of crops from being consumed by insects.

Yesterday's announcement by the government that the insecticide will be all but banned within two years underscores the fact that modern technology can often do as much harm as good.

In Borneo, for example, the World Health Organization once used DDT to kill malaria-carrying mosquitoes. The insecticide killed the mosquitoes but did not kill roaches, which accumulate DDT in their bodies. Long-tailed lizards, called geckoes, which roam the walls and floors of tropical houses, ate the roaches.

Lizards Slowed Down
The DDT from the roaches reached the nervous system of the lizards. The lizards slowed down and became less agile; cats caught them easily and ate them. The cats died from the DDT in lizards.

Rats started moving in from the forests, carrying the threat of an epidemic of plague. So cats were parachuted into the villages to catch or drive away the rats. They did.

Then the roofs of the houses started caving in; the lizards had also been eating caterpillars that made their meals from the roof thatching.

This story is told be LaMont C. Cole, an ecologist at Cornell University.

DDT is but one example of a technological blessing with a price tag that is often unknown or unpredictable at the outset.

Just as the automobile makes a society mobile, it also kills 50,000 Americans annually and contributes to smog. Penicillin saves lives, yet kills some people sensitized to it.

DDT - dichloro diphenyl trichloroethane - is one of a family of chemicals developed after World War II. It is lethal to a wide range of insects. Among its uses were attempts to control the beetle that causes Dutch elm disease, and the lice that spread typhus. Against the malaria mosquito, it performed well.

However, it is not easily broken down by chemical actions of living things. It persists in water and is carried by the air.

Penguins in Antarctica have DDT in their bodies, and it is stored in the fatty tissues of humans. While there is no proof that it has caused human deaths, it is blamed for wiping out great populations of birds and fish.

More than a decade ago, DDT was being called a potential human nerve poison. But United States Public Health Service scientists reported that human volunteers had eaten daily for a month about 200 times more DDT than the total found in foodstuffs and had not shown any harmful effects.