• U.S.

Environment: The Bug as Garbage Man

4 minute read

It is no secret that U.S. waters contain noxious substances like DDT, lead and mercury. The mystery is how to remove them. The pollutants are dissolved in such microscopic particles that they cannot be sifted or scooped out by chemical or mechanical means.

Researchers have lately pondered the fact that aquatic organisms (fish, plankton, diatoms, insect larvae) concentrate the dissolved pollutants in their bodies. That fact led Robert Metcalf, head of the University of Illinois’ zoology department, to a fascinating idea: Why not use certain insects to sop up the pollutants?

Breaking the Cycle. In a report to the Entomological Society of America, Metcalf pointed out that mosquitoes, May flies, midges and stone flies spend a great part of their lives as larvae in the water before metamorphosing into their more familiar buzzing selves. In a controlled experiment, Metcalf built a small tank to duplicate the ecosystem of a lake and its shore. He discovered that adult mosquitoes leaving the tank contained concentrations of DDT 100,000 times as strong as could be found in the water itself.

Left to die a natural death, the insects would decompose and the next rain would wash their internal cargo of long-lived pesticides and toxic metals back into the water supply. But Metcalf proposes breaking the natural cycle. Since the insects are attracted to light, they can easily be caught in standard, electrically illuminated traps. One night Metcalf captured 300,000 adult midges in a single trap. They can then be burned at high enough temperatures to break down the pesticides.

Metcalf estimates that Lake Michigan contains 10,000 Ibs. of dissolved DDT. About 50 trillion insects leave the lake annually, each one containing .0000001 gram of the pesticide. If 10% of the bugs were trapped and burned every year−and no more DDT was sprayed around the watershed−the lake could be free of the pesticide in a decade.

Oil Eaters. Other scientists are trying to make use of the long-known fact that some bacteria “eat” oil. Can this be applied to oil spills at sea? Though well-funded research projects are under way at such famous oceanographic centers as Rutgers University and Florida State University, the most promising results have come from a small, modestly financed firm in Springfield, Va. Going beyond most other researchers, Bioteknika International Inc. has produced a special microbe “cocktail” that seems to break oil down into carbon dioxide, water, sugars and proteins−all of which enhance marine life.

The cocktail is one man’s response to the Torrey Canyon spill off England in 1967. Appalled by the damage ($31.5 million) and the inadequate methods used to deal with it (detergents, napalm), Microbiologist Edward N. Azarowicz sought organisms that can eat all the chemicals in oil. No business or government agency would back him. As a result, Azarowicz quit his job at Atlantic Research Corp. in 1968 to devote full time to microbe hunting. With $2,000 of his own and a little help from his scientist friends, he found 19 kinds of land-based microbes that he calls “oil-eager eaters.” He mixes these with one species of sea microbe, plus special proteins to give the bacteria a “running start” on crude oil. Tested recently on experimental oil spills in Chesapeake Bay and the Potomac River, the bugs devoured 100-sq.-ft. layers of oil in four days. Cost: between $1 and $2 per gallon of oil−about half the cost of using less effective detergents.

In a few months Bioteknika will start making freeze-dried pellets of the basic bacterial cocktail (different kinds of oil need slightly different mixtures). The product can be flown to the site of an oil spill and simply dropped onto it. Once the microbes hit the water, they return to voracious life. When all the oil is gone, they quickly starve to death. Their remains then become safe food for other forms of life.

More Must-Reads from TIME

Contact us at letters@time.com