Environment / Pollution

We didn't really believe the stories until we went out ourselves," Bart Mansi says. "That's when it really hit us." Last fall, he and other lobstermen along the Connecticut shore kept hearing about a great lobster die-off 30 miles to the west - one that began around the time that New York City started spraying malathion to prevent an epidemic of West Nile encephalitis. Then in early October, as they plowed into the frigid waters of Long Island Sound, they found disastrous proof of the rumors: pot after pot of dead lobsters, and others so weak they died a day or two after arriving on land.

Worried and baffled, Mansi hooked up with biologist Mike Loughlin, now at the National Marine Fisheries Service. During the next couple of weeks, Loughlin examined dead lobsters up and down the coast and took hundreds of blood samples. His diagnosis: The lobsters were killed by paramoebic and bacterial infections, but only because something had broken down the animals' immune systems first. Altogether, some 10 million pounds of lobsters died of unnatural causes off the Connecticut and New York shores last season, and the losses are expected to continue for several years.

Suggestive, disturbing, and maddeningly inconclusive, the lobster fatalities typify the environmental incidents that observers have linked to malathion. The lobstermen quickly blamed the pesticide, but sewage runoff and other pesticides could just as easily have been the culprits. True, the timing of the die-off was suspicious—malathion has been known to kill crustaceans, and the spraying had already killed hundreds of fish on Staten Island. But it’s hard to imagine that, after being diluted in millions of gallons of water, enough of the pesticide could have drifted or flowed into the Sound to kill the lobsters.

As for the pesticide’s effect on people, the evidence is just as ambiguous. Biologists say that the human body can break down malathion much faster than mosquitoes can, and most agree that the spraying in New York was too light to cause harm. Yet U.S. Poison Control Centers have a database of more than 10,000 incidents involving malathion, some of them fatal. This spring, after a four-year review, the EPA declared that there is “suggestive evidence” that malathion can cause cancer. Yet an agency representative described the danger as “below our level of concern.”

How to weigh such risks? When does paranoia become reasonable suspicion? When does the long-term danger of spraying a mild neurotoxin outweigh the short-term danger of a crop infestation or a mosquito-borne disease? This summer, city officials across America may ask themselves those questions as they face the same agonizing choice that New Yorkers faced. West Nile encephalitis—a cousin to St. Louis encephalitis—was never seen in North America before last year and is probably here to stay, most epidemiologists say. The next likely target is the Southeast, with its sweltering temperatures and plentiful mosquitoes, but no one knows when an epidemic will come or what toll it will take. In 1975, when St. Louis encephalitis struck Chicago, more than 500 people contracted the disease and 47 died; the next year only a handful were infected.

Last year, when New Yorkers began dying of the disease, the city ordered a fleet of helicopters, trucks, and an airplane to spray malathion and other pesticides for weeks. The potential epidemic was eventually contained (with the help of cold fall temperatures), but the long-term costs of the victory may never be known. This year, the city isn’t taking any chances. In March, mosquitoes in Queens were found to contain West Nile viral RNA, so the city launched an unprecedented campaign to keep mosquitoes from breeding and hatching. Spraying pesticides like malathion, officials say, will remain an option.

In the meantime, hardware stores still sell malathion, and the EPA can only assure that it’s “one of the least risky of the riskiest class of pesticides.” Before health officials decide to spray it over cities again, perhaps they ought to take a look at malathion’s less-than-reassuring history (see “Malathion: Fear by Year,” at left)—remembering that DDT, too, once seemed like humanity’s last, best defense against mosquito-borne diseases. Better yet, as temperatures rise and a faint buzzing begins to fill the air, officials might want to go talk to a few lobstermen. “We’re holding on by a couple of shoestrings,” Bart Mansi says. “Females with eggs were killed, as well as juveniles, so we could be looking at a seven- to 10-year cycle with a serious downturn. The guys farther west, closer to New York— somewhere around 99 percent of their catch is dead, so they’re not even going out any more. And the people that sprayed this stuff are pretending nothing’s happened.”