1971
After seven months of hearings, six years of litigation, and one Nobel prize (in 1948) for medicine and physiology, DDT is banned in the United States, leaving malathion as one of its most effective replacements.
An epidemic of St. Louis encephalitis ripples across the Midwest, infecting 2,500 people in 35 states.
1976
During a malaria eradication program in Pakistan, 2,800 spray workers are poisoned by improperly stored malathion that has turned into isomalathion. Five of them die.
Two EPA-funded investigators report that malathion “may be highly toxic to target and nontarget organisms alike.” Its use is likely to grow more dangerous, they say, as pests develop resistance to it and have to be sprayed with higher concentrations.
1990
An outbreak of St. Louis encephalitis in Florida infects 223 and kills 11. Malathion and other pesticides are sprayed to contain it.
1996
Prompted by the newly minted Food Quality Protection Act, the EPA begins to review malathion’s safety, focusing on its effect on fetuses and the human endocrine and nervous systems, and its potential for causing cancer.
June 1997
State and federal agricultural agencies in Florida’s Hillsborough County begin spraying malathion to control Mediterranean fruit flies. High levels of malathion are found in the area’s waters, and the EPA tightens restrictions on spraying near bodies of water. Later, local news reporters in Florida film 55-gallon drums of malathion that have sat on the tarmac near Tampa International Airport for weeks, potentially degenerating into isomalathion. (A representative from Cheminova, the major producer of malathion, now says, “It would be extremely unlikely that you could store malathion long and hot enough to cause a problem.”) Thousands of area residents later complain of what they describe as pesticide-related headaches, sinus congestion, and respiratory problems.
1998
Malathion bait spray, mixed with corn syrup, is once again sprayed in Florida, but this time the state legislature mandates a survey to track the pesticide’s effects. Omar Shafey, an epidemiologist with the Florida Department of Health, reports 123 probable or possible cases of acute pesticide-related illness, including nausea, swollen eyelids, and shortness of breath, in four counties. He recommends that malathion bait spray no longer be used over urban areas.
A class-action suit, claiming personal and property damage to more than a million Florida residents, is filed against the malathion manufacturer Cheminova.
Dead birds appear in parks, roadsides, and suburban golf courses throughout New York City and its surroundings. Dissected, they show signs of viral infection in their hearts, livers, and spleens, as well as swollen brains with burst blood vessels.
A man arrives at Flushing Hospital Medical Center in Queens, feverish and delirious. After three days in intensive care, he can’t lift his arms or legs from the bed. Soon more patients appear with the same symptoms. Epidemiologists finger St. Louis encephalitis as the culprit.
The first New York victim of what is thought to be St. Louis encephalitis dies.
City officials send out a helicopter to spray malathion on parts of Queens and the Bronx. Mayor Rudolph Giuliani assures the public that the pesticide is safe and harmless but adds that “there is a slight chance that if you were to just breathe it in, you could get sick.” The spraying will continue for weeks. The New York Department of Health counsels the public to stay indoors and to bring all children’s toys inside, but assures that the malathion spraying should be harmless to humans.
Declaring the encephalitis epidemic over, city officials end pesticide spraying.
The Centers for Disease Control announces that West Nile encephalitis, not St. Louis encephalitis, is responsible for the deaths in New York City. First reported in 1937 in Uganda, West Nile virus travels throughout Africa, Eurasia, and the Middle East on various species of migratory birds. The birds, in turn, transmit it to mosquitoes, which transmit it to people. In Romania in 1996 and 1997, for instance, the virus infected some 500 people, killing 50. How and why the virus crossed the Atlantic is a matter of conjecture.
Hundreds of fish, poisoned by malathion, are found floating in Staten Island’s Clove and Willowbrook lakes.
March 2000
Omar Shafey is fired by the Florida State Department of Health. He later files a claim under the federal whistle-blower statute.
March 9, 2000
The Centers for Disease Control reports that overwintering mosquitoes, collected in Queens, were found to contain West Nile viral RNA.
New York City officials announce a new mosquito-control plan for New York City. Workers will clean up standing water in empty lots and tire piles, and spray larvicides on parks and sewers, using malathion and other pesticides in a “focused and judicious manner.”
After a four-year review, the EPA announces that malathion is less likely to cause cancer than once believed, but there is “suggestive evidence of carcinogenicity” and there have been “numerous” poisonings. “I suppose that one would characterize it as less risky than we thought,” says Stephen Johnson, a deputy assistant administrator at the EPA. “But no pesticide is 100 percent safe. Pesticides are intended to kill things, and malathion is part of a class of compounds that are among the riskiest on the market.”