If you live in one of the 34 states where West Nile virus has been discovered, should you draw comfort from the clouds of pesticides being sprayed into the air to kill off mosquitoes?
"The chemicals have not been adequately tested for their human health effects," cautioned Dr. Sheldon Krimsky, a pesticide-risk expert at Tufts University. "There is a lot of circumstantial evidence that they cause cancer in animal studies, that they are hormone disruptors. Remember, these are neurotoxins," Krimsy said, adding that most studies done on the effects of spraying focused on agricultural spraying — not spraying in populated areas.
"We simply don't know what effects it's going to have, the indiscriminate spraying on human populations," he added.
So far this year, officials have reported 112 human cases of West Nile, more than half in the past week, according to the Centers for Disease Control and Prevention (CDC). Most of these infections are in Louisiana. Mississippi and Illinois also have reported human infections of the virus, which began showing up in the United States in New York three years ago.
Residents Protest Dangerous Pesticides
In Hays County, Texas, residents effectively stopped spraying in many of their neighborhoods. They protested, carrying posters decrying the "chemical warfare" on their families. County commissioners agreed to severely limit mosquito spraying near those homes.
In Jefferson County, Ala., health officials are trying to decide what to do. Many cities, including Birmingham, have been spraying for weeks. County officials, though, haven't started their own spraying efforts because they aren't convinced spraying is all that effective against mosquitoes.
But after a case of West Nile infection was recently discovered in Alabama, some residents began demanding that the county spray.
Brian Debrow, the environmental health program manager at the Jefferson County Health Department, says the county may start spraying in order to ease anxiety. "The public likes seeing the trucks going down the road and spraying for mosquitoes," he said. "It gives them a sense of security they feel like something is being done."
CDC: Least Effective Deterrent
Scientists at the CDC, which is leading the surveillance effort on West Nile virus, do not take a position on whether local health departments should spray for mosquitoes. But they do point out that spraying is the least effective method of slowing the spread of the insects.
Since adult mosquitoes only live for about two weeks at the most — whether they're sprayed or not — the most effective way to limit mosquitoes is to keep them from breeding. And that means emptying out pools of water where they lay their eggs.
"These would include things like old tires, cans, flower pots and so forth, just do an inspection and see what's out there that might serve as a breeding ground for the mosquitoes," points out Dr. Julie Gerberding, the director of the CDC.
And that's exactly what Washington, D.C. health officials are doing. They've decided that spraying pesticides into the air is too risky, especially since the incidence of asthma in the city is already high.
Instead, they are targeting small amounts of pesticides directly into pools of standing water and ditches where mosquitoes are breeding. And they're going door-to-door with pamphlets that explain to residents how best to avoid mosquitoes altogether.
Even so, in the states where West Nile virus has been discovered, there is pressure on health officials to appear to be fighting the virus on every front and many feel the most convincing approach is the most visible one — spraying chemicals out where everyone can see.