As parents in Sacramento County, Calif., put their kids to bed on Monday and Tuesday night, a pair of planes flying overhead doused a 30,000-acre area with a fine mist of pesticides. The target of the repeated aerial assault: mosquitoes.

A growing number of the pests harbor the West Nile virus, officials say, but some residents and environmental health advocates fear the risks of exposure to man-made chemicals -- cancer, delayed brain development, hormone disruption, respiratory problems -- may outweigh the danger of the disease.

West Nile, transmitted through the bite of a mosquito, usually triggers only mild flu-like symptoms. On rare occasions, however, it can prove deadly.

"The cure is worse than the disease," said Kim Glazzard, director of the nonprofit Organic Sacramento. "You're spraying poison over thousands of people for the potential of maybe helping a handful of people. And kids are especially susceptible."

A similar argument is currently being voiced in other parts of the country including Boston, New Orleans and Mobile, Ala..