Vector control crews plan to spray chemicals in West San Jose Tuesday night to curb spread of the West Nile virus.
The spraying plans have prompted concerns for some residents about the chemical used in the operation.
County vector representatives say the Pyrethrin-laced fog sprayed over the area will kill most mosquitoes, which pass the West Nile virus. They say the small amount of Pyrethrin, which is found in household insecticides and pet sprays, is safe. But studies have shown that excessive exposure to the insecticide can lead to asthma, headache, nausea and convulsions.