Mosquito control agencies must now adhere to the federal Clean Water Act which means spraying pesticides over waterways where mosquitoes breed may be tougher.

Catherine Smith is with the Mosquito and Vector Control Association of California. She says some cash-strapped agencies won't be able to afford new permit fees and water quality monitoring tests.

"The chance of people getting bit more and higher exposure to potential vector-borne diseases like West Nile is really likely under these new restrictions."

But Mae Wu with the Natural Resources Defense Council supports the restrictions.

"This is not trying to ban spraying of pesticides at all. They will be able to continue doing their jobs. They just have to be careful and make sure they don't do it in a way that hurts people and the water."

Mosquito control districts are trying to get an exemption from additional federal regulations by lobbying lawmakers in Washington.