Suffolk County is planning to do ground spraying for adult mosquitoes Thursday on Fire Island, and aerial spraying for mosquito larvae Friday on area salt marshes, health officials said.

Water Island, Atlantique, Summer Club and Fire Island Pines are to be sprayed Thursday from 6 to 10 p.m. with the pesticide Anvil, officials said.

Besides being annoying, some mosquitoes' bites can transmit West Nile virus to humans.

The chances of experiencing health effects from the ground spraying are "quite low," the health department said, but children and pregnant women should avoid exposure if possible by staying clear of the area during spraying and at least 30 minutes after.

Among the "common-sense steps" the department suggests is closing doors, windows and air-conditioning vents during spraying and 30 minutes after.

On Friday, from 5 a.m. to 8 p.m., some Suffolk salt marshes will be treated with the pesticide Vectobac 12AS. Precautions are not necessary, health officials said, as "the helicopter will be flying at a very low level over marsh areas and taking other precautions to control airborne drift into inhabited areas." Also, pesticides used "have no significant human toxicity," they said.

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The marshes are located in areas of the towns of Islip, Brookhaven, Southold, Riverhead and Babylon.

For more information, call Suffolk's spraying information hotline at 631-852-4939 or visit