The plans for aerial spray missions are to target mosquito larvae in large, wet bodies of water.  These treatments are only used when there is a demonstratable increase in larvae counts, which will produce high levels of adult mosquitoes.

The two products used for aerial larviciding are B.t.i. and Methoprene.

B.t.i. (Bacillus thuringiensis subspecies israelensis) is a beneficial microorganism that can be used in organic gardening without destroying the natural balance that exists between pests and predators (Ellis & Bradley, 1992).   B.t.i. is applied to standing water for control of the larval stage of the mosquito life cycle.   The microorganism is ingested and the toxin disrupts the gut by binding to receptor cells present in the mosquito larva.

Methoprene is an insect growth regulator, which prevents immature mosquitoes from maturing into adults (Ellis & Bradley, 1992).  

Neither of these products affects beneficial insects and both are supported by many home organic gardeners.   In addition to being non-toxic to beneficial insects and mammals, there is little opportunity for human exposure, since the material is applied directly to ditches, ponds, marshes, or flooded areas that are not drinking water sources.

Reference:

Ellis, B.W., & Bradley, F.M. (1992).  The Organic Gardener’s Handbook of Natural Insects and Disease Control.