The New York City Department of Health and Mental Hygiene is spraying city neighborhoods against mosquitoes that may carry and spread the Zika virus,1 2 3 which officials at the U.S. Centers for Disease Control and Prevention (CDC) and National Institutes of Health (NIH) have concluded is the cause of the infant birth defect microcephaly.4 New York City public health officials are now using low-flying helicopters to release pellets of the pesticides Altosid and VectoBac over four of New York City’s five boroughs, including Brooklyn, Queens, Staten Island, and The Bronx.1 3

Specific areas targeted for spraying are “marshland and other urban wetlands.” In Brooklyn, these include Marine Park and Fresh Creek Park. In Queens,  it is Alley Pond Park, the now dormant Flushing Airport, Dubos Point Wildlife Sanctuary and Park, and Brookville Park. In Staten Island, areas include Goethals North, Corporate Park, Saw Mill Marsh, Chelsea, Fresh Kills, La Tourette, Port Mobile, Wolfes Pond Park, Blue Heron Park, South Beach, Old Town, Clove Lake Park, and Kissena Park. In  The Bronx, it’s Pelham Bay Park.1 3

Altosid is a trade name for the insect growth regulator (IGR) Methoprene. According to the U.S. Environmental Protection Agency (EPA), Methoprene “interferes with an insect’s life cycle and prevents it from reaching maturity or reproducing.”5 It essentially attacks mosquitoes when they are in their larval stage of development in water, before they hatch and are able to fly. Other trade names for the larvicide are Apex, Diacon, Dianex, Extinguish, Fleatrol, Kabat, Ovitrol, Pharorid, and Precor.5

With regard to Altosid’s toxicity to humans, fact sheets made available by local governments state:

Risk to the general public from the use of Altosid is minimal. Avoiding exposure is always the safest course of action, particularly for populations that may be at higher risk such as pregnant women, children, the elderly and those with chronic illnesses.6 7

VectoBac is a trade name for the bacterial insecticide Bacillus thuringiensis israelensis (Bti). Other trade names include Aquabac, Teknar, and LarvX, but there are a total of 25 Bti products registered for use in the United States.8 According to the EPA:

Mosquito larvae eat the Bti product which is made up of the dormant spore form of the bacterium and an associated pure toxin. The toxin disrupts the gut in the mosquito by binding to receptor cells present in insects, but not in mammals.8

According to the National Pesticide Information Center (NPIC), “Bti is low in toxicity to people and other mammals.” With regard to birds and fish, Bti has been found to be “practically non-toxic and non-pathogenic.”9

Although both insect growth regulators and bacterial insecticides are thought to be relatively harmless to humans, they are still toxic to some degree. Note above, for example, the risk of Altosid to the public is described as minimal, and the toxicity of Bti is characterized as low.