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Information on Aerial Spraying

When people in a large area are getting sick or when large numbers of mosquitoes are found, airplanes can be used to treat very large areas with insecticides safely, quickly, and efficiently. This process is called aerial spraying. Below is more information on aerial spraying.

Aerial Spraying and Mosquito Control

Is aerial spraying an effective tool for killing mosquitoes?

Aerial treatment of areas with products that rapidly reduce both adult mosquitoes and their larvae that carry the Zika virus can be effective. Repeated aerial applications of insecticide has reduced mosquito populations as a part of an integrated mosquito management program.

Is aerial spraying alone the best way to control mosquitoes?

  • Aerial spraying is only one part of the solution for controlling mosquitoes, but it is the one method that can rapidly reduce the number of mosquitoes spreading Zika in a large area.
    • It is the most effective method when large areas must be treated quickly.
  • Aerial spraying is used as part of an integrated mosquito control program to quickly reduce the number of mosquitoes responsible for infecting people with viruses like Zika, dengue, or chikungunya.
  • An integrated mosquito control program includes
    • Source reduction.  Eliminating mosquito habitats, such as discarded containers and rain gutters.
    • Structural barriers, such as screens and enclosed, air-conditioned spaces, if possible.
    • Larval mosquito control using the appropriate methods for the habitat.
    • Adult mosquito control using insecticides.
    • Community education efforts related to preventing mosquito bites by wearing EPA-registered insect repellents and protective clothing (long-sleeved shirts and long pants).

Aerial Spraying and Insecticides

How is an insecticide chosen for use in aerial spraying?

  • State and local officials make the decision on what insecticide(s) to use for aerial spraying.
  • The decision is based on the results of insecticide resistance testing in the target area.

Is aerial spraying experimental?

  • Aerial spraying is not experimental.
  • EPA-registered insecticides are used for aerial spraying. EPA-registered insecticides have been studied for their effectiveness and safety when used according to label instructions.
  • Aerial spraying, using Naled and other insecticides, has been used in many populated areas of the continental United States, including Miami, Tampa, and New Orleans, to help control mosquitoes.
    • In 2014, almost 6 million acres of land in Florida was aerial sprayed with Naled by mosquito control programs.

Where has Naled been used?

  • Naled has been extensively used since the 1950s and is currently applied by aerial and ground spraying to an average of approximately 16 million acres of the continental United States annually.
  • It is also used for mosquito control following natural disasters, such as hurricanes and floods. (Human Exposure to Mosquito-Control Pesticides ― Mississippi, North Carolina, and Virginia, 2002 and 2003, CDC, 2005)
  • In 2004 and 2005, it was used as part of the emergency responses to Hurricanes Charley, Jeanne, Frances, and Katrina.
  • Naled is currently used in the United States by many local governments and mosquito control districts, including the Florida Keys Mosquito Control District, the Lee County Mosquito Control District, and Miami-Dade County.
  • Historically, Naled has been used in Puerto Rico in attempts to control dengue.

What happens to Naled once it is sprayed?

  • Naled starts to degrade (break down) immediately on surfaces, in water, and in sunlight.
  • The chemical dichlorvos (DDVP) can be created when Naled degrades. It also breaks down quickly.
  • In small quantities DDVP has not been shown to cause health problems in people.
  • DDVP does not build up in breast milk or breast tissue. 

What is Bti and how does it work?

  • Bacillus thuringiensis subspecies israelensis (Bti) is a naturally occurring bacteria found in soils.
  • Bti produces toxins that kill the larvae of mosquitoes and blackflies when swallowed. The toxins cause death by starvation and only begin working when swallowed by certain insects (larvae of mosquitoes, blackflies, and fungus gnats). 
  • There are several strains of Bacillus thuringiensis (Bt) that kill other insect larva like caterpillars and beetles. These are not the same as Bti.

Can Bti only be applied through aerial spraying?

  • No, Bti is often applied using methods that are not aerial spraying.
  • Bti can be applied using truck-mounted or backpack spraying. It can also be found as dunks or briquettes that can be put in areas of standing water that cannot be emptied, such as fountains and ornamental ponds, septic tanks, and unchlorinated pools.
  • Dunks are currently being distributed in Zika prevention kits.

Aerial Spraying and Human Health

Is aerial spraying of insecticides dangerous/harmful to human health?

  • No, during aerial spraying, a small amount of insecticide is sprayed over an area, about 1 ounce (two tablespoons) per acre or about the size of a football field.
  • This small amount does not pose a health risk to people or pets in the area that is sprayed.
  • When aerial spraying is done correctly, it does not cause asthma attacks.
  • There is a possibility that spraying of a larvicide, like Bti, can cause eye irritation if a person is outside and looking up when spraying takes place.
  • EPA-registered products are used for aerial spraying. The label instructions are followed by a licensed professional.
  • If people prefer to stay inside and close windows and doors when spraying takes place they can, but it is not necessary.

Does aerial spraying cause asthma attacks?

  • No, when aerial spraying is done correctly, it does not cause asthma attacks.
  • When applied according to label instructions, EPA-registered insecticides do not pose a risk to human health or the environment.
  • Research shows that ultra-low volume (ULV) application for mosquito control does not increase the risk of asthma for people living in treatment areas (Karpati et al. 2004, Currier et al. 2005, Duprey et al. 2008). 

Will Naled cause cancer?

  • No, EPA has classified Naled as Group E “Evidence of Non-carcinogenicity for Humans,” meaning that there is no evidence that it causes cancer in people.
  • During aerial spraying, a small amount of insecticide is sprayed over an area, about 1 ounce (two tablespoons) per acre or about the size of a football field.
  • Droplets float in the air and kill adult mosquitoes on contact. 
  • Naled starts to degrade (break down) immediately on surfaces, in water, and in sunlight.
  • EPA conducted risk assessments for Naled and calculated risks under different exposure scenarios.
  • Because of the very small amount of active ingredient released per acre of ground during aerial spraying, EPA found that for all scenarios and exposures were hundreds or thousands of times below an amount that might pose a health concern.
  • In an evaluation of thousands of people who conducted agricultural spraying using many types of insecticides, including organophosphates like Naled, no increased risk of any type of cancer was found during the 7-11 years of follow up (Schinasi & Leon, 2008).
  • However, at high doses, for example if the person doing the spraying is exposed to Naled directly in amounts that are well above those for normal labeled uses, Naled and other organophosphates can overstimulate the nervous system, causing nausea, dizziness, or confusion. This is why it is very important that those who actually work with Naled strictly follow label instructions.
    • Severe high-dose poisoning with any organophosphate can cause convulsions, respiratory paralysis, and death.
    • It is extremely unlikely that any person would come into contact with this amount of Naled when it is applied by a licensed professional according to label instructions.

Will Bti affect human health?

  • Bti has not been found to pose a health risk to people or pets.
  • There is a possibility that spraying larvicides, like Bti, can cause eye irritation if a person is outside when spraying takes place.
  • Bti is an EPA-registered insecticide. EPA-registered insecticides have been studied for their effectiveness and safety when used according to label instructions.
  • Existing residential and area-wide uses, like aerial or truck spraying, have been evaluated and found to be safe. Using Bti to kill mosquito larvae may reduce the risk of getting infected with Zika virus.
  • If people prefer to stay inside when spraying takes place they can, but it is not necessary.

Aerial Spraying and Animals

Will aerial spraying hurt pets and other animals?

  • No, when aerial spraying is done correctly, it does not harm animals.
  • During aerial spraying, a small amount of insecticide is sprayed over an area, about 1 ounce (two tablespoons) per acre, or about the size of a football field.
  • This small amount does not pose a health risk to people or pets in the area that is sprayed.
  • EPA-registered products are used for aerial spraying. The label instructions are followed by  a licensed professional.If people prefer to bring pets inside when spraying takes place they can, but it is not necessary.
  • Aerial spraying will not harm  fish or animals that live in the water. People do not need to cover fish ponds when spraying takes place. If a larvicide is sprayed, it is better if ponds are not covered.

Will aerial spraying kill bees?

  • Aerial spraying can be done in ways that minimize risk to bees.
  • Spraying Naled can kill bees outside of their hives at the time of spraying; therefore, spraying is limited to dawn or dusk when bees are inside their hives.
  • Because Naled breaks down quickly, it does not pose a risk to the honey bee populations.
    • Studies show that honey production between hives in treated and untreated sites did not show significantly different quantities of honey over the course of a season.
    • For additional protection, urban bee keepers inside the spray zone can cover their hives when spraying occurs.
  • Although significant exposure to bees would not occur with Naled application at dawn and dusk, beekeepers can reduce potential exposure to bee colonies even more by covering colonies and preventing bees from exiting during designated treatment periods or, if possible, relocating colonies to an untreated site. 
  • The spraying of mosquito larvicides will not impact bees.

Will aerial spraying kill birds or other animals?

  • No, when aerial spraying is done correctly, it does not harm birds or other animals.
  • The insecticides used for aerial spraying do not pose risks to wildlife or the environment.
  • Aerial spraying does not cause long-term harm to the environment or local ecosystem, even if spraying happens more than once.
  • EPA-registered insecticides used for aerial spraying break down rapidly in the environment, and it displays low toxicity to birds and mammals.
  • Aerial spraying will not harm coquis or fish or animals that live in the water. People do not need to cover fish ponds when spraying takes place. If a larvicide is sprayed, it is better if ponds are not covered.

Will Bti affect animals or wildlife?

  • No, Bti does not pose a risk to other mammals, birds, or aquatic life, including coqui frogs in Puerto Rico and USVI. The toxins it produces only begin working once swallowed by certain insects (larvae of mosquitoes, blackflies, and fungus gnats).

Aerial Spraying and the Environment

Will aerial spraying pollute water?

  • No, when aerial spraying is done correctly, it does not pollute water.
  • Research shows that, when applied according to label instructions, EPA-registered insecticides sprayed in low levels (about two tablespoons per acre [4,046 square meters]) does not cause long-term harm to the environment or local ecosystem, even if spraying happens more than once.

Will chemicals from aerial spraying contaminate soil?

  • No, when chemicals used in aerial spraying are used correctly, they will not contaminate soil.
  • Aerial spraying does not cause harm to the environment or local ecosystem, even if spraying happens more than once.
  • When applied according to label instructions, EPA-registered insecticides do not pose a risk to human health or the environment.

More information can be found on the US Environmental Protection Agency’s website.

Is Bti harmful to crops or water supplies?

Bti is not toxic to people. It has not been shown to make people sick. When used as directed, Bti can be applied safely to standing water where mosquitoes lay eggs without causing harm to food crops or water supplies. Bti is EPA-registered for use in residential, commercial, and agricultural settings. Organic farming operations use Bti.

Multiple Bti products are available for use. Some can be used by pest control professionals in certain drinking water storage containers (e.g., cisterns) while others are not EPA-registered for that use. Always follow label instructions. It is important to follow the label for any Bti product to ensure that the product is being used correctly.

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