United States Environmental
Protection Agency
Pesticides and Mosquito Control
Updated:
April 17, 2002
Mosquito-borne diseases affect
millions of people worldwide each year. In the United States, some
species of mosquitoes can transmit diseases such as encephalitis,
dengue fever, and malaria to humans, and a variety of diseases to
wildlife and domestic animals. To combat mosquitoes and the public
health hazards they present, many states and localities have
established mosquito control programs. These programs, which are
based on surveillance, can include non-chemical forms of
prevention and control as well as ground and aerial application of
chemical and biological pesticides.
The mission of the Environmental
Protection Agency (EPA) is to protect human health and the
environment. EPA reviews and approves pesticides and their
labeling to ensure that the pesticides used to protect public
health are applied by methods that minimize the risk of human
exposure and adverse health and environmental effects. In relation
to mosquito control, the Agency also serves as a source of
information about pesticide and non-pesticide controls to address
the concerns of the general public, news media, and the state and
local agencies dealing with outbreaks of infectious diseases or
heavy infestations of mosquitoes. The following questions and
answers provide some basic information on mosquito control, safety
precautions, and information on insecticides used for mosquito
control programs.
How
Does EPA Ensure the Safest Possible Use of Pesticides?
EPA must evaluate and register
pesticides before they may be sold, distributed, or used in the
United States. The Agency is also in the process of reassessing,
and reregistering when appropriate, all older pesticides (those
registered prior to 1984) to ensure that they meet current
scientific standards. To evaluate a pesticide for either
registration or re-registration, EPA assesses a wide variety of
potential human health and environmental effects associated with
use of the product. The producer of the pesticide must provide
data from tests done according to EPA guidelines. These tests
determine whether a pesticide has the potential to cause adverse
effects on humans, wildlife, fish, and plants, including
endangered species and non-target organisms. Other tests help to
assess the risks of contaminating surface water or ground water
from leaching, runoff, or spray drift. If a pesticide meets EPA
requirements, the pesticide is approved for use in accordance with
label directions. However, no pesticide is 100 percent
safe and care must be exercised in the use of any pesticide.
How
Are Mosquitoes Controlled with Pesticides and Other Methods?
The first step in mosquito control
is surveillance. Mosquito specialists conduct surveillance for
diseases harbored by domestic and nonnative birds, including
sentinel chickens (used as virus transmission indicators), and
mosquitoes. Surveillance for larval habitats is conducted by using
maps and aerial photographs, and by evaluating larval populations.
Other techniques include various light traps, biting counts, and
analysis of reports from the public. Mosquito control programs
also put high priority on trying to prevent a large population of
adult mosquitoes from developing so that additional controls may
not be necessary. Since mosquitoes must have water to breed,
methods of prevention may include controlling water levels in
lakes, marshes, ditches, or other mosquito breeding sites,
eliminating small breeding sites if possible, and stocking bodies
of water with fish species that feed on larvae. Both chemical and
biological measures may be employed to kill immature mosquitoes
during larval stages. Larvicides target larvae in the
breeding habitat before they can mature into adult mosquitoes and
disperse. Larvicides include the bacterial insecticides Bacillus
thuringiensis israelensis and Bacillus sphaericus,
the insect growth inhibitor methoprene, and the organophosphate
insecticide temephos. Mineral oils and other materials form a thin
film on the surface of the water which cause larvae and pupae to
drown. Liquid larvicide products are applied directly to water
using backpack sprayers and truck or aircraft-mounted sprayers.
Tablet, pellet, granular, and briquet formulations of larvicides
are also applied by mosquito controllers to breeding areas.
Adult mosquito control may be
undertaken to combat an outbreak of mosquito-borne disease or a
very heavy nuisance infestation of mosquitoes in a community.
Pesticides registered for this use are adulticides and
are applied either by aircraft or on the ground employing
truck-mounted sprayers. State and local agencies commonly use the
organophosphate insecticides malathion and naled and the synthetic
pyrethroid insecticides permethrin, resmethrin, and sumithrin for
adult mosquito control.
Mosquito adulticides are applied as
ultra-low volume (ULV) sprays. ULV sprayers dispense very fine
aerosol droplets that stay aloft and kill flying mosquitoes on
contact. ULV applications involve small quantities of pesticide
active ingredient in relation to the size of the area treated,
typically less than 3 ounces per acre, which minimizes exposure
and risks to people and the environment.
What
Can I Do to Reduce the Number of Mosquitoes in and Around My Home?
The most important step is to
eliminate potential breeding habitats for mosquitoes. Get rid of
any standing water around the home, including water in potted
plant dishes, garbage cans, old tires, gutters, ditches,
wheelbarrows, bird baths, hollow trees, and wading pools. Any
standing water should be drained, including abandoned or unused
swimming pools. Mosquitoes can breed in any puddle that lasts more
than 4 days. Make sure windows and screen doors are "bug
tight." Replace outdoor lights with yellow "bug"
lights. Wear headnets, long-sleeved shirts, and long pants if
venturing into areas with high mosquito populations, such as salt
marshes or wooded areas. Use mosquito repellents when necessary,
always following label instructions.
Should
I Take Steps to Reduce Exposure to Pesticides During Mosquito
Control Spraying?
Generally, there is no need to
relocate during mosquito control spraying. The pesticides have
been evaluated for this use and found to pose minimal risks to
human health and the environment when used according to label
directions. For example, EPA has estimated the exposure and risks
to both adults and children posed by ULV aerial and ground
applications of the insecticides malathion and naled. For all the
exposure scenarios considered, exposures ranged from 100 to 10,000
times below an amount of pesticide that might pose a health
concern. These estimates assumed several spraying events over a
period of weeks, and also assumed that a toddler would ingest some
soil and grass in addition to dermal exposure. Other mosquito
control pesticides pose similarly low risks. (For more details on
health and environmental risk considerations, see the separate EPA
fact sheets on the specific mosquito control pesticides.)
Although mosquito control
pesticides pose low risks, some people may prefer to avoid or
further minimize exposure. Some common sense steps to help reduce
possible exposure to pesticides include:
-
Pay attention to the local
media for announcements about spraying and remain indoors
during applications in the immediate area.
-
People who suffer from
chemical sensitivities or feel spraying may aggravate a
preexisting health condition, may consult their physician or
local health department and take special measures to avoid
exposure.
-
Close windows and turn off
window-unit air conditioners when spraying is taking place in
the immediate area.
-
Do not let children play near
or behind truck-mounted applicators when they are in use.
|
