What is an adulticide?
An adulticide is a chemical used to kill adult insects. If needed, the City of Hamilton will use an adulticide to kill adult mosquitoes, in order to reduce the risk of West Nile virus (WNV) to people.
What product would be used and how will it be applied?
If adulticiding is needed to lower the risk of WNV, the product that would be used is malathion. Malathion is spread into the air from an ultra low volume (ULV) sprayer carried on the back of a pick-up truck. Only a very small amount of malathion is used for any given area.
What is malathion?
Malathion is an insecticide that is used to control insects in agriculture, but it is also used around the world to control mosquitoes. The City of Winnipeg has used malathion for decades to control its mosquito problem.
Is malathion safe to use?
Malathion is an insecticide that has been approved for use in Canada since 1953. Malathion has the most up-to-date and complete safety information available of all products registered to kill adult mosquitoes. Health Canada's Pest Management Regulatory Agency (PMRA) says that malathion does not pose a health concern when used properly to control mosquitoes in an urban setting.
Visit the Links and Resources page for a list of additional websites about West Nile virus.
How do I find out when and where malathion will be applied?
If the decision is made to kill adult mosquitoes, the spraying will only occur on an as needed basis to reduce the risk of WNV, and only in areas with high WNV activity (such as positive mosquitoes, or human cases in high population areas). Adult mosquito control is the final stage of a detailed plan that includes public education, reducing sites where mosquitoes breed, and larviciding. The City will use a variety of methods to make sure that you know where and when the spraying will take place. These will include but are not limited to:
- Ads in local newspapers and announcements on local radio
- Information on the web site www.hamilton.ca/westnile
- Media release to local media in southern Ontario
What can I do to reduce exposure to malathion?
Although malathion is not harmful to you when using the ultra low volume application method, if you wish to further reduce exposure to it, you can do the following:
Before spraying occurs:
- Close all windows, doors and vents.
- Check your air conditioner. Central air conditioning units may remain on. Window air conditioning units may also remain on, but set the vents to “closed” or choose the “re-circulate” option. If you have an older window air conditioning unit that does not have these options, the air conditioner should be turned off.
- Bring pets, pet food and water dishes, as well as toys and laundry inside.
- Cover outdoor furniture and play equipment.
- Cover small home-made fishponds on your property and turn over children's wading pools.
During spraying:
- Stay indoors for approximately half an hour after the application is completed in your neighbourhood.
After spraying:
- Rinse outdoor furniture, barbecues, and play equipment with water.
- Rinse home grown fruits and vegetables (as you would with all produce) with water before cooking or eating.
What are the symptoms of overexposure to malathion?
Health Canada's Pest Management Regulatory Association (PMRA) and the U.S. Environmental Protection Agency license malathion for use in adult mosquito control in urban areas. In the amount that is used for ultra-low volume spraying, it is unlikely that you would experience any side-effects, even if you did not take any additional steps to limit your exposure to malathion.
If by some unforeseen event you have been overexposed to malathion, here are the symptoms to look for:
- headaches, nausea, dizziness, confusion, weakness, diarrhea, eye, skin, nose or throat irritation, and breathing problems.
Anyone who has long lasting or severe side effects to pesticides should seek medical care. These effects can be treated and are not likely to result in any long-term health problems. If you are particularly sensitive to chemical exposure, discuss the issue of spraying with your health care provider. Malathion does have a noticeable odour even when used in very small amounts as in ultra-low volume spraying. If you smell an odour, this does not necessarily mean you have been overexposed to the product.
Does malathion pose risks to the environment?
Malathion breaks down quickly in the environment, especially in moist soil, and it is not toxic to birds and mammals. Malathion is, however, highly toxic to insects, including beneficial insects such as honeybees. Adult mosquito control normally is carried out at nighttime or early morning when honeybees are not as active. Malathion is also highly toxic to fish and aquatic insects found in and around water. Care will be taken to avoid spraying near these areas; however, you should cover garden ponds containing fish.
If there is some risk to the environment, why is the City spraying?
The public health professionals in the City are focused on the safety of City residents. Public safety includes making sure that the treatment is not worse than the disease and that the treatment benefits our health. Scientific research and debate is followed very carefully. When organizations such as Health Canada and the U.S. Environmental Protection Agency (EPA) review insecticides such as malathion, public health staff look at these results very closely.
Both Health Canada and the U.S. EPA are finishing their thorough review of malathion. These reviews are large undertakings in which all of the available research is collected and studied for its strengths and weaknesses. Both Health Canada and the U.S. EPA have concluded that using malathion to kill adult mosquitoes, when using the ultra low volume application method, does not pose unreasonable risks to the general public, to wildlife, or to the environment. Our public health professionals believe that the determinations made by Health Canada and the U.S. EPA are thorough and valid.