PESTICIDES – POSSIBLE CARCINOGEN (IARC 2B)
- A pesticide used primarily in agricultural and horticultural sectors
- Associated cancers: Kidney cancer, stomach cancer (animal studies only)
- Most important route of exposure: Inhalation, skin contact
- Uses: Controls fungal diseases in vegetable, fruit, field, and ornamental crops
- Occupational exposures: In agricultural, manufacturing, and forestry industries
- Environmental exposures: Via residues in food products, living close to agricultural areas, or contaminated water
- Fast fact: Chlorothalonil is also used as a preservative, anti-mold and anti-mildew agent, micro-biocide, algaecide, insecticide, and arachnicide (for spiders).
Chlorothalonil is a colourless and odourless white crystalline solid that is soluble in water. It is used as a fungicide for vegetable, fruit, field, and ornamental crops, as well as lawns and turfs. It may also be referred to as Daconil, Bravo, or 1,3-dicyanotetrachlorobenzene. There are numerous other synonyms and product names; see the Hazardous Substances Data Bank (HSDB) for more information.
Chlorothalonil has been classified by the International Agency for Research on Cancer (IARC) as Group 2B, possibly carcinogenic to humans due to evidence of kidney and stomach carcinogenicity in rats and mice. At the time, no studies examining the carcinogenic effects of chlorothalonil in humans were available. Since then, there have been limited number of studies investigating the relationship between exposure and cancer in humans. Additionally, chlorothalonil can irritate the skin and cause contact dermatitis. It may also irritate the mucous membranes of the eye and respiratory tract.
Regulations and Guidelines
Canadian Environmental Guidelines
Canadian Maximum Residue Limits 2018
|Beans, Broccoli, Brussels Sprouts, Cabbage, Cauliflower, Cucumbers, Melons, Onions, Pumpkins, Squash, Tomatoes, Wasabi||5|
|Carrots, Mushrooms, Parsnips||1|
|Cherries, Peaches, Nectarines||0.5|
|All other foods||0.1|
ppm = parts per million
|Health Canada||DSL – high priority substance
with lowest potential for exposure
|National Classification System
for Contaminated Sites
DSL = domestic substance list
Chlorothalonil has been produced for commercial use since 1969. It is used as an agricultural and horticultural fungicide, bactericide, and nematocide. As a broad spectrum, non-systemic pesticide, it controls fungal diseases in the foliage of vegetable, field, and ornamental crops. It is typically used on: citrus fruits, currants, berries, bananas, tomatoes, green vegetables, coffee, peanuts, potatoes, onions, and cereals.
Canadian Production and Trade
There are 39 products listed with chlorothalonil as an active ingredient registered with the Canadian Pest Management Regulatory Agency (PMRA). Of these, none are registered for domestic use. Some of the trade names chlorothalonil is sold under include Bravo 500®, Daconil®, and Tuffcide®.
The BC and Ontario pesticide surveys report the amount of chlorothalonil used or sold in their respective provinces:
t = tonne
Environmental Exposures Overview
Sources of environmental exposure include ingesting crop residues on foods, living in close proximity to agricultural uses, and drinking contaminated water.[22,23] CAREX Canada estimates that chlorothalonil in air (outdoor and indoor) and dust does not result in an increased risk of cancer (moderate to very low data quality). PMRA’s Proposed Re-Evaluation Decision report for chlorothalonil outlines monitoring studies that have tested for chlorothalonil in municipal drinking water sources and groundwater. The numerous studies were conducted between 1995 and 2008 in various provinces and regions in Canada and found that the detection frequency ranged from 0 to 9%, with arithmetic mean values ranging from 0.01 to 0.092µg/L.
Chlorothalonil is strongly adsorbed to suspended matter in water, and may biodegrade. It is rapidly degraded in soil and does not bioaccumulate in mammals. The amount of chlorothalonil residue on foods depends on application rate, time interval between application and harvest, and type of crop. CAREX Canada estimates that chlorothalonil in foods and beverages does not result in an increased risk of cancer (very low data quality).
The Canadian Food Inspection Agency (CFIA) monitors the Canadian food supply for chemical residues and contaminants in order to ensure they are compliant with maximum residue limits (MRLs) and other tolerances established by Health Canada. Between 2012-2013, the CFIA sampled 1,409 samples of domestic fresh fruit and vegetables as part of the National Chemical Residue Monitoring Program. Of the 1,409 samples, there were 6 violations of the MRLs, which corresponds to a compliance rate of 99.7%. Risk of exposure via ingestion can be decreased through preparation activities such as washing, peeling, and cooking foods.
The PMRA is currently assessing chlorothalonil as part of its re-evaluations, and proposes cancelling a number of registered uses. These include chlorothalonil use on blueberries, celery, cherries, lentils, and turf, as well as its use as a preservative in paint.
Release of chlorothalonil is not reportable to the National Pollutant Release Inventory (NPRI). A search of the US Household Products Database yielded the following results:
US Household Products Database
|US Household Products 2016|
|Search Term||Quantity||Product Type|
|‘Chlorothalonil’||17||Weatherproof glosses (9), pesticides (8)|
For more information, see the environmental exposure estimate for chlorothalonil.
Occupational Exposures Overview
Inhalation and dermal absorption are the most important routes of exposure in occupational settings.
Workers can be exposed to chlorothalonil during production and application, as well as through contact with treated crops. Workers involved in manufacturing or distribution facilities can be exposed via contaminated air or dermal contact. Farmers and pesticide applicators may be exposed via inhalation or dermal absorption during pesticide application or contact with treated
Chlorothalonil is also used in forestry, creating the potential for worker exposure in that industry. Workers in contact with treated wood, such as wood processors and cabinet manufacturers, may also be exposed.
CAREX Canada has not prioritized chlorothalonil for exposure estimate development. This is because a lack of exposure data precluded it in the past. However, the team is investigating new sources of data and methods in order to potentially address this exposure in the future.
- US Environmental Protection Agency (EPA). Integrated Risk Information System, Chlorothalonil (2008)
- ENKON Environmental Limited. Survey of Pesticide Use in British Columbia: 2003 (2005)
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