PESTICIDES – PROBABLE CARCINOGEN (IARC 2A)
- A pesticide used to kill ticks, mites, and roundworms on various crops; its use is declining
- Associated cancers: Lung cancer, non-Hodgkin lymphoma (limited evidence)
- Most important route of exposure: Ingestion, skin contact
- Uses: Control of insects on berries, fruits, nuts, ground crops, cereals, tobacco, and Christmas trees
- Occupational exposures: Via applying or manufacturing diazinon
- Environmental exposures: Primarily via food, but food residue levels tend to be low
- Fast fact: Domestic use of diazinon is prohibited in Canada.
Diazinon is an organophosphate pesticide used as an insecticide, acaricide (for ticks and mites), and nematicide (for nematodes or roundworms). Depending on purity, it may be a colourless oil to an amber or brown liquid. Diazinon’s chemical name is O,O-diethyl O-2-isopropyl-6-methylpyrimidin-4-yl phosphorothioate, and it is sold under trade names such as Diazol®, Protector Ear Tags®, and Diazol Oil®.[1,2] As of 2016, there are nine products containing diazinon as an active ingredient registered with the Canadian Pest Management Regulatory Agency (PMRA), none of which are registered for domestic use.
The International Agency for Research on Cancer (IARC) reclassified diazinon as Group 2A, probably carcinogenic to humans, in its 2015 assessment of the carcinogenicity of five organophosphate pesticides. IARC’s review looked at studies of agricultural exposures in the USA and Canada, which found limited evidence of carcinogenicity in humans for lung cancer and non-Hodgkin lymphoma.[4,5,6] There was also limited evidence that diazinon causes cancer in animals, but convincing mechanistic evidence that it can induce DNA or chromosomal damage in animal and cell culture studies.
Diazinon exposure in humans can lead to a variety of symptoms and effects, depending on the degree of exposure. It typically affects the nervous system, causing symptoms such as headache, dizziness, anxiety, eye pupil constriction, and in extreme cases, difficulty breathing, coma, or death.
Regulations and Guidelines
Occupational exposure limits (OEL)[9,10,11,12,13,14,15,16,17,18,19,20,21,22,23]
|Canadian Jurisdiction||OEL (mg/m3)|
|Canadian Labour Code||0.01 [TWA; IFV; Skin]|
|AB||0.01 [TWA; skin]|
|BC||0.01 [TWA; v; skin]|
|NB||0.01 [TWA; skin]|
|MB, NS, NL, ON, PE||0.01 [TWA; IFV; skin]|
|QC||0.1 [TWA; skin]|
|YT||0.01 [TWA; skin]
0.03 [stel; skin]
|NT, SK, NU||0.01 [TWA; IFV; skin]
0.03 [stel; IFV, skin]
|Other Jurisdictions||OEL (mg/m3)|
|ACGIH 2020 TLV||0.01 [TWA; IFV; skin]|
mg/m3 = milligrams per cubic meter
TWA = time-weighted average, assuming a typical 8-hour workday and a 40-hour workweek of a chemical substance present in the air in a worker’s respiratory zone
IFV = inhalable fraction and vapour
skin = easily absorbed through the skin; identifies substances that contribute significantly to overall exposure by the skin route
v = inhalable fraction, vapour and aerosol
stel = short term exposure limit (15 min. maximum)
ACGIH = American Conference of Governmental Industrial Hygienists
TLV = threshold limit value
Canadian environmental guidelines and standards*
|Ontario Ambient Air Quality Criteria||24 hours: 3 µg/m3||2016|
|British Columbia’s Contaminated Sites Regulation||Sets soil standards for the protection of human health:
Agricultural and low density residential sites: 10 μg/g
Urban park and high density residential sites: 20 μg/g
Commercial and industrial sites: 150 μg/g
Drinking water: 20 μg/L
|Quebec’s Regulation Respecting the Quality of Drinking Water||MAC = 0.014 mg/L||2012|
|Canada’s and Manitoba’s Drinking Water Guidelines||MAC = 0.02 mg/L||2005
|Ontario Drinking Water Quality Standards||MAC = 0.02 mg/L||2003|
|Health Canada’s Maximum Residue Limits for Foods||Food type:
Cantaloupes, watermelons: 0.25 ppm
Swiss chard: 0.25 ppm
Cucumbers: 0.5 ppm
Brussels sprouts: 0.5 ppm
Strawberries: 0.75 ppm
Kale, spinach: 0.75 ppm
Apricots, plums, pears: 0.75 ppm
Range: 0.25-0.75 ppm
|CCME Water Quality Guideline||Rank = “Medium hazard”||2008|
|WHO Drinking Water Guideline||Excluded from guideline values because it is “unlikely to occur in drinking-water”||2011|
**Standards are legislated and legally enforceable, while guidelines (including Ontario ambient air quality criteria) describe concentrations of contaminants in the environment (e.g. air, water) that are protective against adverse health, environmental, or aesthetic (e.g. odour) effects
µg/m3 = micrograms per cubic meter
MAC = maximum allowable concentration
ppm = parts per million
µg/L = micrograms per liter
CCME = Canadian Council of Ministers of the Environment
WHO = World Health Organization
Canadian legal status
|Federal||Pest Control Products Act, SC, 2002, c 28||Not included|
|Pest Control Products Regulations, SOR/2006-124||Not included|
|AB, BC, NB, NL, NT, NU, PEI, QC, SK, YK||Multiple titles||Not included|
|MB||Non-Essential Pesticide Use Regulation, Man Reg 285/2014||Diazinon is not allowed for domestic/cosmetic use.|
|NS||List of Allowable Pesticides Regulations, NS Reg 181/2010||Diazinon is not allowed for domestic/cosmetic use.|
|ON||Pesticides Act, RSO 1990, c P. 11, as amended by the Cosmetic Pesticides Ban Act, 2008, S.O. 2008, c. 11 – Bill 64 – Assented to: June 18, 2008||Diazinon is not allowed for domestic/cosmetic use.|
Several provincial, territorial, and municipal governments have passed laws to reduce the risk of pesticide products to human health and the environment. These may include restrictions on sales, production, or trade.[34,35] Although several provinces and one territory have implemented some form of cosmetic pesticide policy (QC, 2003; NB, 2009; ON, 2009; AB, 2010; PEI, 2010; NS, 2010; NL, 2012; YK 1994), only the Ontario and Nova Scotia legislation is considered strong enough to significantly reduce cosmetic pesticide exposure. For example, Ontario’s Cosmetic Pesticide Ban Act, which has the most comprehensive restrictions on lawn and garden pesticides in North America, prohibits the cosmetic use of over 250 pesticide products and over 95 pesticide ingredients, including diazinon.
Diazinon is an organophosphate pesticide used as an insecticide, acaricide (for ticks and mites), and nematicide (for nematodes or roundworms). Diazinon is non-systemic, which means it must come into direct contact with the target species and does not circulate within the plant. It may be applied as dust, granules, spray, seed dressing, and within impregnated materials. Diazinon is primarily used in the agricultural sector and on livestock, although its use is being reduced in Canada. Diazinon is not available for domestic use in Canada.
Historically, diazinon was widely used in Canada across a range of settings, such as for lawn, turf, and home gardens; however, concerns regarding its toxicity led to phase-out programs in North America beginning in 2004.[8,38] Diazinon has been banned for use in the United States on golf courses and sod farms since 1988, after decimating congregating bird flocks.
Diazinon is used in the agricultural sector. Diazinon is currently applied in Canada for selected insect control on berries, fruits, nuts, ground crops, cereals, tobacco, livestock, and Christmas trees. Several applications were recently subjected to a phase-out period according to a PMRA re-evaluation in 2013. For critical uses of diazinon, where no alternative products were identified, longer-term phase-outs were implemented to allow transition strategies and alternative risk management tools to be developed. The phase-out included ceasing the use of diazinon for fruit trees (including apricot, peach, plum) by December 2013, and for Christmas trees, several berries (strawberries, raspberries, loganberry, gooseberry), root vegetables (carrots, radish, turnip, rutabaga), fruit trees (apple, pear), and tobacco by December 2016. The PMRA stated that using diazinon for soil drenching and for ear tag applications remains acceptable. Soil drenching is an application method where a mixture of pesticide and water is applied directly to the base of an infected tree. Ear tags are often used to control fleas and ticks in livestock.
Canadian Production and Trade
Since November 2006, the PMRA has tracked and reported sales information on Canadian pesticides. There was between 50,000-100,000 kilograms of active ingredient (kg a.i.) of diazinon sold in Canada in 2010, 2011, 2012, 2013, and 2015. Less than 50,000 kg a.i. of diazinon was sold in Canada in 2009, 2014, and 2017. In 2016, diazinon was the third most commonly sold insecticide, with over 500,000 kg a.i. sold in Canada. Most recently, in 2018 and 2019, between 1,000-5,000 kg a.i. were sold each year.
The application and sales of diazinon vary considerably by each province in part due to the pest profile of each region. Diazinon was listed as one of the top 10 pesticide active ingredients by sales volume in BC, PE, NS, and NB in 2003. Out of the three provinces where kg a.i. data is available, BC had the highest sales volume, with an average of 42,651 kg a.i. sold in 2015. In contrast, 7,979 kg a.i. were sold in Ontario in 2008, and 135 kg a.i. were sold in Alberta in 2018.[42,43]
TradeMap lists diazinion export and import data; however, reporting for pesticides is not standardized and the data is incomplete.
Environmental Exposures Overview
Food is considered the primary source of human exposure to diazinon, although food residue levels tend to be low. Pesticide residues, including diazinon, are monitored by the Canadian Food Inspection Agency (CFIA) under the National Chemical Residue Monitoring Program (NCRMP). To a lesser extent, people may be exposed when diazinon is applied agriculturally nearby or in urban areas (lawns and gardens). This would occur through touching recently sprayed plants or from drinking contaminated waters. An individual may be exposed through inhalation, skin contact, or ingestion.
Diazinon may enter the environment from agricultural applications, where it can be present in the soil, air, surface waters, and plant surfaces. It may be present in the air as either a vapour or a particulate. Diazinon breaks down relatively quickly in the environment with a half-life ranging from an hour to two weeks, depending on local conditions.[8,46] Diazinon is metabolized in animals that may come into contact with it, and it does not bioaccumulate or biomagnify.
Occupational Exposures Overview
Workers may be exposed to diazinon through inhalation, ingestion, or dermal absorption.
Agricultural workers (such as farmers, farm managers, and labourers) who apply this pesticide, along with those who manufacture it, are the most likely to be exposed at work.[3,8] Para-occupational exposure to this pesticide is also possible in children and family members of those who apply and use diazinon. The potential for occupational exposure is expected to decrease substantially when the PMRA phase-out period ends in December 2016 since diazinon will no longer be available to apply by air-blast, spray, dusts, or granules. Only ear tag and soil drenching will be acceptable.
CAREX Canada has not prioritized diazinon 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.
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