Diazinon is an organophosphate pesticide used as an insecticide, acaricide (for ticks and mites), and nematicide (for nemotodes 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] There are 11 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 probably carcinogenic to humans (Group 2A) in its 2015 assessment of the carcinogenicity of five organophosphate pesticides. IARC found limited evidence of carcinogenicity in humans for lung cancer and non-Hodgkin lymphoma from studies of agricultural exposures in the USA and Canada.[4-6] 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.
Agreement Respecting the Great Lakes Basin Ecosystem
Canadian Council of Ministers for the Environment (CCME) Water Quality Guideline
Rank = “Medium hazard”
WHO’s Drinking Water Guideline
Excluded from guideline values because it is “unlikely to occur in drinking-water”
ppm - Parts per million
MAC - Maximum allowable concentration
Canadian Legal Status
Pest Control Products Act, SC, 2002, c 28
List of Pest Control Product Formulants and Contaminants of Health or Environmental Concern, SI/2005-114
Pest Control Products Regulations, SOR/2006-124
AB, BC, NB, NL, NT, NU, PEI, QC, SK, YK
Non-Essential Pesticide Use Regulation, Man Reg 285/2014
Diazinon is not allowed for domestic/cosmetic use
List of Allowable Pesticides Regulations, NS Reg 181/2010
Diazinon is not allowed for domestic/cosmetic use.
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 risk to human health and the environment from pesticide products, which may include a restriction on sales, production, or trade.[31,32] 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, the most comprehensive restrictions on lawn and garden pesticides in North America, prohibits the use of over 250 pesticide products and over 95 pesticide ingredients, including diazinon, for cosmetic use.
Diazinon is an organophosphate pesticide used as an insecticide, acaricide (for ticks and mites), and nematicide (for nemotodes 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. It is primarily used in the agricultural sector, 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 and turf, agricultural applications, livestock and insect control, and home gardens; however, concerns regarding its toxicity led to phase-out programs in North America beginning in 2004.[8,35] It has been banned for use in the United States on golf courses and sod farms since 1988, after decimating congregating bird flocks.
Examples of diazinon use in Canada include:
Agricultural: Diazinon is currently used in Canada for selected insect control on berries, fruits, nuts, ground crops, cereals, tobacco, and Christmas trees. Several of these applications have been 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 includes 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 with 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 been tracking and reporting 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. Less than 50,000 kg a.i. of diazinon was sold in Canada in 2009. In 2008, diazinon was ranked as having the 10th highest sales of insecticide of kg a.i, with more than (>) 50,000 kg a.i. sold in Canada in 2008. For the remaining years reported, diazinon was not among the top 10 insecticides sold in Canada.
The application and sales of diazinon varies 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, PEI, NS, 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 27,796 kg a.i. sold per annum between 2003-2010. In contrast, Ontario had 7,979 kg a.i. and Alberta had 2,542 kg a.i. in sales in 2008.[41,42]
Canada imported an average of 75 kg of diazinon from 2007 to 2011 primarily from the United Kingdom, followed by Germany and the United States. Canada did not export any diazinon during this same time period.
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 on the job.[3,8] Para-occupational exposure to this pesticides has also been observed in children and family members of those who apply and use diazinon. It is expected that the potential for occupational exposure will decrease substantially when the PMRA phase-out period is completed in December 2016, as diazinon will no longer be available to apply by air-blast, spray, dusts, or granules, and only ear tag and soil drenching will be acceptable.
Food is considered to be 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), by touching recently sprayed plants, or from drinking contaminated waters. An individual may be exposed through inhalation, skin, or ingestion.
Diazinon may enter the environment from agricultural applications, where it may 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.[8,45] Diazinon is metabolized in animals that may come into contact with it, and it does not bioaccumulate or biomagnify.
In a large national water quality study conducted in 2003-2005, diazinon was found in concentrations of 46-106 nanograms per litre (ng/L) in precipitation, 0.04-12,500 ng/L in surface water, 11-2,700 ng/L in runoff, and 0.007-2.14 ng/L in ground waters in the Lower Fraser Valley and the Okanagan Basin, BC. In this study, samples of precipitation, surface water, and runoff exceeded the suggested limit for diazinon concentrations in water of 0.08 ug/L, or 80 ng/L.  It was not detected in water samples in Alberta, Saskatchewan, Manitoba, or Quebec. In Ontario, 11 of the 162 (7%) and 4 of the 160 (3%) water samples taken in 2003 and 2005, respectively, exceeded the benchmark level.
Our team has performed a detailed scan of exposure control resources and assembled a compilation of key publications and resources. These are organized by type of exposure (environmental or occupational) and by specificity (general or carcinogen-specific). Please visit our Exposure Reduction Resources page to view.
We also recommend exploring the Prevention Policies Directory, a freely-accessible online tool offering information on policies related to cancer and chronic disease prevention. Providing summaries of the policies and direct access to the policy documents, the Directory allows users to search by carcinogen, risk factor, jurisdiction, geographical location, and document type. Click here to learn more about policies specific to diazinon in the Directory. For questions about this resource, please contact a member of the Prevention Team at the Canadian Partnership Against Cancer at firstname.lastname@example.org.
Waddell, B. L. et al. Agricultural use of organophosphate pesticides and the risk of non-Hodgkin’s lymphoma among male farmers (United States). Cancer Causes Control 12, 509–517 (2001)
McDuffie, H. H., Pahwa, P., McLaughlin, J. R., Spinelli, J. J. & Fincham, S. Non-Hodgkin’s lymphoma and specific pesticides exposures in men: cross-Canada study of pesticides and health. Cancer Epidemiol. Biomarkers Prev. 10, 1155–1163 (2001)
Guyton, K. Z. et al. Carcinogenicity of tetrachlorvinphos, parathion, malathion, diazinon, and glyphosate. Lancet Oncol. 16, 490–491 (2015)
Toxipedia(Search term: Diazinon, accessed September 2015)