PESTICIDES – PROBABLE CARCINOGEN (IARC 2A)
- A synthetic herbicide widely used in agriculture, forestry, industrial sites, and aquatic environments
- Associated cancers: Non-Hodgkin lymphoma (limited evidence)
- Most important routes of exposure: Inhalation, skin contact, and ingestion
- Uses: Kills grasses, annual and perennial plants, vines, shrubs, and trees; many crops such as soybeans, corn, cotton, and canola have been genetically engineered to resist glyphosate
- Occupational exposures: An estimated 37,000 to 55,000 workers are exposed to glyphosate in the agricultural sector
- Environmental exposures: Via diet, domestic application, and living near sprayed areas
- Fast fact: Glyphosate is the most widely sold and applied pesticide in Canada.
Glyphosate is a non-selective organophosphate herbicide widely used in agriculture, forestry, industrial sites (such as rail corridors or transmission lines), and aquatic environments. The use of this herbicide dramatically increased when crops such as soybeans, corn, cotton, and canola were genetically engineered to resist glyphosate. It is the most widely sold and applied pesticide in Canada.
Glyphosate is a colourless, odourless, crystalline solid, also known as gliphosate, glyphosate hydrochloride, or N-(phosphonomethyl)glycine. Glyphosate formulations are typically prepared with the isopropylamine salt of glyphosate, a surfactant (to help it penetrate plants), and other chemicals. As of 2016, there are 194 products listed with glyphosate as an active ingredient registered with the Canadian Pest Management Regulatory Agency (PMRA). Of these, 39 are registered for domestic use. The trade names that glyphosate is sold under include: Round-Up®, Rodeo®, Xtreme®, ByeBye Weed®, TotalEx®, Wipe Out®.
The International Agency for Research on Cancer (IARC) classified glyphosate as probably carcinogenic to humans (Group 2A) in its 2015 assessment of the carcinogenicity of five organophosphate pesticides. There was limited evidence of carcinogenicity in humans for non-Hodgkin lymphoma, which came from a number of studies published since 2001. There was sufficient evidence that glyphosate can cause cancer in laboratory animals. IARC also evaluated mechanistic studies and cited evidence of genotoxicity and oxidative stress associated with glyphosate exposure. In response to this new classification, Health Canada has proposed additional labeling protocols for products containing glyphosate. Monsanto, the leading producer of glyphosate herbicide products, has publicly disagreed with this new classification. Overall, the carcinogenicity of glyphosate is an area of ongoing assessment and debate; a number of hazard or risk assessments are currently underway or were recently completed by regulatory bodies, including the European Food Safety Authority (EFSA) and US EPA.[9,10]
The short-term consequences of ingesting glyphosate formulations are generally mild, transient gastrointestinal effects. Ingesting large amounts of glyphosate formulations (>85 mL) can corrode the gastrointestinal system and cause impairments to the heart, kidneys, and liver. Respiratory distress, unconsciousness, and shock may also result. Dermal or eye exposure to glyphosate formulations can cause irritations. Inhaling spray mist may cause oral or nasal discomfort, tingling, and throat irritation.
Regulations and Guidelines
Occupational Exposure Limits (OEL)
Canadian Environmental Guidelines
|Canadian Drinking Water Guidelines||MAC = 0.28 mg/L||1987, 2017[27,28]|
|British Columbia’s Contaminated Sites Regulation||Soil standards:
Agricultural and low density residential sites: 1.5 mg/g
Urban park and high density residential sites: 3.0 mg/L
Commercial and industrial sites: 25 mg/g
Drinking water standards: 0.28 mg/L
|Quebec’s Regulation Respecting the Quality of Drinking Water||MAC = 0.21 mg/L||2015|
|Health Canada’s Maximum Residue
Limits for Foods
Lentils: 4 ppm
Milk and eggs: 0.08 ppm
Meat (beef, poultry, goat, pork): 0.08 ppm
Oats: 15 ppm
Canola: 20 ppm
Corn: 3 ppm
Wheat: 5 ppm
|WHO’s Drinking Water Guideline||Glyphosate: “Occurs in drinking water at
concentrations well below those of health concern”
ppm = parts per million
MAC = maximum allowable concentration
Canadian Legal Status
|Federal||Pest Control Products Act, SC, 2002, c 28||Not included|
|Pest Control Products Regulations, SOR/2006-124||Not included|
|NL, NT, NU, PE, QC, SK, YT||Multiple titles||Not included|
|AB||Environmental Code of Practice for Pesticides under the Environmental Protection and Enhancement Act, RSA 2000, cE-12||Glyphosate application is restricted to specific application methods, target weeds, distance from bodies of water, and amount of area treated|
|BC||Integrated Pest Management Regulation, BC Reg 604/2004||Glyphosate application is restricted to specific application methods, target weeds, distance from bodies of water, and amount of area treated|
|MB||Non-Essential Pesticide Use Regulation, Man Reg 285/2014||Glyphosate is not allowed for domestic/cosmetic use|
|NB||Pesticides Control Act, RSNB 2011, c 203 (replaced: Pesticides Control Act, RSNB 1973, c P-8)||Glyphosate is not allowed for domestic/cosmetic use|
|NS||List of Allowable Pesticides Regulations, NS Reg 181/2010||Glyphosate 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||Glyphosate is not allowed for domestic/cosmetic use|
Several provincial, territorial, and municipal governments have passed laws to reduce the risks that pesticide products pose to human health and the environment. In the case of glyphosate, this includes 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 use of over 250 pesticide products and over 95 pesticide ingredients, including glyphosate, for cosmetic use.
The herbicidal activity of glyphosate was discovered in 1970, first commercialized by Monsanto in 1974, and registered for use in Canada in 1976. It is currently one of the most widely used herbicides in Canada for agricultural, domestic, forestry, and commercial applications. A number of plants have been genetically engineered to be unaffected by glyphosate, including soybeans, corn, cotton, and canola. Glyphosate is widely used in the agricultural sector in Canada, but also within forestry, industrial weed control, lawn and gardens, and aquatic environments.
Since the PMRA began tracking the sales of pesticides in Canada in 2006, the use of glyphosate has consistently increased. This is primarily due to the increased use of glyphosate-tolerant crops, zero tillage practices (in which the crop is sown directly into soil that has not been tilled since the harvest of the previous crop, to minimize erosion and maximize soil biodiversity), expanded acreage of glyphosate-tolerant corn and canola, and blueberry production.[3,38] Given that glyphosate application is widespread and it is solely used for weed control, weed-resistance is increasingly becoming an issue in many countries. Giant ragweed is one example of a glyphosate-resistant weed, which was first documented in Canada in 2009.
Examples of glyphosate use in Canada include:
- Agricultural: to control weed growth on fence rows, in storage areas, next to glyphosate-tolerant crops, along irrigation canals, and on fallow or non-producing acreage; for minimum and no-tillage farming practices; to renovate pastures; and to remove ground vegetation from fruit orchards.
- Forestry: to remove ground vegetation of deciduous trees, shrubs, and vegetation from conifer forests and tree planting operations.
- Industrial/commercial: to landscape highways, roadsides, railroad right-of-ways, warehouses, storage areas, public waterways, golf courses, cemeteries, and campus grounds.
- Residential: to eradicate poison ivy, poison oak, vines, and perennial weeds from patios, pavements, driveways, rock gardens, and other locations.
Canadian Production and Trade
According to the Reporting Regulations for Pest Control Products Sales Information that came into force in November 2006, all pesticides sold and used in Canada must be registered with Health Canada’s Pest Management Regulatory Agency (PMRA).
The PMRA is currently conducting a re-evaluation of glyphosate, which is expected to continue registration of these products, but calls for updates to product labels to provide additional guidance on safe use for human health and the environment.
Since 2007, glyphosate has consistently had the highest sales volume of all pesticides sold in Canada, with over 25,000,000 kg of active ingredients (kg a.i.) sold per year.[3,42,43,44,45,46] These sales were primarily within the agricultural sector, where glyphosate was ranked as having the highest sales volume of kg a.i. of herbicide. It was not among the top 10 active ingredients sold within the non-agricultural or domestic sector except for in 2007-2008, when it was ranked number 10 for the domestic sector. No information is known about the sales of glyphosate in Canada from 2013 onwards. The global consumption of glyphosate in 2011 was estimated at 650,000,000 kg a.i. per year and increasing.
*Includes total sales within all sectors for BC, AB, and QC, and use data in only the agricultural sector for ON.
**QC uses chemical groups to report on pesticide sales instead of individual active ingredients. Reported values are for phosphonic/phosphinic acids (primarily glyphosate).
Sales data for provinces and territories is limited. However, glyphosate sales have increased significantly between 2003 and 2008-2010 in British Columbia by 106%, in Quebec by 111%, and in Alberta by 112%.[38,50,48] Agricultural glyphosate use in Ontario increased by 76% from 2003 to 2008.
The general population is primarily exposed to glyphosate through their proximity to sprayed areas, domestic application, and diet, although the levels of exposure have generally been observed as low. Wind may carry the spray or contaminated soil into residential areas. People may also be exposed to glyphosate through the aquatic environment when the herbicide is intentionally applied to control aquatic weeds, is spilled, or is accidentally discharged.
Glyphosate binds tightly to soil, where it is eventually broken down by microbes. The half-life of glyphosate in the soil is an average of 47 days, but varies greatly between 2-197 days depending on local conditions. Glyphosate has a half-life of 3-91 days in water. It is thought to present a low risk of contaminating groundwater due to its strong absorptive properties; however it can contaminate surface waters through aquatic use and soil erosion. The general population may become exposed during active spraying. The low vapour pressure of glyphosate makes it unlikely to volatilize back into the air after being applied.
A Canadian National Water Quality Surveillance Program conducted in 2003-2005 found concentrations of glyphosate as high as 9,000 nanograms per litre (ng/L) in runoff water and 13,000 ng/L in surface water in the Lower Fraser Valley in BC. These levels are well below the maximum allowable concentration (MAC) for the Guidelines for Canadian Drinking Water Quality of 280,000 ng/L and the Canadian Council of Ministers for the Environment (CCME) Water Quality Guideline of 65,000 ng/L. Glyphosate was not detected in appreciable amounts in any of the other provinces tested.
The main routes of occupational exposure are dermal contact and inhalation.
CAREX Canada estimates that between 37,000 and 55,000 Canadian workers are exposed to glyphosate in the agricultural sector. Exposure among these workers occurs during the mixing, loading, and application of glyphosate, but many more may be exposed during other, farm-related activities through dermal contact with treated crops. Farm types with the largest number of exposed workers are other grain farming, oilseed farming, and dairy cattle and milk production (where glyphosate is applied on crops that are grown to feed livestock).
For more information, see the occupational exposure estimate for glyphosate.
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