2,4-D
Full Profile
General Information
2,4-D is a colourless or white crystalline powder or flakes used as a systemic herbicide to control broadleaf weeds.[1,2] 2,4-D may also be referred to by its full chemical name, 2,4-dichlorophenoxyacetic acid.
2,4-D is classified by the EPA as a herbicide, a plant growth regulator, and a fungicide.[3] There are three commercially available formulations, salt, amine, and ester, each with slightly different properties.[4] Commercial names for products containing 2,4-D include Aqua-Kleen, Barrage, Lawn-Keep, Malerbane, Planotox, Plantgard, Savage, Salvo, Weedone, and Weedtrine-II.[3] There are numerous other synonyms and product names; see HSDB for more information.[1]
Chlorophenoxy herbicides, including 2,4-D, have been classified by IARC as Group 2B, possibly carcinogenic to humans, on the basis of limited evidence in human and insufficient evidence in experimental animals.[5] While the epidemiological studies reviewed by IARC suggested associations between exposure to the chlorophenoxy herbicides and both non-Hodgkin's lymphoma and bronchial sarcoma, the studies had limitations.[5]
Other reported health effects of acute exposure to 2,4-D include fatigue, weakness, and digestive problems.[4]
2,4-D has been ranked by CAREX Canada as Group A (immediate high priority) for both the occupational and environmental settings. Prioritization was based on the carcinogenicity and other toxic properties of the substance, the prevalence of exposure in Canada, and the feasibility of assessing exposure.
Regulations and Guidelines
Occupational Exposure Limits (OEL)
| Canadian Jurisdictions | OEL (mg/m3) |
|---|---|
| Canada Labour Code | 10 |
| AB, MB, ON, QC, NL, NB, NS, PE | 10 |
| BC, SK, YT, NT, NU | 10 20 [stel] |
| Other Jurisdiction | OEL (mg/m3) |
| ACGIH 2011 TLV | 10 |
Canadian Environmental Guidelines
| Jurisdiction | Limit | Year |
|---|---|---|
| Canadian Drinking Water Guidelines | 0.1 mg/L (MAC) | 2010[6] |
| Maximum Residue Limits for Foods | Asparagus: 5 ppm Citrus fruits: 2 ppm Cranberries: 0.5 ppm All other fruits: 0.05 ppm |
2011[7] |
Canadian Agencies/Organizations
| Agency | Designation/Position | Year |
|---|---|---|
| Health Canada | DSL – high priority substance with lowest potential for exposure | 2006[8] |
2,4-D was not included in other Canadian government chemical listings reviewed.[9,19]
Main Uses
2,4-D is the most widely used herbicide in the world, and the third most widely used in North America.[12] It was developed and introduced in 1946 as the first successful selective herbicide, controlling weeds without damaging the crop.[12]
Major agricultural applications include wheat and small grains, sorghum, corn, rice, sugar cane, low-till soybeans, rangeland, and pasture. It may also be used on roadsides, non-crop areas, forestry, home lawn & turf care, and on aquatic weeds.[12] Typically a general use herbicide, 2,4-D may also be mixed with other pesticides or fertilizers.[13]
Canadian Production and Trade
Although Canada engages in international trade of herbicides, specific formulations are not listed in TradeMap.[20]
There is no domestic production of 2,4-D in Canada; imports in 2003 were 2,760 tonnes (mostly from the United States, and in the form of amines and esters of 2,4-D).[21] A 2004 industry report forecasted that demand for 2,4-D in 2006 was expected to reach 3,000 tonnes.[21]
Occupational Exposures
Inhalation and dermal absorption are the most important routes of occupational exposure.[1] Workers most commonly exposed are farmers/farm workers and lawn care workers, especially those who apply the pesticides,[22] as well as workers involved in pesticide manufacture.[23] Several studies conducted in Ontario have quantitatively measured exposure to 2,4-D in farmers.[24,25,26]
Environmental Exposures
2,4-D is released into the environment as the result of human activities. Sources of exposure include aerial drift from field spray and contaminated water, food and soil.[12] 2,4-D may remain active against susceptible plants for up to 4 weeks post-application.[23] The half-life for biodegradation of 2,4-D ranges from a few days to 6 weeks in soil and from one to several weeks in water.[27]
Environmental exposure to 2,4-D can occur through consumption of contaminated food and drinking water from both surface and groundwater sources, incidental ingestion of contaminated soil and dust, and inhalation.[3]
Children playing in treated parks and lawns may take home 2,4-D on the bottom of shoes and feet.[28] Children whose parents work with agricultural pesticides, or who live in agricultural areas may be at risk of higher exposure to pesticides than other children.[29] Like most pesticides, 2,4-D persists longer indoors than outdoors.[28]
Release of 2,4-D is not reportable to Environment Canada's National Pollutant Release Inventory.[30] A search of the US Household Products Database for 2,4-D yielded the following results:
US Household Products Database
| US Household Products 2010[31] | ||
|---|---|---|
| Search Term | Quantity | Product Type |
| 2,4-D | 24 | Home use herbicides and pesticides |
Sources
- Wikimedia Commons Photo: 2,4-Dichlorophenoxyacetic acid
- Chapter 9 ('Chlorophenoxy Herbicides') of "Recognition and Management of Pesticide Poisonings", 5th edition. EPA document #735-R-98-003, March 1999. (PDF)
- EPA: Re-registration Eligibility Decisions for 2,4-D (2005) (PDF)
- NPIC Fact sheet for '2,4-D' (PDF)
- IARC monograph summary, Volume 41, Suppl. 7 (1987) (PDF)
- Health Canada (2010) Guidelines for Canadian Drinking Water
- Maximum Residue Limits for Pesticides, Health Canada (2011)
- Health Canada's Prioritization of the DSL (2006)
- CEPA List of Toxic Substances (1999)
- Statistics Canada Summary: Private Property Pesticide By-Laws in Canada. Population Statistics by Municipality (2008) (PDF)
- Health Canada 2008. Questions and Answers: Final Decision on the Re-evaluation of 2,4-D
- Industry Task Force II on 2,4-D Research Data
- Extension Toxicology Network (EXTOXNET) Pesticide Information Profiles: 2,4-D (1996)
- PMRA: 2,4-D Re-evaluation Update and Label Improvement Program (1994)
- Industry Research Task Forces for Phenoxy Herbicides (MCPA, 2,4-D, and mecoprop-p). Prepared by RIAS Inc 'Assessment of Economic and Related Benefits to Canada of Phenoxy Herbicides' (2006) (PDF)
- Ministry of the Environment, Survey of Pesticide Sales and Use in BC (1999) (PDF)
- BC Ministry of the Environment, Survey of Pesticide Use in BC (2003) (PDF)
- Ontario Ministry of Agriculture and Food, Survey of Pesticide Use in Ontario, 2003 (2004)
- Government of Canada (2010) Chemicals Management Plan – List of all Challenge Substances
- TradeMap (Free subscription required)
- CPI Product Profiles, Camford Information Services: 2,4-Dichlorophenoxyacetic Acid (2004)
- Stephenson, G.R. et al (Revised 2002). Environmental Persistence and human exposure studies with 2,4-D and other turfgrass pesticides. Centre for Toxicology, University of Guelph, Ontario (PDF)
- Health Canada: Health Canada Agency Investigates Assess the Risk of Pesticides
- Arbuckle, T.E. et al. Predictors of herbicide exposure in farm applicators. International Archives of Occupational and Environmental Health. 2002; 75(6): 406-414.
- Arbuckle, T.E. et al. Biomonitoring of herbicides in Ontario farm applicators. Scandinavian Journal of Work, Environment and Health. 2005; 31 Supplement 1: 90-97; Discussion 63-5.
- Arbuckle, T.E. 2,4-Dichlorophenoxyacetic acid residues in semen of Ontario farmers. Reproductive Toxicology. 1999; 13(6):421-429.
- WHO Guidelines for Drinking-Water Quality, Second Edition, Volume 1: Recommendations (1993) (PDF)
- Basrur, S.V. Lawn and Garden Pesticides: A Review of Human Exposure and Health Effects Research. Toronto Public Health 2002 (PDF)
- Lu C, et al (2000). 'Pesticide exposure of children in an agricultural community: evidence of household proximity to farmland and take home exposure pathways.' Environmental Research, Vol. 84, Issue 3, pp 290-302
- The National Pollutant Release Inventory
- Household Products Database (US)
Other Resources
- Pest Management Regulatory Agency (PMRA): Responsible Pesticide Use (2,4-D Uses)
- PMRA: Fact Sheet on the Regulation of Pesticides in Canada (PDF)
- WHO: Developing Human Health-related Chemical Guidelines for Reclaimed Waster and Sewage Sludge: Applications in Agriculture, (2001) (PDF)
- World Health Organization, International Programme on Chemical Safety. (1989). Environmental Health Criteria 84. 2,4-Dichlorophenoxy acetic acid-Environmental Aspects. Geneva, Switzerland: World Health Organization.