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]
How did CAREX choose this agent for review?
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.