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. There are three commercially available formulations, salt, amine, and ester, each with slightly different properties. Commercial names for products containing 2,4-D include Aqua-Kleen, Barrage, Lawn-Keep, Malerbane, Planotox, Plantgard, Savage, Salvo, Weedone, and Weedtrine-II. There are numerous other synonyms and product names; see HSDB for more information.
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. 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.
Other reported health effects of acute exposure to 2,4-D include fatigue, weakness, and digestive problems.
stel = short term exposure limit (15 min. maximum)
Canadian Environmental Guidelines
Canadian Drinking Water Guidelines
0.1 mg/L (MAC)
Maximum Residue Limits for Foods
Asparagus: 5 ppm Citrus fruits: 2 ppm Cranberries: 0.5 ppm All other fruits: 0.05 ppm
MAC = Maximum Allowable Concentration
ppm = parts per million
DSL – high priority substance with lowest potential for exposure
2,4-D was not included in other Canadian government chemical listings reviewed.[9,19]
2,4-D is the most widely used herbicide in the world, and the third most widely used in North America. It was developed and introduced in 1946 as the first successful selective herbicide, controlling weeds without damaging the crop.
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. Typically a general use herbicide, 2,4-D may also be mixed with other pesticides or fertilizers.
Canadian Production and Trade
Although Canada engages in international trade of herbicides, specific formulations are not listed in TradeMap.
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). A 2004 industry report forecasted that demand for 2,4-D in 2006 was expected to reach 3,000 tonnes.
Inhalation and dermal absorption are the most important routes of occupational exposure. Workers most commonly exposed are farmers/farm workers and lawn care workers, especially those who apply the pesticides, as well as workers involved in pesticide manufacture. Several studies conducted in Ontario have quantitatively measured exposure to 2,4-D in farmers.[24,25,26]
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. 2,4-D may remain active against susceptible plants for up to 4 weeks post-application. 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.
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.
Children playing in treated parks and lawns may take home 2,4-D on the bottom of shoes and feet. 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. Like most pesticides, 2,4-D persists longer indoors than outdoors.
Release of 2,4-D is not reportable to Environment Canada's National Pollutant Release Inventory. A search of the US Household Products Database for 2,4-D yielded the following results:
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
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.