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Dichlorprop-p

Lead Editor

Overview


Dichlorprop is a chlorophenoxy class herbicide. It is also known as 2,4-DP because of its chemical similarities to 2,4-D. It was first registered with the EPA in the 1960s. 2,4-DP is composed of two dichlorprop chemical isomers, one of which is inactive as an herbicide. In the 1980s, new technologies allowed companies to produce higher concentrations of the active dichlorprop isomer. This chemical was named dichlorprop-p, or 2,4-DP-p, and has essentially replaced the 2,4-DP formulation (#EPA).

Dichlorprop is used to control broadleaf weeds and brush. It is not used near any food-producing plants. It is most commonly used in residential lawn applications.

Chemical Description


2,4-DP-p is a white solid with a strong odor (#EPA). 2,4-DP is a colorless to yellow crystal with no odor. It is not soluble in water (#NIOSH) although some chemical variants of 2,4-DP-p are soluble. It does not bond strongly with soil. Dichlorprop-p has a half-life of 35 days (#EPA).

Dichlorprop-p is available in granular formulations, emulsifiable concentrates, wettable powders, and ready-to-use solutions (#EPA).

Uses


Dichlorprop targets post-emergent broadleaf weeds and brush (both annuals and perennials). It is used for weed control on residential lawns, recreational turf, sports fields, sod farms, roadsides, industrial sites, rights-of-way, and forests. The United States uses roughly 4 million pounds of dichlorprop-p annually. An estimated 60% of this is used on residential lawns (#EPA). It is not used in agricultural applications.

Human Health Effects


2,4-DP and 2,4-DP-p have been found to have very similar levels of toxicity, and are metabolized into the same products. Dichlorprop generally has a low acute toxicity in oral, dermal, and inhaled routes of exposure. However, it is a corrosive eye irritant (#EPA). The EPA believes that dichlorprop is an unlikely carcinogen, and also listed it as a developmental toxin in its Toxics Release Inventory(#PANNA). A study in which dogs were fed 2,4 DP for 12 months found no significant changes in food consumption, urinalysis, or organ weight. Diarrhea was observed in higher doses (#NLM).

If ingested, dichlorprop may cause diarrhea, headache, nausea, and vomiting (#PANNA).

Environmental Health Effects


In plants, dichlorprop increases cell wall plasticity and stimulates synthesis of proteins and ethylene, a plant hormone. This results in abnormal growth which damages vascular and growing tissues, ultimately resulting in death (#EPA).

Dichlorprop is only slightly toxic to mammals. The oral LD50 in rats is 567 mg/kg. It is a mild skin irritant to rabbits. Dichlorprop has a moderate toxicity to birds. The oral LD50 in Bobwhite quail is 242 mg/kg. To fish and other marine organisms, dichlorprop ranges from non-toxic to moderately toxic (#EPA).

Accumulation of dichlorprop in the food chain is not considered a significant threat (#NLM). Considering its solubility (in some forms), and its low affinity for soil, dichlorprop can contaminate water sources in runoff (#EPA).

Regulation


Dichlorprop is registered for general use, but it is not registered for use on any agricultural food crop. Due to the potential mobility of dichlorprop, the EPA banned the use of aerial applications (#EPA).

Precautionary Notes


If burned or heated, dichlorprop releases toxic or corrosive gasses (#NIOSH). Do not use dichlorporp near any food sources.

References



Environmental Protection Agency. Reregistration Eligibility Decision for Dichlorprop. (August 2007). http://www.epa.gov/opp00001/reregistration/REDs/24dp_red.pdf [Accessed 7-20-10].


National Institute for Occupational Safety and Health. Dichlorprop. http://www.cdc.gov/niosh/ipcsneng/neng0038.html [Accessed 7-20-10].


National Library of Medicine: Toxicology Data Network. Dichlorprop. http://toxnet.nlm.nih.gov/cgi-bin/sis/search/f?./temp/~4GfUIT:1 [Accessed 7-20-10].


Pesticide Action Network North America. Dichlorprop. http://www.pesticideinfo.org/Detail_Chemical.jsp?Rec_Id=PC33424 [Accessed 7-20-10].

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