2,4-Dichlorophenoxyacetic acid toxicity

Toxicity of six toxicants (Zn2+ > ethidium bromide > sodium pentachloro- 208 phenate > Cu2+ > 2,4-dichlorophenoxyacetic acid sodium dodecyl sulfate = no) on a recombinant Escherichia coli Toxicity of metals in soils amended with sewage sludge 209... 

Drill VA, Hiratzka T Toxicity of 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid. AMA Arch Ind Hyg Occup Med 7 61-67, 1953... 

Dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), and their salts and esters are compounds of interest as herbicides used for the destruction of weeds (Figure 56-1). They have been assigned toxicity ratings of 4 or 3, respectively, which place the probable human lethal dosages at 50-500 or 500-5000 mg/kg, respectively. 

US Environmental Protection Agency (2005) 2, 4-D (2,4-Dichlorophenoxyacetic Acid) Reregistration Eligibility Decision (RED) Document, document number EPA 738-R-05-002, US Environmental Protection Agency Office of Prevention, Pesticides and Toxic Substances, Washington, DC. 

T (2,4,5-trichlorophenoxyacetic acid) ester formulation to a complex mixture of successively less-chlorinated phenoxyacetic esters, and Que Hee, et al. (16) reported a similar dechlorination of 2,4-D (2,4-dichlorophenoxyacetic acid). The toxic 2,4,5-T impurity, TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin), was dechlo-rinated in a herbicide ester deposit on a sunlit leaf surface within a few hours (Figure 5) (17). 

There are other herbicides in use which cannot be discussed in detail here, but one particular pair of chemicals should be mentioned. These are 2,4-D and 2,4,5-T, which are abbreviations of 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid. These chemicals act like plant growth hormones but cause excessive growth. They are selectively toxic against weeds. Although these herbicides have low toxicity to animals they can be contaminated with the most toxic type of dioxin (2,3,7,8-TCDD), as a result of the manufacturing process. The mixture of 2,4-D and 2,4,5-T was... 

Charles JM, Dalgard DW, Cunny HC, Wilson RD, and Bus JS (1996) Comparative subchronic and chronic dietary toxicity studies on 2,4-dichlorophenoxyacetic acid, amine, and ester in the dog. Fundamental and Applied Toxicology 29(1) 78-85. 

Rowland J (1996) 2,4-Dichlorophenoxyacetic Acid Review of a Chronic Toxicity/Carcinogenicity Study in Rats A Carcinogenicity Study in Mice, and a Re-review of a Developmental Toxicity Study in Rats, EPA Memorandum. 

Agent Orange. A toxic herbicide and defoliant containing 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and 2,4-dichlorophenoxyacetic acid (2,4-... 

Arle, Leonard, and Harris80 reported the use of activated carbon to protect sensitive field crops against injury from a weed killer— 2,4-D (2,4-dichlorophenoxyacetic acid). In one of several experiments, a field was sprayed with 2,4-D—1.3 pounds free acid equivalent per acre. One-half of the plot was planted with sweet-potato sprouts that had been previously moistened and then dusted with activated carbon the other half of the plot was planted with untreated sprouts. In the case of the untreated sprouts, only 2.5% survived whereas 95.0 % of the sprouts treated with activated carbon survived and produced plants that were normal in every respect. Weaver81 found that the toxic effect of 2,4-D on soybean, red kidney bean, white mustard, or marigold were eliminated or decreased by dusting or spraying activated carbon in aqueous suspension on the plants before the 2,4-D treatment. 

Schulze, G. E., and J. A. Dougherty. 1988. Neu-robehavioral toxicity and tolerance to the herbicide 2,4-dichlorophenoxyacetic acid n-butyl ester (2,4-D ester). Fundam. Appl. Toxicol. 10(3) 413-24. 

Chlorophenoxy compounds have been widely used as herbicides. Agent Orange was a mixture of the chlorophenoxy herbicides 2,4-D (dichlorophenoxyacetic acid) and 2,4,5-T (trichlorophenoxyacetic acid) that also contained small amounts of the highly toxic contaminant TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin see p 184) derived from the process of manufacturing 2,4,5-T. Manufacture ot 2,4-D by chlorination of phenol does not produce TCDD. Populations involved in manufacture or handling of 2,4,5-T may show elevated levels of TCDD on serum testing and overall increased rates of cancer compared to the general population. 

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