Dicamba toxicity

There is little evidence of dicamba toxicity in mammals. In plants its primary action is to act as a growth regulator. 

This includes bioremediation cases of contaminated sites with several toxic and carcinogenic pollutants, such as petroleum hydrocarbons, PAHs, dichlorobenzene, chlorinated hydrocarbons, carbon tetrachloride, Dicamba, methyl bromide, trinitrotoluene, silicon-based organic compounds, dioxins, alkyl-phenol polyethoxylates, nonylphenol ethoxylates, and polychlorinated biphenyls. The following is a brief summary of each case. 

Bipyridyl herbicides include alachlor, amitrole, atrazine, bromacil, bromoxynil, butylate, cyanazine, dalapon, dicamba, diuron, linuron, fluometuron, hexazinone, molinate, metolachlor, oryzalin, pendimethalin pronamide, propanil, propazine, simazine, terbacil, triallate, and triclopyr. In addition to these herbicides, the most common bipyridyls are diquat and paraquat. Paraquat is more toxic than diquat and produces chronic abnormal cell growth in the lungs, cornea and lens of the eye, nasal mucosa, skin, and fingernails. Diquat affects the eye lens and intestinal tract lining, but does not usually produce the frequently fatal lung changes characteristic of paraquat. 

Little is known regarding chronic effects of dicamba in humans but animal studies suggest little potential for chronic toxicity. 

Low levels of an applied herbicide-pesticide-solvent mix were drawn into the uptake air of a commercial building following the application of a pesticide mix to the lawn in front of that building. Several employees immediately reported CNS and respiratory symptoms, with one sustaining a permanent respiratory injury. The pesticide mix applied to the lawn was composed of 2,4-D (2.82), 2-(2-methyl-4-chlorophenoxy) propionic acid (MCPP 2.48), and dicamba (2.21). The mixture also contained solvent naphtha (a mixture of aliphatic solvents, Kqw = 3.5-5.0) with 14% naphthalene (2.48) and dinitroaniline (3.30). The concentrations of all pesticides and solvents were far below the TLVs both outside and inside the building. The toxic effects observed were ascribed to the mixture of lipophilic and hydrophilic pesticides. 441... 

The pesticides chIorpyrifos, ,4-D acid, 2,4-DP acid, dicamba, dinoseb, and propaniI were positive in the bacterial relative toxicity assays (propaniI in B. subtiI is only), but in all other assays, produced no activity (Table IV). Increased mitotic recombination was induced by azinphos-methyI, crotoxyphos, cacodylic acid, and parathion-methyl in cerevisiae D3 disulfoton enhanced UDS in WI-38 cells. As shown in Table V, however, these pesticides produced no other effects. Bromacil and simazine were positive only in the Drosophila sex-linked recessive lethal test (Table VI). 

Fig. 8 Degradation pathway, physicochemical descriptors, and toxicity model of dicamba. Physicochemical properties are from (a) experimental value from Episuite [39], (b) estimated values from Episuite [39], (c) [44], (d) [49]...

Fig. 9 Fractions of metabolites formed, fi, and toxic potential of the metabolites, TPf, and the mixture, TPmixturo for dicamba. Bars correspond to the average between TPf, min and TPf, max and the error bars indicate the range between min and max. If there is no error bary the mode of action is either known or baseline toxicity applies...

Toxicity LC50 (96-hour) for rainbow trout and bluegill sunfish 135 mg/L (Hartley and Kidd, 1987) LCjo (48-hour) for bluegill sunfish 20.0 mg/L (Verschueren, 1983), for Daphnia magna 110.7 mg/L, for grass shrimp >100.0 mg/L, for both sheaps-head minnow and fiddler crab >180.0 mg/L (Humburg et al., 1989) acute oral LD,o of technical dicamba for rats 1,700 mg/kg (Ashton and Monaco, 1991), pure dicamba 1,039 mg/kg (RTECS, 1985). 

PiLLAY and Tchan (1972) observed that bromacil was more toxic to Chlorella NMI than were the triazines, atrazine, simazine, and atratone only 0.32 ppm was required for 50% inhibition of the growth of the alga. Cullimore (1975), in an extensive study of the influence of a range of herbicides (diuron, monuron, and linuron paraquat and diquat bromacil 2,4-DB, 2,4-DP, and 2,4,5-T barban and EPTC dicamba and 2,3,6-TBA dichlobenil and bromoxynil dalapon picloram) on 17 members of the Chlorophyceae, established bromacil to be one of the most toxic of these herbicides. Most sensitive of the algal genera were Hormid-ium and Haematococcus. 

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