Picloram toxicity

U.S. Environmental Protection Agency, Guidance for the Reregistration of Pesticide Products Containing Picloram as the Active Ingredient, Office of Pesticides and Toxic Substances, Washington, DC, EPA Publication No. 540/RS-88-132, 1988. 

Little is known about the mechanism of toxicity of picloram. 

Lifetime daily exposure of rats and dogs to diets containing 150 mg kg body weight doses of picloram resulted in no observable gross or microscopic signs of toxicity. A 6 month dog study at doses as... 

Because of a lack of information for humans and animals, picloram is not classifiable with regard to its carcinogenicity in humans according to the lARC and the ACGIH. Little or no data is available relating to the chronic toxicity of picloram. 

Multigeneration studies in rats dosed orally at 15 mgkg day did not have any effect on fertility, whereas rats showed no effects when dosed up to ISOmgkg day. Picloram does not appear to cause reproductive toxicity. 

Picloram is a slightly toxic compound in EPA toxicity class III and products containing it must bear the signal word CAUTION on the label. 

Picloram is of low toxicity to mammals, its acute oral LDg for rats is 8200 mg/kg. It has no teratogenic effect. 

The toxic effects from ingestion or inhalation of dusts of picloram in test animals... 

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. 

Surfactant effects on adsorption of herbicides on to soil have been investigated and suggested to be a factor to be considered in the overall effect of surfactant on toxicity towards the plant. The degradation, mobility and uptake of one such compound, picloram [4-amino-3,5,6-trichloropicolinic acid] (pK = 3.4) is affected by adsorption-desorption processes in solids. Picloram adsorption on to soils at pH 5 was reduced by 1 % anionic surfactant [284]. The mechanism involved in picloram adsorption included protonation of the molecule, metal-ion bridging and interaction with metal ions. Picloram adsorption was enhanced by cationic surfactants, suggesting that hydrophobic adsorption of the cationic monomers on to the soil provides a cationic surface for interaction of the anionic picloram. Different soils with different pH values resulted in some variations in these effects which are presented in Table 10.29. 

A.G.S. Prado, C. Airoldi, Toxic effect caused on microflora of soil by pesticide picloram application. J. Environ. Monit. 3, 394-397 (2001). doi 10.1039/bl03872a... 

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