About dicamba : Health Effects

Dicamba is readily and almost completely absorbed by the gastrointestinal tract. Metabolism in rats is rapid, with 70% of the dose excreted unchanged in the urine in five hours, and most of the remainder within three days. Dicamba has a fairly low acute toxicity.4 Its principal toxic action is on the liver, with vacuolization, necrosis, fatty deposits and liver weight changes noted at high doses in rats and dogs.4 In a subchronic (15-week) study, male Wistar rats were administered technical dicamba in the diet at doses equivalent to 0, 3.8, 12, 37, 119 or 364 mg/kg bw per day. A no-observed-adverse-effect level (NOAEL) of 37 mg/kg bw per day was observed, based on increases in relative liver/body weight ratios at doses of 119 and 364 mg/kg bw per day. In a 13-week study, male and female Sprague-Dawley rats were administered technical dicamba, in a formulation with dimethylamine, in the diet at doses equivalent to 41, 206, 330 and 413 mg dicamba per kilogram diet per day. At the highest dose, 413 mg/kg in the diet or about 21 mg/kg bw per day, necrosis and vacuolization of the liver were seen. The NOAEL for effects on the liver was 206 mg dicamba per kilogram diet or approximately 10 mg/kg bw per day (unpublished study, cited in reference 4). Sprague-Dawley rats (32 per sex per dose) were administered technical dicamba in the diet at doses equivalent to 0, 0.25, 2.5, 5, 12.5 or 25 mg/kg bw per day for two years. No differences in survival, body weight, food consumption, organ weights or histology were noted at any dose, but the data presented were insufficient to allow estimation of a NOAEL. In a two-year study in which dogs (three per sex per dose) were administered technical dicamba in the diet at doses equivalent to 0, 0.125, 0.625 or 1.25 mg/kg bw per day, a decrease in body weight was observed in males at 0.625 and 1.25 mg/kg bw per day, with a NOAEL at 0.125 mg/kg bw per day. There were no compound-related effects on survival, food consumption, haematology, urinalysis or organ weights. No data were presented on gross pathology or histology of organs other than heart, lung, liver and kidney. No compound-related increases in tumour incidence were observed in the two-year dog study or the two-year rat feeding study, although it should be pointed out that these studies were inadequate to allow evaluation of the potential of dicamba as a carcinogen. Dicamba was not mutagenic in several microbial test systems, including the Ames/Salmonella test. Further short-term tests are required for mammalian test systems, chromosome aberrations and DNA repair studies. In a three-generation rat study in which CD rats (20 females and 10 males per dose) were fed dicamba at doses equivalent to 0, 0.25, 2.5, 5, 12.5 or 25 mg/kg bw per day, there were no effects on fertility, viability or pup development. No teratogenic or foetotoxic effects were noted in albino rats administered technical dicamba by gavage on days 6 to 19, at doses up to 400 mg/kg bw per day, the highest dose tested. New Zealand white rabbits were administered technical dicamba per os at doses of 0, 0.5, 1, 3, 10 or 20 mg/kg bw on days 6 to 18 of pregnancy. A NOAEL of 3 mg/kg bw per day was observed, based on reductions in both foetal and maternal body weights and increased post-implantation losses at 10 or 20 mg/kg bw per day. There were no teratogenic effects.  Yangzhou pioneer chemical CO.,LTD