ABSTRACT
The dimethylamine salt of 2,4-dichlorophenoxyacetic acid (2,4-D DMA) is used as a broadleaf herbicide on a variety of crops and on range, pasture, and parkland. In environmental fate studies for 2,4-D DMA, the disappearance of the free acid, 2,4-D rather than the dimethylamine salt is generally monitored. 2,4-D DMA has a very high water solubility and low vapor pressure, indicating that the Henry’s Law constant and rate of evaporation from water will be low. 2,4-D DMA is rapidly degraded by aquatic microorganisms in activated sewage at about the same rate as the free acid. 2,4-D and its derivatives can be absorbed via the oral, dermal, and inhalation routes. A half-life of 3.9 days was obtained for an unspecified amine salt of 2,4-D in a river die-away study. General population exposure is mainly by the oral route due to consumption of contaminated foods, but under occupational and bystander exposure conditions, the dermal route is by far the most important.
