ENVIRONMENTAL FATE AND EFFECTS OF MCPA - A CANADIAN PERSPECTIVE

A review of the environmental chemistry, fate, and toxicology of the herbicide MCPA was conducted. MCPA is used worldwide and is among the top ten herbicides sold in Canada. It has a systemic effect and is used to control a large range of broadleaf weeds in agricultural and noncrop lands. MCPA is highly water soluble and has a low affinity for most soil types, which gives it the potential to leach and contaminate groundwaters. It can undergo microbial degradation in aerobic conditions; therefore, it is only slightly persistent in soil and water. In Canada, MCPA has been detected in surface waters at levels varying between 0.00003 and 0.013 mg/l, and at relatively high levels in some groundwater (1.0 mg/l). It has also been reported to affect organisms such as the diatom Navicula pelliculosa at levels as low as of 0.026 mg/l, and the beagle dog at concentrations of 0.75 mg/kg/d. This review includes the development of the Canadian Water Quality Guidelines for MCPA, which are numerical concentrations of MCPA designed to protect freshwater and marine water life, livestock, and crops.