Bentazon is an herbicide used in agriculture for selective postemergence control of many broadleaf weeds in soybeans, rice, corn, peanuts, mint, dry beans, dry peas, and succulent lima beans. 
Bentazon is expected to enter surface water by run of from application sites. It has a moderate water solubility of 500 mg/l and a low tendency to adsorb to soils and sediments. In water it can be rapidly broken down by sun light. It can take between 24 hours and 4 moths to half its concentration depending on the environmental conditions. It can also be biodegraded.  
It has a very low a tendency to bioaccumulate.
Bentazon has a low toxicity to most aquatic animals. Concentrations above 100 mg/l are necessary to cause toxicity in fishes. Invertebrates are most vulnerable; mussels die at concentrations above 20 mg/l. Concentrations above 5 mg/l might affect phytoplankton. 
Environmental standards and legislation