Trade name for an organic herbicide, 1,1′-dimethyl-4,4′-bipyridinium dichloride, used to control broadleaved weeds and grasses (see viologen dyes). It is poisonous to humans, having toxic effects on the liver, lungs, and kidneys if ingested. Paraquat is not easily broken down and can persist in the environment adsorbed to soil particles. It is prohibited in the European Union. See also pesticide.