Paraquat: The underestimated lethal pesticide.

ABSTRACT

Paraquat and diquat are popular herbicides which belong to the bipyridyl group. Paraquat was first synthesized in 1882, but began to be used as a herbicide only since the 1960s. It is available either in granular form or as water soluble concentrate which is an odourless brown liquid. The granular form is available as colourless crystals (dichloride salt) or a yellow solid (bis(methyl sulfate) salt). In India, most of the concentrates of paraquat are available as 10–20% solutions. Paraquat is a rapidly acting herbicide and kills the tissues of green plants mainly by contact action with foliage. Ingestion of paraquat by humans is associated with high mortality, which is a fact that is not widely recognized. Estimated lethal dose is just 10 to 15 ml of the concentrate. Ingestion of 20 to 40 mg of paraquat ion per kg body weight results in death in most cases. It is important to treat all cases of paraquat ingestion as potentially fatal poisonings.