Q. Is it safe to smoke marijuana that has been sprayed with paraquat?

A. In the late 1960’s the US government, perhaps in an attempt to deter people from using marijuana, warned that much of the crop had been sprayed with paraquat and was thus unsafe to smoke.
However, independent bodies have studied paraquat in this use. Jenny PronCzuk de Garbino1 stated: "no lung or other injury in marijuana users has ever been attributed to Paraquat contamination".
On this topic, D.P. Morgan states in a US Environmental ProtectionAgency publication that: "Smoking Paraquat-contaminated marijuana does not result in lung damage as the herbicide is pyrolyzed to dipyridyl (which does not present a toxic hazard) during smoking" 2.
The manufacturers of paraquat market the herbicide to kill green weeds and do not control on which weeds customers decide to use it. For more information on the uses of paraquat in agriculture, visit the Use section of this site to read various case studies.


  1. Jenny PronCzukde Garbino Epidemiology of Paraquat Poisoning International Programme on chemical safety WHO-Geneva-Book-Paraquat Poisoning.
  2. Dr J Routt Reigart, Dr James R Robert 1999 Paraquat and Diquat Recognition and Management of Pesticide Poisonings 5th edition US Environmental Protection Agency 1999.
For more information see: http://www.epa.gov/pesticides/safety/healthcare/handbook/Chap12.pdf Note: The Paraquat Information Center reports the facts and does not endorse the use of any illegal drugs.