"Paraquat pot"
During the late 1970s, a controversial program sponsored by the US government sprayed paraquat on marijuana fields in Mexico.[8] Since much of this marijuana was subsequently smoked by Americans, the US government's "Paraquat Pot" program stirred much debate. Perhaps in an attempt to deter people from using marijuana, representatives of the program warned that spraying rendered the crop unsafe to smoke.However, independent bodies have studied paraquat in this use. Jenny Pronczuk de Garbino,[9] stated: "no lung or other injury in marijuana users has ever been attributed to paraquat contamination". Also a United States Environmental Protection Agency manual states: "... toxic effects caused by this mechanism have been either very rare or nonexistent. Most paraquat that contaminates marijuana is pyrolyzed during smoking to dipyridyl, which is a product of combustion of the leaf material itself (including marijuana) and presents little toxic hazard."[10]
[edit] In suicide
A large majority (93%) of fatalities from paraquat poisoning are cases of intentional self-administration, i.e., suicides. In third world countries, paraquat is a "major suicide agent".[11] For instance, in Samoa from 1979-2001, 70% of suicides were by paraquat poisoning. In southern Trinidad from 1996-1997, 76% of suicides were by paraquat.[12]The reason paraquat is such a widely used suicide agent in third-world countries is due to its widespread availability, low toxic dose (10 ml or 2 teaspoons is enough to kill) and relative low cost. There are campaigns to control or even ban paraquat outright, and there are moves to restrict its availability by requiring user education and the locking up of paraquat stores.
[edit] Toxicity
Pure paraquat, when ingested, is highly toxic to mammals, including humans; potentially leading to acute respiratory distress syndrome (ARDS), and there are no specific antidotes. However, fuller's earth or activated charcoal is an effective treatment, if taken in time. Death may occur up to 30 days after ingestion. Diluted paraquat used for spraying is less toxic; thus, the greatest risk of accidental poisoning is during mixing and loading paraquat for use.[3]In acute toxicity studies using laboratory animals, paraquat has been shown to be highly toxic by the inhalation route and has been placed in Toxicity Category I (the highest of four levels) for acute inhalation effects. However, the EPA has determined that particles used in agricultural practices (400 to 800 μm) are well beyond the respirable range and therefore inhalation toxicity is not a toxicological endpoint of concern. Paraquat is toxic (Category II) by the oral route and moderately toxic (Category III) by the dermal route. Paraquat will cause moderate to severe eye irritation and minimal dermal irritation, and has been placed in Toxicity Categories II and IV (slightly toxic) respectively for these effects.[13]Even a single swig, immediately spat out, can cause death from fibrous tissue developing in the lungs, leading to asphyxiation.[14]
According to the Center for Disease Control, ingesting paraquat causes symptoms such as liver, lung, heart, and kidney failure within several days to several weeks that can lead to death up to 30 days after ingestion. Those who suffer large exposures are unlikely to survive. Chronic exposure can lead to lung damage, kidney failure, heart failure, and oesophageal strictures.[15] Accidental deaths and suicides from paraquat ingestion are relatively common. For example, there have been 18 deaths in Australia from paraquat poisoning since 2000.[16]
Paraquat-induced toxicity in rats has also been linked to Parkinson's-like neurological degenerative mechanisms.[17] A study by the Buck Institute showed a connection between exposure to paraquat and iron in infancy and mid-life Parkinson's in laboratory mice.[18]
Long term exposures to paraquat would most likely cause lung and eye damage, but reproductive/fertility damage was not found by the EPA in their review. Some suspect a possible link to a greater incidence of Parkinson's disease.
