Photo: Grain fields (possibly barley), Driggs, Idaho. Copyright 2020, Delena Norris-Tull
Paraquat Dichloride
Summary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, 2023.
Paraquat dichloride is a highly toxic herbicide. It was introduced in the US for the control of broadleaf weeds and grasses in 1961. It is still widely used and is the active agent in a large number of herbicide brands, including Gramoxone, Firestorm, Helmquat, and Parazone. In 2021, the EPA has reviewed its potential danger to human health and continues to support its restricted use as a herbicide. The European Union banned the use of paraquat as an herbicide in 2007.
In addition to dangers to human health if accidentally ingested or inhaled or exposed to the skin, paraquat also can cause damage to other animals and plants due to wind drift. At the current time, the EPA has concluded that there is no clear evidence that use of paraquat causes Parkinson’s or cancers in humans. The 2021 EPA assessment is considered to be an interim decision on its use. In the US, this herbicide can only be applied by trained users.
There is currently a multi-district litigation (similar to a class action lawsuit) in process, against Syngenta (which manufactures Gramoxone) and Chevron (which distributes the product in the USA). There are over 2000 individuals who claim that paraquat has caused Parkinson’s or other diseases in individuals working in the manufacture or use of paraquat. But the research on these links are mostly unsubstantiated at this time.
In the 1970s, the Mexican government sprayed paraquat on marijuana farms, to stop the illegal growing of marijuana. The US Congress learned of this use in 1978 and tasked the Centers for Disease Control (CDC) and the National Institute of Environmental Health Sciences (NIEHS) to assess the likely risks to the health of individuals who smoke paraquat drenched marijuana. While the survey of those individuals who reported lung symptoms did not verify that paraquat poisoning had caused chronic or acute lung damage, the report concluded that smoking paraquat laced marijuana has a clear potential for lung damage (Landrigan, Powell, James, & Taylor, 1983). In addition, the assessment revealed that from 1975-1978, the US Government had indirectly funded not only the spraying of paraquat on marijuana farms, but also the spraying of the herbicide 2,4-D on poppy fields, in an attempt to slow down the opium industry.
While the US stopped funding the use of paraquat spraying on marijuana fields in Mexico, in the 1980s, the Reagan Administration funded the spraying of paraquat on marijuana fields in Georgia. Various lawsuits finally ended this practice in the 1990s (Legal Examiner, 2021).
References for this section
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Paraquat Dichloride
Summary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, 2023.
Paraquat dichloride is a highly toxic herbicide. It was introduced in the US for the control of broadleaf weeds and grasses in 1961. It is still widely used and is the active agent in a large number of herbicide brands, including Gramoxone, Firestorm, Helmquat, and Parazone. In 2021, the EPA has reviewed its potential danger to human health and continues to support its restricted use as a herbicide. The European Union banned the use of paraquat as an herbicide in 2007.
In addition to dangers to human health if accidentally ingested or inhaled or exposed to the skin, paraquat also can cause damage to other animals and plants due to wind drift. At the current time, the EPA has concluded that there is no clear evidence that use of paraquat causes Parkinson’s or cancers in humans. The 2021 EPA assessment is considered to be an interim decision on its use. In the US, this herbicide can only be applied by trained users.
There is currently a multi-district litigation (similar to a class action lawsuit) in process, against Syngenta (which manufactures Gramoxone) and Chevron (which distributes the product in the USA). There are over 2000 individuals who claim that paraquat has caused Parkinson’s or other diseases in individuals working in the manufacture or use of paraquat. But the research on these links are mostly unsubstantiated at this time.
In the 1970s, the Mexican government sprayed paraquat on marijuana farms, to stop the illegal growing of marijuana. The US Congress learned of this use in 1978 and tasked the Centers for Disease Control (CDC) and the National Institute of Environmental Health Sciences (NIEHS) to assess the likely risks to the health of individuals who smoke paraquat drenched marijuana. While the survey of those individuals who reported lung symptoms did not verify that paraquat poisoning had caused chronic or acute lung damage, the report concluded that smoking paraquat laced marijuana has a clear potential for lung damage (Landrigan, Powell, James, & Taylor, 1983). In addition, the assessment revealed that from 1975-1978, the US Government had indirectly funded not only the spraying of paraquat on marijuana farms, but also the spraying of the herbicide 2,4-D on poppy fields, in an attempt to slow down the opium industry.
While the US stopped funding the use of paraquat spraying on marijuana fields in Mexico, in the 1980s, the Reagan Administration funded the spraying of paraquat on marijuana fields in Georgia. Various lawsuits finally ended this practice in the 1990s (Legal Examiner, 2021).
References for this section
- Landrigan,P.J., Powell, K.E., James, L.M., & Taylor, P.R. (1983). Paraquat and marijuana: Epidemiological risk assessment. American Journal of Public Health, 73:784-788.
- Legal Examiner (August 6, 2021). Paraquat history: An in-depth look. The Legal Examiner.
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