Paraquat Pesticide Allowed to Remain on US Market, with Some Risk Prevention Requirements

On August 2, 2021, the U.S. Environmental Protection Agency (EPA) issued an interim decision indicating that the herbicide paraquat may remain on the market in the United States. This follows the Agency's earlier proposal, during the previous presidential administration, to ban its aerial spraying. In this blog post, we take a look at the herbicide and consider the risk prevention measures recently outlined by the EPA.

About Paraquat

Paraquat is a highly toxic organic viologen compound, and one of the most extensively used herbicides in this country.

IUPAC Name1,1′-Dimethyl[4,4′-bipyridine]-1,1′-diium dichloride
Chemical Formula[(C6H7N)2]Cl2
CAS Registry Number1910-42-5

As a non-selective contact herbicide, paraquat acts on and kills plants quickly. By inhibiting photosynthesis, and via the production of reactive oxygen species, it yields plant cell membrane destruction soon after contact. In addition to its herbicidal properties, paraquat can function as a plant growth regulator, often acting as a desiccant.

Within the United States, paraquat products are classified as Restricted Use Pesticides (RUPs). In addition to the risk of fatality posed by paraquat poisoning, research has shown that exposure to the chemical may increase one's risk of developing Parkinson's disease.

Necessary Risk Prevention Measures

To help prevent and mitigate the potential risks associated with the use of paraquat, the EPA has identified several necessary measures in its recent Interim Registration Review Decision. These include:

  • limiting aerial applications of the chemical to a maximum of 350 acres per applicator per day (this applies to all uses except cotton desiccation)
  • necessitating a residential area drift buffer for all aerial applications of the chemical (75 feet for applications > 0.6 lbs cation/A, 50 feet for applications < 0.6 lbs cation/A
  • prohibiting human flagger use
  • limiting the maximum single application rate for alfalfa to 1.0 lb paraquat cation/A
  • requiring enclosed cabs for applications > 80 acres per day
  • necessitating PF10 respirators or enclosed cabs for applications < 80 acres per day
  • forbidding the use of backpack sprayers or mechanically pressurized handguns
  • requiring a 48-hour Restricted Entry Interval for crop uses (this applies to all uses except cotton desiccation)
  • requiring a 7-day Restricted Entry Interval for cotton desiccation
  • necessitating spray drift management measures

Additional Toxic Chemical Information and More

For accessing additional information on paraquat, as well as a myriad of other chemical substances, ToxPlanet offers invaluable resources.

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