MW: 257.16 g/mol
CAS Number: 1910-42-5
Use and production
Paraquat (N,N'-Dimethyl-4,4'-bipyridinium dichlorid) is today among the most commonly used herbicides.
Paraquat is classified as a non-selective contact herbicide. The key characteristics that distinguish it from other agents used in plant protection products are:
•It kills a wide range of annual grasses and broad-leaved weeds and the tips of established perennial weeds.
•It is very fast-acting.
•It is rain-fast within minutes of application.
•It is partially inactivated upon contact with soil.
Paraquat has been banned in the European Union since 2007.
In the United States, paraquat is available primarily as a solution in various strengths. It is classified as "restricted use", which means that it can be used by licensed applicators only.
There is an ongoing international campaign for a global ban, but the cheap and popular paraquat continues to be unrestricted in most developing countries.
Paraquat is toxic to humans (Category II) by the oral route and moderately toxic (Category III) through the skin. Pure paraquat, when ingested, is highly toxic to mammals, including humans, causing severe inflammation and potentially leading to severe lung damage, acute respiratory distress syndrome (ARDS), and death. The mortality rate is estimated between 60-90%. Paraquat is also toxic when inhaled and is in the Toxicity Category I (the highest of four levels) for acute inhalation effects. For agricultural uses, the EPA determined that particles used in agricultural practices (400–800 μm) are not in the respirable range. Paraquat also causes moderate to severe irritation of the eye and skin.
In 2011, a US National Institutes of Health study showed a link between paraquat use and Parkinson's disease in farm workers.
Accidental deaths and suicides from paraquat ingestion are relatively common. For example, there are more than 5,000 deaths in China from paraquat poisoning every year.