Re paraquat, I recall knowing this potential problem in the mid 1980"s.
Parkinson's disease[edit]
In 2011, a US National Institutes of Health study showed a link between paraquat use and Parkinson's disease in farm workers.[49] A co-author of the paper said that paraquat increases production of certain oxygen derivatives that may harm cellular structures, and that people who used paraquat, or other pesticides with a similar mechanism of action, were more likely to develop Parkinson's.[6] Paraquat-induced toxicity in rats has also been linked to Parkinson's-like neurological degenerative mechanisms.[50] A study by the Buck Institute for Research on Aging showed a connection between exposure to paraquat and iron in infancy and mid-life Parkinson's in laboratory mice.[51] A 2013 meta-analysis published in Neurology found that "exposure to paraquat ... was associated with about a 2-fold increase in risk" of Parkinson's disease.[52]
Paraquat is structurally similar to MPP+, a known fast-acting inducer of Parkinson's disease in primate brains. The chloride of MPP+ was sold under the trade name Cyperquat.
Paraquat also induces oxidative stress in invertebrates such as Drosophila melanogaster. Paraquat-fed flies suffer early-onset mortality and significant increases in superoxide dismutase activity.[53]
While in 2022 UK farmers were calling for a ban on the UK production of paraquat, a BBC article stated that "There is no scientific consensus and many conflicting studies on any possible association between Paraquat and Parkinson's"; in the USA a class action against Syngenta is ongoing; the company refutes the claims but has paid =A3187.5 million into a settlement fund.[54]
