Because of its high toxicity, the European Union withdrew paraquat from its market in July 2007 [1]

So it's clearly poisonous to humans in high doses, I guess the argument is that perhaps the smaller doses exposed to farmers may not lead to sufficient ingestion to cause harm. The parkinsons seems like pretty clear evidence against that.

> If it simply hasn't been approved in other countries, one can't use that information to infer about its safety.

I don't know why you're trying to defend this with counterfactuals/hypotheticals instead of just googling. Feels like you're bending over backward here.

[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC3657034/