Associate Professor Wesley Thevathasan

Parkinson's is the fastest growing neurological disorder in the world.

By the time patients come to Professor Wesley Thever-Tharsen, a specialist in Parkinson's, many are already dealing with symptoms that have changed their lives.

But in some Australian farming communities, the question isn't just what Parkinson's does, it's why so many seem to be getting it.

For years now, some farmers have been drawing a link to Paraquat, a powerful weed killer.

And while it's already banned in over 60 countries, including the UK and China, it's still used widely on Australian farms.

This month, the chemical regulator is expected to make a final decision on whether it can keep being used here, after a review that's been going since 1997.

Professor Thebertharsen is one of about 50 neurologists who made submissions to that review, calling for it to be banned.

But he says the regulator has ignored them, as well as some of the strongest evidence linking Paraquat to Parkinson's.

I'm Daniel James and you're listening to 7am.

today Professor Wesley Thevitharsen on the farmers who fear Paraquat made them sick and whether Australia's chemical regulator is listening.

It's Friday, June 19th.

Wesley, you said farmers are overrepresented amongst the patients you see.

Tell me about that.

What are you seeing from them?

And you believe that one pesticide in particular, paraquat, could be to blame.

Where does that concern come from?

Even as there's widespread agreement about its toxicity, for years, some of the world's leading scientists have also published studies saying that pesticides like paraquat can also lead to an elevated risk of developing Parkinson's.

Tremors, slowing of movement, difficulty sleeping and stiffness can come later.

Then in more advanced stages, loss of cognitive ability.

So you've noticed the risks, you've had a look into the science behind it, and so you've gone to speak to the communities themselves at forums in rural areas.