A study has found farmers' nervous systems might be impacted by exposure to the some of the most widely used pesticides.
In the first study of its kind, the Victorian-based National Centre for Farmer Health tested a group of farmers once a month over 12 months for levels of cholinesterase enzymes, which are needed for the proper functioning of the nervous system.
Toxicologist John Edwards said preliminary research results found those enzymes were lower in farmers with high exposure to organophosphate pesticides.
"When we look at cholinesterase, what we see is the cholinesterase inhibition is also higher in the farmers with higher chemical use," Professor Edwards said.
He said researchers also found that farmers in predominantly cropping regions had higher levels of exposure than other regions.
"We've been able to show that in terms of chemical exposure it does vary throughout the year," he said.
"We have some times of relatively intense exposures and other times of less exposure.
"What we identified was the areas that we expected would have the higher levels of chemical exposures have been shown qualitatively to have the highest level of exposure."
Parkinson's disease risk 'still speculative'
There has long been speculation that exposure to pesticides could lead to Parkinson's disease.
Last year, researchers found a cluster of Parkinson's disease cases in a cropping region of western Victoria where are pesticides were commonly used.
Professor Edwards said the link between Parkinson's disease and pesticides was still speculative.
"The main reason for that is that there has never been a very accurate representation of exposure of people in the farming community, and in other groups as well, to be able to say these factors predispose, or cause, maybe, some diseases, including Parkinson's," he said.
He said the results of the long-term study would help work out whether there was a link.
"Here's a tool now that can give us an accurate measure of exposure," Professor Edwards said.
"Over time this can then be used in studies of disease incidence and prevalence to be able to see, is chemical exposure now one of the predisposing factors?"
Farmer health concerns
Jacquie Cotton, a researcher from the Deakin University school of medicine and the National Centre for Farmer Health, said the pesticide exposure study was launched to address concerns farmers had raised.
"It was something that was often talked about by farmers as a concern, the use of agrochemicals and the effects that they may be having on their body," she said.
Dr Cotton said a previous study had tested farmers' cholinesterase enzyme levels, but this was the first to test over a longer period of time, including during times of higher chemical use on farms.
"We have developed a study that has followed 64 farmers over a 12-month period, testing them for their cholinesterase activity every month," she said.
"We now have a picture across a calendar year of farmers' cholinesterase activity, their chemical exposure and their chemical use."
Cropping farmers most at risk
Farmers involved in the study were drawn from different regions — some were mostly crop farming and others were mixed cropping and animal production.
"There were some potential differences we expected to see about chemical application because of the different enterprises involved in these different areas," Dr Cotton said.
Professor Edwards said the farmers from cropping regions appeared to have the highest levels of chemical exposure, as well as the greatest impact on their cholinesterase levels.
"That might not necessarily be solely the effect of the chemicals, because in terms of risk we need to have a chemical that has a hazardous property, plus exposure in order to get a dose which causes some change," he said.
Data also was gathered on what kind of protective equipment the farmers used to see if they could be worsening their exposure by not following safe practices.
"I think we should also recognise that there are chemicals that are safe to use under the right circumstances, and one of the key issues here is identifying the correct way to use chemicals," Professor Edwards said.
"People here may get a better idea of what are good practices and what are poor practices.
"Then what we can identify is how we can develop better practices over time, so when any chemicals are being used we make sure they are being used safely, for both the farmers and their families."