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Is there a link between paraquat and Parkinson’s Disease?

Recently there has been media coverage suggesting a link between the herbicide paraquat and Parkinson’s Disease (PD). Parkinson’s Disease is a degenerative disease of the central nervous system that is more common in the elderly.

According to national support group Parkinson’s Australia (external site), age is, in fact, almost the only definite risk factor currently known with no firm evidence of other environmental or genetic risk factors playing a role.

While this remains the orthodox view, there is a hypothesis that exposure to farm chemicals may be a factor in promoting Parkinson’s Disease in some people.

Support for this hypothesis comes from a variety of different strands of research. Some epidemiological studies suggest an association. Research by the National Institutes of Health (external site) in the United States of America, for example, indicated a statistically significant association between Parkinson’s Disease and the use of two pesticides, rotenone and paraquat. People who used either pesticide appeared likely to develop Parkinson’s Disease approximately 2.5 times more often than non-users. But, underlining the challenges epidemiological studies present, other analyses find no such relationship.

Research using animal models has also suggested a possible link. This research has proposed that laboratory animals exposed to paraquat develop brain changes somewhat similar to Parkinson’s Disease. But this research too has not gone unchallenged, with critics arguing that unrealistic doses of paraquat were often required to promote a response. Other critics have posed the more fundamental question of whether animal studies have any relationship to the exposure people using the chemical might actually receive.

While both epidemiological and laboratory research continues, the findings to date have not provided any clear evidence linking paraquat with Parkinson’s Disease.

Given the status of current research and the tight controls that already exist on the use of paraquat in Australia, there is no current trigger which would justify the APVMA imposing any additional regulatory controls

Paraquat, however, remains under close watch by the APVMA. The chemical is under detailed review by the APVMA and formal advice on the epidemiological and experimental research evidence for the neurotoxicity concerns has been sought from the Office of Chemical Safety and Environmental Health in the Commonwealth Department of Health and Ageing. Information obtained from these processes will be assessed to determine if the science has changed and whether, in turn, the APVMA’s regulatory position on paraquat needs to be strengthened.

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Last updated on 1 October, 2014