Farming and country living (more specifically exposure to pesticides) has often associated with Parkinson’s disease. The findings of numerous epidemiological studies support this connection.
Recently a new study was published that lends considerable support to this idea of factors involved in causing Parkinson’s disease.
In 1986, a group of researchers in the province of Saskatchewan (Canada) made an interesting observation:
Title: Early onset Parkinson’s disease in Saskatchewan–environmental considerations for etiology.
Author: Rajput AH, Uitti RJ, Stern W, Laverty W.
Journal: Can J Neurol Sci. 1986 Nov;13(4):312-6.
PMID: 3779530
They collected the medical details of 21 people who were born & raised Saskatchewan and that later went on to be diagnosed with early onset Parkinson’s disease (that is diagnosis before the age of 40 years). When evaluating the childhood environments of those 21 people, the researchers immediately noticed that 19 of them spent the first 15 years of their lives exclusively in rural Saskatchewan.
This finding has been replicated in different parts of the world. It has also been expanded upon and there is now solid evidence pesticides, but not fungicides, were associated with Parkinson’s disease (click here to read more on this).
So what research has been done recently?
A few weeks ago, some researchers from North Carolina published interesting new results that further supports the association between exposure to pesticides and Parkinson’s disease:
Title: Identification of chemicals that mimic transcriptional changes associated with autism, brain aging and neurodegeneration.
Authors: Pearson BL, Simon JM, McCoy ES, Salazar G, Fragola G, Zylka MJ.
Journal: Nat Commun. 2016 Mar 31;7:11173.
PMID: 27029645 (This report is OPEN ACCESS if you would like to read it)
The researchers grew mouse brain cells in petri dishes, and exposed them to hundreds of chemicals commonly found in the environment and on food. Each petri dish was exposed to just one chemical (for 24 hours), and this was done across many individual petri dishes so that many different chemicals could be tested. They then collected and analysed the RNA of the cells exposed to these chemical, allowing the researchers to access what was happening inside those cells – the molecular reactions to the chemicals. Importantly, they also compared the RNA results between samples – that is to say, they compared the effect that the different chemicals had on the cells by comparing the RNA collected from those cells.
What they found was very interesting.
They identified six basic groupings or clusters of chemicals which share similar mechanistic profiles. This means that the chemicals within each group caused similar RNA activity inside the exposed cells. Of particular interest to us here at the Science of Parkinson’s Disease, is that one of these groups of chemicals (cluster 2) exhibited RNA activity similar to that observed in the aged brain and certain neurodegenerative conditions.
Many of the chemicals in cluster 2 (including fenpyroximate, pyridaben and rotenone), are compounds that target the mitochondria – the power generators inside cells. Rotenone in particular has been associated with Parkinson’s disease (Click here for more on this). It would be interesting to investigate if other chemicals in this clustering have similar effects in models of Parkinson’s disease to that caused by Rotenone.
After identifying these chemicals , the researchers next turned their attention to the chemical usage and food commodity residue database collected by the United States Geological Survey, the United States Department of Agriculture (USDA) and the Food and Drug Administration (FDA). The researchers could use this database to see if what the usage trends were for many of the chemicals in cluster 2. While they found that rotenone usage is low and unchanging, many other chemicals have been used with increasing frequency. This lead the scientists to conclude that there is “significant human exposure potential to many of the chemicals in cluster 2”.
So what does it all mean?
There does appear to be a solid connection between country/rural living and Parkinson’s disease. This association has been replicated across continents and over time. And as we discussed above, we have identified chemicals used in the agricultural industry that can increase the risk of developing the condition.
The fact that the majority of the farming community do not go on to develop Parkinson’s disease, however, brings into question the strength of the association. Obviously there are additional aspects (for example, genetics) that are playing an influence.
Caution should be taken when dealing with many of the chemicals used in the agricultural industry, limiting direct exposure to an absolute minimum. It will be interesting to record if there is any decrease in the prevalence of Parkinson’s disease over time with heightened awareness about the dangers of some of the chemicals used down on the farm.
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