Safety The etiology of the majority of cases of Parkinson's disease (PD) is unknown. What is known is that the disease is a neurodegenerative disorder that results from a loss of dopaminergic neurons in the area of the brain known as the substantia nigra (Hatfield, 2013). In addition, it is speculated that the disease is related to some type of genetic susceptibility and environmental risk factors that largely remain unidentified. Epidemiological research has suggested that there may be an association between exposure to pesticides and the onset of PD; however, this research is very mixed with some studies indicating that there is such relationship and a number of others failing to demonstrate such an association (Dardiotis, Xiromerisiou, Hadjichristodoulou et al., 2013). Dardiotis et al. (2013) reviewed the research and made a case that perhaps the relationship between pesticide use and PD is moderated by a genetic susceptibility. However, one of the flaws in most of the studies that attempt to link pesticide exposure and PD is that a history of pesticide exposure is often determined by the self-report of the individuals with PD. Individuals who have developed PD may selectively recall being exposed to or using pesticides at sometime in their lives as a result of literature popularizing the view that pesticides may cause PD or may overestimate their exposure due to this perceived cause and effect notion (Dardiotis et al., 2013; Hatfield, 2013; Liew, Wang, Bronstein, & Ritz, 2014). Liew et al. (2014) attempted to avoid the aforementioned issues in the research by using a large population -- based case-control study that employed a Job Exposure Matrix (JEM) to individuals with idiopathic...

Participants with PD were recruited via the use of medical groups (neurologists and other medical personal) and public service announcements; control participants were recruited via a randomized selection method. Stringent exclusion criteria were applied to individuals who were listed as having PD. Nearly 1200 such patients responded to the recruitment procedures; however, only 357 were retained. Controls were selected via two sampling strategies in order to achieve a matched control group (N = 750).
During the data collection phase the trained interviewers were blind to case/control status of the participant and conducted structured telephone interviews to develop the JEM. Job tasks were assigned different likelihoods of pesticide exposure and the results were compared to previous research regarding the weighting procedure in order to ensure that the current data was not being too sensitive regarding pesticide exposure likelihood. Results indicated that there was a 55% increase in the risk of developing PD with high pesticide exposure, 28% increase with a medium exposure, and no association with low exposure. In addition the findings were more telling for men than women; however, this finding is somewhat tainted by the small number of female cases in the highly exposed condition. The results indicated that at least for men direct exposure to pesticides (applying, spraying, and mixing of pesticides) did demonstrate an increased risk for the development of idiopathic PD.

Strengths of the study include the…