Association Between Occupational Toxicity Exposure to Pesticides and Parkinson’s Disease Among Adults: Systematic Review and Meta-Analysis
Authors: Yahya Nur Adriana Aqirah , Meramat Asheila AK 
Published: November 2022

Despite being acknowledged globally as one of the primary environmental pollutants, pesticides appear as one of the toxic compounds that are available purposefully to be used in controlling pests and vectors, especially in agricultural areas [1]. Nevertheless, pesticides have been discovered to be associated with a broad scope of pathologies, especially with Parkinson’s disease (PD) Most previous studies could not determine a significant positive relationship due to the discrepancies in their methodologies. Based on data published by the Department of Statistics Malaysia, the proportion of citizens with PD in Malaysia is anticipated to grow five-fold by 2040, from an estimated 20,000 to 120,000 cases [2].

Hence, this study is employed to deliver an up-to-date systematic review and meta-analysis regarding pesticide exposure and PD which will be based on the highest quality of evidence along with a broader extent of study designs that encompass cohort, case-control and cross-sectional studies to identify the significant link between them. The objective of this study was to find out whether there is an increased risk of PD among adults with occupational exposure to pesticides and to determine the pesticides that are associated with PD.

In formulating the research question, the P (population) E (exposure) C (control) O (outcome) model was used. The search was done from databases such as Google Scholar, Pubmed and Science Direct. The key points used were as followed: “occupational” OR “professional” OR “work-related” OR “job-related” OR/AND “pesticidal” OR “pesticide's” OR “pesticides” OR “pesticide” AND “Parkinson disease” OR “Parkinsons disease” OR “Parkinson's disease” OR “Parkinson” OR “Parkinsons” OR “Parkinson’s”. Meta-analysis was directed by utilizing the Review Manager 5 software to inspect the data regarding work-related pesticide acquaintance and the development of Parkinson’s disease based on all included studies of selected characteristics.

The systematic review encompassed 26 studies where 23 of them displayed a significant association between occupational exposures to pesticides that increased the risk of developing PD. The meta-analysis also supported the hypothesis of this study where work-related pesticide acquaintance showed 89% higher odds to develop PD [OR = 1.89, 95% CI (1.63 to 2.20)]. For specific types of pesticides, organophosphorus contact revealed the strongest association with 89% higher odds [OR = 1.89, 95% CI (1.35 to 2.64)] followed by insecticides contact with 86% higher odds [OR = 1.57, 95% CI (1.58 to 1.92)], organochlorine exposure with 71% higher odds [OR = 1.71, 95% CI (1.21 to 2.41)], fungicides acquaintance at 42% higher odds [OR = 1.42, 95% CI (1.33 to 1.51)] and herbicides contact with 23% higher odds [OR = 1.23, 95% CI (1.03 to 1.46)] to establish PD (Table 1).
Overall, occupational pesticide contact exhibited an increased risk of PD with organophosphorus displaying the strongest association among other specific types of pesticide. The theory concerning the specific kind of pesticides that can lead to PD is inconsistent where it is immensely dependent upon their mechanism of toxicity and chemical composition as well as its explicit biochemical passageways which up until this moment is not yet being fully understood. Hence, the result of this study can supplement advanced knowledge in the literature where it can be utilized to govern further studies and implementations in the future to improve the safety and health of the workers who are involved with pesticides’ application day to day as well as the health of the public. Therefore, a safer class of pesticides may also be invented consequently. On the other hand, it may also aid in future studies to find out the specific biomarkers or reliable tools which can measure the causal relationship between pesticides’ acquaintance and PD more accurately. Thus, the forthcoming studies that can count on more unbiased and quantifiable approaches regarding the evaluation of pesticides’ acquaintance and PD must be fostered.