Environmental risk factors and Parkinson's disease in farming communities

Parkinson's Disease

FAMILY and CULTURAL STUDY of PARKINSON'S DISEASE

Brown, Rumsby, Capleton, Rushton and Levy (2006) state that Parkinson's disease (PD) is "...idiopathic disease of the nervous system characterized by progressive tremor, bradykinesia, rigidity, and postural instability." It is reported by Wood-Kaczmar, Gandhi and Wood (2006) that Parkinson's disease (PD) is a neurodegenerative disease that is both common and incurable. The majority of cases are sporadic and of unknown origin but several genes have been identified that, when mutated, give rise to rare, familial forms of the disease. The work of Hancock et al. (2008) states that Parkinson's disease (PD) is characterized by "...progressive depletion of dopaminergic neurons in the substantia nigra that manifests clinically as resting tremor, rigidity, and bradykinesia. Causal genetic variants in multiple genes (parkin, ?-synuclein, DJ-1, PINK1, and LRRK2) have been identified, but altogether, these rare genetic risk factors account for a small fraction of the overall prevalence of PD. The remaining majority of PD cases are likely due to genetic susceptibility variants, environmental influences, and complex gene-environment interactions."

II. Objective

The focus of this present study is to examine a specific population of individuals in regards to prevalence of this group in developing Parkinson's disease. This study has chosen to examine a population that has been exposed to farming chemicals and well water and who have developed this disease.

III. Literature Review

A. Environmental Factors

It was reported by Priyadarshi, Khuder, Schaub and Priyadarshi (2001) in the work entitled: "Environmental Risk Factors and Parkinson's disease: A Metaanlysis" that a study was conducted in order to examine the association between Parkinson's disease (PD) and exposure to environmental factors such as living in a rural area, well water use, farming, exposure to farm animals, or living on a farm, and pesticides. A series of metaanalyses of peer-reviewed studies were performed, using 16 studies for living in rural area, 18 studies for well water drinking, 11 studies for farming, and 14 studies for pesticides."

It is reported that the larger part of the studies reported consistently that risk of PD was elevated upon exposure to rural living and farming environmental factors. However, "Dose-response relationships could not be established due to the imprecise nature of the reported data. Our findings suggest that living in a rural area, drinking well water, farming, and exposure to pesticides may be a risk factor for developing PD." (Priyadarshi, Khuder, Schaub and Priyadarshi, 2001)

In a 2008 report entitled: "Pesticide Exposure and Risk of Parkinson's Disease: A Family-Based Case-Control Study" it is stated that "pesticides and correlated lifestyle factors (e.g. exposure to well-water and farming) are repeatedly reported risk factors for Parkinson's disease (PD) but few family-based studies have examined these relationships." (Hancock, et al., 2008)

In a separate study reported by Fleming, et al. (1994) entitled: 'Parkinson's Disease and Brain Levels of Organoclorine Pesticides" states as follows:

Epidemiological studies have suggested an etiologic relationship between pesticide exposure and Parkinson's disease (PD). Organochlorine pesticides were assayed in postmortem brain samples from 20 PD, 7 Alzheimer's disease (AD), and 14 nonneurological control cases. The three groups were similar in age at death, sex, and demographic variables. Only two of 16 pesticide residues screened were detected." (Fleming, et al., 1994)

However, there was a long-lasting residue of DDT found in the majority of Parkinson's disease cases. Additionally Dieldrin was detected "in 6 of 20 PD brains, 1 of 7 AD, and in none of the 14 control samples. Fleming et al. (1994) states: "Despite the relatively small number of brains assayed, the association between Dieldrin and the diagnosis of PD was highly significant (p = 0.03). Dieldrin, a lipid-soluble, long-lasting mitochondrial poison, should be investigated as a potential etiological agent of Parkinsonism." (Fleming et al., 1994)

V. Recent Study Findings

It was reported on February 27th, 2009 that a team of scientists from Australia and the United States "have used yeast and mammalian cells to discover a connection between genetic and environmental causes of Parkinson's disease." (Psysorg, 2009) the study findings state "So far, we've linked PARK9, alpha-synuclein and manganese toxicity. These linkages are not coincidental. They're likely to be affecting a pathway and we suspect it's a central pathway. To confirm that would be very exciting indeed." (Psysorg, 2009)

Summary and Conclusion

The many genetic and environmental factors that have been identified to be risk factors in developing Parkinson's disease have assisted scientists in understanding the disease more fully however, it appears that the more that comes to light about the risk factors for Parkinson's disease, the more questions that are left unanswered. This disease is attributed to both environmental and genetic risk factors and it is presently unclear precisely what actually causes this disease. Much more in the way of research is needed and most certainly will be applied in this area of study and certainly all of the evidence that has been revealed in previous studies when combined with future upcoming studies will soon serve to better inform science of the precise factors that are either risk or causative in developing Parkinson's disease.