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Title: Cognitive deficits associated with long-term, low-level exposure to organophosphate pesticides : a small group study
Author: Mackenzie Ross, Sarah
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2007
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Organophosphate (OPs) pesticides were derived from World War II nerve gas agents and are being increasingly used around the world for a variety of agricultural, industrial and domestic purposes. Concerns have been expressed about the effects of these chemicals on human health. Chronic ill health may follow recovery from acute organophosphate poisoning, but the possibility that repeated low level exposure may cause ill health is controversial as previous research has yielded inconsistent results. As an occupational group, farmers are considered to be at risk of low level exposure only. Method: The present study compared neuropsychological performance of 25 agricultural workers, exposed to organophosphate pesticides in the course of their work with 22 nonexposed healthy volunteers (controls) who were matched to the exposed group for age, gender, years spent in education and level of intelligence. All of the agricultural workers were involved in litigation. Objective: To establish whether agricultural workers with a history of prolonged exposure to OPs show evidence of cognitive impairment and to determine whether the pattern of cognitive deficit relates to exposure history. Findings: A range of cognitive and emotional problems were identified in agricultural workers. Although general intellectual ability was relatively well preserved in the exposed cohort, they obtained lower scores on tests of auditory verbal memory span, verbal learning, verbal fluency, mental flexibility, reading, visuo-spatial skill and information processing speed, than non-exposed controls. In addition, over 70% of the exposed cohort complained of clinically significant levels of anxiety and depression. They also reported a range of physical symptoms, the most prominent being fatigue, aching muscles and joints, headaches, sleep disturbance and irritability. Exposure history varied enormously amongst individuals who seemed to have similar jobs and many appeared to have a history of undiagnosed acute poisoning. This highlights the importance of taking an adequate exposure history. Conclusions: The question of whether low level exposure to OPs causes ill health will never be resolved without agreed definitions of acute versus low level exposure, adequate assessment of exposure history and consideration of individual vulnerability factors or synergistic effects of chemical combinations that may mediate the doseresponse relationship.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (D.Psy.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available