Neuropsychological and Psychiatric Functioning in Sheep Farmers Exposed to Low Levels of Organophosphate Pesticides
The study aim was to determine whether low level exposure to organophosphate pesticides (OPs) causes neuropsychological or psychiatric impairment. Methodological weaknesses of earlier studies were addressed by: recruiting participants who had retired on ill health grounds; excluding participants with a history of acute poisoning, medical or psychiatric conditions that might account for ill health; and exploring factors which may render some individuals more vulnerable to the effects of OPs than others. Performance on tests of cognition and mood of 127 exposed sheep farmers (67 working, 60 retired) was compared with 78 unexposed controls (38 working, 40 retired) and published test norms derived from a cross section of several thousand adults in the general population. Over 40% of the exposed cohort reported clinically significant levels of anxiety and depression compared to less than 23% of controls. Exposed subjects performed significantly worse than controls and standardisation samples on tests of memory, response speed, fine motor control, mental flexibility and strategy making, even after controlling for the effects of mood. The pattern was similar for both working and retired groups. The cognitive deficits identified can not be attributed to mood disorder, malingering, a history of acute exposure or genetic vulnerability in terms of PON1 polymorphisms. Results suggest a relationship may exist between low level exposure to organophosphates and impaired neurobehavioural functioning and these findings have implications for working practice and for other occupational groups exposed to OPs such as Aviation Workers and Gulf War Veterans.
Cognitive function following reported exposure to contaminated air on commercial aircraft: Methodological considerations for future researchers
Cabin air on commercial aircraft is sometimes contaminated with jet engine oils containing organophosphates (OP). Aircrew have complained of chronic ill health and cognitive impairment following exposure to contaminated air, but a debate is ongoing about causation, diagnosis and treatment of long-term effects. The incidence of contaminated air events is difficult to quantify, as commercial aircraft do not have air quality monitoring systems on board. Certain types of aircraft record statistically more fume events than others (e.g. the BAe 146 and Boeing 757) and it has been suggested that airframe may serve as a proxy measure of exposure. The current study sought to investigate this claim, and to determine whether an association exists between exposure to contaminated air and neuropsychological impairment. Twenty-nine pilots were recruited and split into two exposure groups according to aircraft type flown, but few differences were noted between groups in terms of exposure history or cognitive function. Pilots’ profile of cognitive performance deviates from that seen in the normal population, but mirrors that seen in other OP exposed cohorts. In particular they show decrements in performance on tests of attention, psychomotor speed and visual sequencing. Given the safety implications of these findings, future research is warranted.