RAYMOND SINGER, PH.D.
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Singer, R. (2002). Neurobehavioral evaluation of residual effects of low-level bystander organophosphate pesticide exposure. Fundamental and Applied Toxicology, Supplement: The Toxicologist, Vol. 55, Number 1, March.
Rationale: Low-level organophosphate pesticide (OP’s) exposure can be neurotoxic. This presentation shows methods and results from an investigation of such an exposure.
Subject: Female, 42 years, high school graduate, farmer, working in a hay field, wearing shorts and a swim suit top, without respiratory protection.
Exposure: Thimet and possibly Lorsban applied to a downwind neighboring field in 6/98, with re-exposure by working in the adjacent field 6-8 times over the next 3 days. On the first evening of exposure, she experienced headache, nausea, vomiting, leg pain, diarrhea, chest tightness, dizziness, blurred vision, and weakness in legs and arms a short while later, symptoms of OP poisoning. She sought emergency care for vertigo, and secondarily nausea, pain etc.. Later and persistent symptoms included memory loss, sleep disorder, fatigue, irritability, and impaired executive function. ACHE testing was inconclusive.
Assessment approach: Comprehensive neurobehavioral toxicity evaluations were performed 2 years post-exposure. The assessment included an extensive interview, administration of tests which have established normative bases and which are known to be sensitive to neurotoxicity, tests for malingering and distortion, and record review (educational, medical, letters of reference).
Findings: Prior IQ was at the 80%tile. The Neurotoxicity Screening Survey showed results consistent with those of patients diagnosed with neurotoxicity. Current Full-scale IQ had declined to the 47th tile, with Processing Speed (a factor very sensitive to global neurotoxicity) at the 8thtile. Additional deficits were seen in detecting visual figure-ground relationships -36th tile; Selective Reminding Test (measures learning) below 1sttile; Stroop Color and Word Test (evaluates mental flexibility ) 31sttile ;Visual Search and Attention Test, (visual detection skills) 23rdtile; logical memory <1sttile; with moderate anxiety and moderate-severe depression.. Distortion was below the level of detection. Malingering was ruled out by 5 separate tests. Personality testing using the NEO Personality Inventory found no personality disorders that could contribute to the findings. Record review found no competing explanations of her illness.
Conclusion: Relatively low-level organophosphate exposure can cause neurotoxicity, revealed by neurobehavioral evaluation, lasting many years after exposure.