RAYMOND SINGER,
PH.D.
A Professional
Association
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36
Alondra Road / Santa Fe, New Mexico / 87505
Alternate office: 180 E.
79th Street / Suite 1-C / New York, N.Y. / 10021
Telephone: (505)
466-1100 / Fax: (505) 466-1101 / E-mail: ray.singer@gmail.com
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.