Organophosphorus Insecticides and Mental Alertness

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Abstract
Tests of mental alertness were conducted during 1960, 1961, and 1962 on groups of people with varying degrees of exposure to organic phosphorus pesticides and on controls. In 1960, 2 different pencil and paper tests[long dash]the Gersoni U test and the EX test-were used. On both tests unexposed individuals varied widely in levels of attainment. However, for a given individual the scores attained on the same test at different times were fairly uniform. Only a minor amount of learning occurred. There was little or no difference among the various exposure groups on five of the 6 parameters measured. However, with respect to lines completed on the Gersoni U test, the exposure group as a whole showed a poorer score during the exposure period compared with the nonexposure period while the control group made a better score during the "exposure" period than during the "non-exposure" period. This one difference was the only indication from the 1960 tests that exposure to organic phosphorus insecticides modified mental alertness in clinically well workmen. In 1961 and 1962, a complex reaction time test was used. In this test, also, performance varied widely among different people, but performance for a given individual was relatively constant at different times. Little learning was evident. Both exposed and control groups scored about as well as or better during nonexposure than during exposure periods. The differences were small for both exposed and control groups and were as large, or larger, for the latter as for the former. There was no indication from results of the complex reaction time test that exposure to organic phosphorus insecticides at levels insufficient to produce clinical illness had any important effect on mental alertness. Three of the pilots in the survey crashed during the period of participation. There was no evidence that pesticide exposure was involved as the cause of these incidents. In the clinical study of 187 cases of suspected organic phosphorus poisoning, each case was evaluated on the basis of the relative severity of somatic illness and of mental effect. There were no cases in which mental effect was noted in the complete absence of physical signs or symptoms of illness. Two cases are reported in which an effect on mental alertness was the presenting and/or predominating symptom. The mental alertness tests were given to 11 individuals who had shown symptoms of poisoning by organic phosphorus insecticides recently. In the nine instances in which comparisons were available, the poisoned subjects scored poorer in the acute or early recovery stage of poisoning and then showed progressive improvement during and after convalescence. These test results are consistent with the accepted opinion that organic phosphorus compounds may affect mental alertness if absorbed in amounts great enough to cause clinical signs or symptoms of systemic illness. No cases were seen in which mental effects occurred alone. The constancy of accident rates for cropduster pilots during a time when production and use of organic phosphorus pesticides was increasing rapidly suggests that exposure to these chemicals was not the major cause of aircraft accidents involving cropduster pilots.