Investigation on autonomic neurotoxicity of hazardous factors in environmental and occupational health

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To clarify the autonomic neurotoxicites of several hazardous factors in environmental and occupational health, such as lead, toluene, organic solvents including n-hexane, xylene and toluene, stirene, alcohol, vibrating tool operation and video display terminal (VDT) work, the electrocardiographic R-R interval variability (CV_<RR>) was measured in subjects exposed to such factors. Exposures to all the factors, except VDT work, are suggested to cause parasympathetic hypofunction ; in addition, lead and alcohol seem to affect the sympathetic activity. However, no significant effect of VDT work on the autonomic nervous system was found.Based upon an overview of research addressing the effects of environmental and occupational factors on the autonomic nervous system, the following finding were obtained :(1) Excluding the above factors, the effects of trichloroethene, carbon disulphide and mixed pesticides on autonomic nervous function have been investigated. Significant depression of the CV … More _<RR> has been shown in workers exposed to carbon disulphide and mixed pesticides, whereas there were no significant differences in any CV_<RR> parameters between workers with long-term exposure to trichloroethene and healthy controls.(2) Most of the factors appear to have affected the CV_<RR> mainly through depression of parasympathetic activity, suggesting that parasympathetic function is more susceptible to such factors in the environment and workplace than sympathetic function. On the other hand, decreased cardiac vagal tone has been reported to be associated with an increased risk of sudden cardiac death or coronary artery disease ; also, measurements of heart rate variability and the quantification of its spectral components are powerful predictors of cardiovascular morbidity and mortality. Therefore, particular attention should be directed to further discovery of hazardous factors, possibly causing some parasympathetic dysfunction in environmental and occupational health.(3) In the light of these data and previous data regarding the central and peripheral neurotoxicities, the cellular targets of lead in the autonomic nervous system are supposed to be the sympathetic and vagal nerves, and those of organic solvents and vibrating tool operation may be within the brainstem. Less