Effects of Acceptable Levels of Lead Absorption on Human Performance in Relation to Biochemical and Neurophysiological Changes

Abstract

The ability of workers exposed chronically to lead to perform a number of performance tests has been related to their neurophysiological and biochemical changes. A group of 97 workers exposed to inorganic lead and 109 matched controls were selected from two battery manufacturing plants. The stratification of labour in terms of ability and cleanliness of job was considered to be minimal in these factories; such stratification could lead to apparent drop in performance with increasing blood lead values if less demanding jobs in terms of ability are associated with increased lead exposure. The exposed and control subjects were tested for adding ability, reaction time, grip strength, endurance, tapping speed, eye-hand coordination, tremor ami nerve conduction velocity; blood and urinary lead and amino-levulinic acid in urine were measured. Information on clinical subjective symptoms, smoking and drinking habits was also obtained. Over a blood lead range of 13-79ug/lOOml. no indication of a dose response relationship in exposed and control groups was found for performance tests, motor nerve conduction velocity, lead and aminolevulinic acid in urine. A reduced statistically significant motor nerve conduction velocity has been found for the group of exposed workers in one factory, but not in the other. The changes observed in motor conduction velocity appear to be of no significance in terms of workers' biochemical and performance parameters.