Effects on the nervous system among welders exposed to aluminium and manganese.

OBJECTIVES: The purpose was to study the effects on the nervous system in welders exposed to aluminium and manganese. METHODS: The investigation included questionnaires on symptoms, psychological methods (simple reaction time, finger tapping speed and endurance, digit span, vocabulary, tracking, symbol digit, cylinders, olfactory threshold, Luria-Nebraska motor scale), neurophysiological methods (electroencephalography, event related auditory evoked potential (P-300), brainstem auditory evoked potential, and diadochokinesometry) and assessments of blood and urine concentrations of metals (aluminium, lead, and manganese). RESULTS: The welders exposed to aluminium (n = 38) reported more symptoms from the central nervous system than the control group (n = 39). They also had a decreased motor function in five tests. The effect was dose related in two of these five tests. The median exposure of aluminium welders was 7065 hours and they had about seven times higher concentrations of aluminium in urine than the controls. The welders exposed to manganese (n = 12) had a decreased motor function in five tests. An increased latency of event related auditory evoked potential was also found in this group. The median manganese exposure was 270 hours. These welders did not have higher concentrations of manganese in blood than the controls. CONCLUSIONS: The neurotoxic effects found in the groups of welders exposed to aluminium and manganese are probably caused by the aluminium and manganese exposure, respectively. These effects indicate a need for improvements in the work environments of these welders.

Facial EMG responses to noise.

Tension of the forehead increases as a response to unpleasant stimuli. In three experiments EMG activity in corrugator muscle was measured to test this response as an indicator of noise annoyance. In Exp. 1 (n = 24) monotonic sound level-response functions were obtained for four levels of 100- and 1000-Hz tones. In Exp. 2 (n = 20) recordings were made during work with a simple and a difficult task in a group of women and a group of men. Larger responses were obtained during the difficult task, especially during noise exposure. The response was much larger for the women. Exp. 3 (n = 24) showed that the sex difference was unaffected by a correction for differences in maximum level of corrugator response. Rated annoyance was a linear function of log EMG.

Human experimental MIBK exposure: effects on heart rate, performance, and symptoms.

Heart rate, performance, and symptoms were studied in six female and six male volunteers, aged 19 to 47 years, during experimental 2-hr exposures to 10 and to 200 mg/m3 of methyl isobutyl ketone (MIBK). No effects from exposure on performance of a reaction time task or an arithmetic test could be demonstrated, and no consistent effects on heart rate were found. Subjects reported significantly more symptoms from the central nervous system, e.g., fatigue, due to the exposure. There was also an indication of an increase in ratings of irritation to the airways. A reduction of the threshold limit value (TLV) of 205 mg/m3 for MIBK exposure presently indicated by the American Conference of Governmental Industrial Hygienists, is therefore recommended.