We evaluated peak exposure to extremely low-frequency magnetic fields (ELF) during the semiconductor manufacturing process based on an analysis of the time exposure patterns of semiconductor workers. This evaluation was manifested by measuring the personal exposure of 117 workers involved in wafer fabrication and chip packaging operations in the semiconductor industry. A portable EMDEX and work diary were used to monitor ELF with high temporal resolution. All ELF measurements (n = 942,885) were recorded every four seconds and categorised by operation and job during work periods exceeding six hours. We defined peak exposure levels as those higher than the arithmetic mean (AM), time-weighted average. The number of peaks per hour, the peak level above the AM and the contribution of peak exposure to the AM were compared by operation and job. ELF exposure ranged from 0.25 uT for chip test operators to 1.76 uT for diffusion maintenance engineers. The average number of peak exposures per hour at semiconductor operations ranged from 302 (die attachment engineers) to 764 (module engineers). The contribution of peak exposure to AM exposure during individual tasks for most workers in fab and chip packaging operations was substantial for higher than 60% of AM, but limited for other jobs, such as wafer test operators (29%) and office workers (50%). The ratio of peak values to average AM ranged from 1.5 (test operators) to 4 (electrical engineers). In conclusion, the level of ELF between peaks was found to be significant in most semiconductor operations, even though they are negligible for jobs with low AM and SD, such as office workers, chemical mechanical plating engineers and die attachment engineers.
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