A method for assessing occupational exposure to power-frequency magnetic fields for electricity generation and transmission workers

Abstract

A new method for assessing both current and historical occupational exposures to magnetic fields has been developed and used in health studies involving a cohort of electricity generation and transmission workers in England and Wales. The exposure values are derived by calculation from engineering and operational data about the power stations rather than from measurements. They are provided for each of 11 job categories for each year of operation of each power station represented in the cohort. The engineering data are used to determine the average magnetic fields in specified areas of work within the power station and then applied to information about the time spent in these areas by each of the job categories. The operational data are used to adjust the exposures for each year according to the power station output for the year. Earlier methods used measurements or the advice of panels of experts to provide exposure scores for a number of job categories across all power stations and years. Such methods were not able to distinguish exposures from different power facilities or during the different years of their operation. Measurement surveys at 10 power stations of the magnetic fields in the work areas gave confidence that the calculations were realistic. Exposure measurements on 215 workers at three power stations were compared in job groups with the exposures predicted by the method. The Pearson correlation coefficient was 0.86 and the slope and intercept of the line of best fit were 0.87 and 0.07 microT respectively. The method gives a good prediction of measured exposure and is being used for studies of occupational exposure to magnetic fields and leukaemia, and of cardiovascular disease, and a reanalysis of brain cancer.

Occupational exposure to magnetic fields relative to mortality from brain tumours: updated and revised findings from a study of United Kingdom electricity generation and transmission workers, 1973–97

“…6 Exposure assessments for the larger power stations were based on the maximum output from each station, annual load factors, typical working patterns, and proximity of departments to the main generator connections. The coded job histories of each study subject were cross referenced with the exposure assessments to obtain individual assessments of exposure to magnetic fields for the period April 1952 to March 1994.…”

Future needs of occupational epidemiology of extremely low frequency electric and magnetic fields: review and recommendations

“…Miller et al constructed a JEM that classifies exposure measurements by location as well as by job 87. Renew et al assessed exposures of power station workers with a magnetic field model that takes account of the engineering design, layout and operational history for each power station 88. Results from this model were combined with the proportion of time spent in specific station areas for each job and with occupational history to give individual exposure values.…”

Cancer incidence in UK electricity generation and transmission workers, 1973–2015

“…An updated analysis of these UK data has been carried out aiming to provide a more complete monitoring of cancer risks in this cohort, and to identify any other types of cancer that merit further investigation. Details of exposure to electric and magnetic fields in this industry have been described before [5,14]. A long list of other occupational exposures present in parts of the industry before 1997 has also been published [15].…”