title: Exposure to static and time-varying magnetic fields from working in the static magnetic stray fields of MRI scanners: a comprehensive survey in the Netherlands.
abstract: Clinical and research staff who work around magnetic resonance imaging (MRI) scanners are exposed to the static magnetic stray fields of these scanners. Although the past decade has seen strong developments in the assessment of occupational exposure to electromagnetic fields from MRI scanners, there is insufficient insight into the exposure variability that characterizes routine MRI work practice. However, this is an essential component of risk assessment and epidemiological studies. This paper describes the results of a measurement survey of shift-based personal exposure to static magnetic fields (SMF) (B) and motion-induced time-varying magnetic fields (dB/dt) among workers at 15 MRI facilities in the Netherlands. With the use of portable magnetic field dosimeters, >400 full-shift and partial shift exposure measurements were collected among various jobs involved in clinical and research MRI. Various full-shift exposure metrics for B and motion-induced dB/dt exposure were calculated from the measurements, including instantaneous peak exposure and time-weighted average (TWA) exposures. We found strong correlations between levels of static (B) and time-varying (dB/dt) exposure (r = 0.88-0.92) and between different metrics (i.e. peak exposure, TWA exposure) to express full-shift exposure (r = 0.69-0.78). On average, participants were exposed to MRI-related SMFs during only 3.7% of their work shift. Average and peak B and dB/dt exposure levels during the work inside the MRI scanner room were highest among technical staff, research staff, and radiographers. Average and peak B exposure levels were lowest among cleaners, while dB/dt levels were lowest among anaesthesiology staff. Although modest exposure variability between workplaces and occupations was observed, variation between individuals of the same occupation was substantial, especially among research staff. This relatively large variability between workers with the same job suggests that exposure classification based solely on job title may not be an optimal grouping strategy for epidemiological purposes.
authors.affiliation: Institute for Risk Assessment Sciences, Division of Environmental Epidemiology, Utrecht University, Utrecht 3508 TD, Netherlands; h.kromhout@uu.nl.
authors.forename: Kristel
authors.initials: K
authors.lastname: Schaap
authors.affiliation: Institute for Risk Assessment Sciences, Division of Environmental Epidemiology, Utrecht University, Utrecht 3508 TD, Netherlands;
authors.forename: Yvette
authors.initials: Y
authors.lastname: Christopher-De Vries
authors.affiliation: The School of Information Technology and Electrical Engineering, University of Queensland, St Lucia, Brisbane, QLD 4072, Australia;
authors.forename: Stuart
authors.initials: S
authors.lastname: Crozier
authors.affiliation: School of Social and Community Medicine, University of Bristol, Bristol BS8 2PS, UK.
authors.forename: Frank
authors.initials: F
authors.lastname: De Vocht
authors.affiliation: Institute for Risk Assessment Sciences, Division of Environmental Epidemiology, Utrecht University, Utrecht 3508 TD, Netherlands; h.kromhout@uu.nl.
authors.forename: Hans
authors.initials: H
authors.lastname: Kromhout
mesh_terms: D000328:Adult; D000368:Aged; D004574:Electromagnetic Fields / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D016273:Occupational Exposure / Q000032:analysis*; D010564:Personnel, Hospital; D013996:Time and Motion Studies; D017132:Workplace; D055815:Young Adult
keywords: EMF; MRI; MRI staff; exposure assessment; exposure variability; occupational exposure; static magnetic fields; time-varying magnetic fields