Does 'job predict exposure to magnetic fields?

Koeman et al reported an association between amyotrophic lateral sclerosis and estimated exposure to extremely low-frequency magnetic fields (MF) from a cohort study in the Netherlands.1

The authors omitted to mention the most recent findings from a similarly powered cohort study from the UK electricity supply industry.2 The omission is unfortunate, not just because the UK study found no convincing associations, but also because consideration of the different exposure assessment methods used in these two studies highlights a weakness of the methods used in the Dutch study.

The Dutch study used a job-exposure matrix (JEM) to assess exposure, a modified version of the JEM published by Bowman et al in 2007.3 This latter paper highlighted the problem with assessing exposure to MF using a JEM when it states: ‘The underlying assumption behind all these JEM methodologies is that jobs relate to magnetic field exposure.’...

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