Study type: Epidemiological study (observational study)

Magnetic fields and leukaemia risks in UK electricity supply workers. epidem.

Published in: Occup Med (Lond) 2014; 64 (3): 150-156

Aim of study (acc. to author)

A cohort study was conducted in UK to investigate whether leukemia risks are related to occupational exposure to low-frequency magnetic fields. The present study is an update of the publication by Harrington et al (2001).

Further details

The cohort included in the present publication was further analysed for brain tumor risk (Sorahan, 2014) and for neurodegenerative disease risk (Sorahan and Mohammed, 2014). Cumulative occupational lifetime exposure together with exposures received more than 10 years ago (lagged exposures) and those received less than 10 years ago (lugged exposures) were developed for each study participant.
The analyses were performed for the whole cohort and a sub-cohort consisting of 48,768 employees first employed in power stations because the exposure assessments are more detailed for power station workers than for other groups of workers.

Endpoint/type of risk estimation

Type of risk estimation: (relative risk (RR))

Exposure

Assessment

Exposure groups

Group Description
Reference group 1 occupational cumulative lifetime exposure to magnetic field: 0 - < 2.5 µT
Group 2 occupational cumulative lifetime exposure to magnetic field:2.5 - < 5.0 µT
Group 3 occupational cumulative lifetime exposure to magnetic field:5.0 - < 10.0 µT
Group 4 occupational cumulative lifetime exposure to magnetic field: 10.0 - < 20.0 µT
Group 5 occupational cumulative lifetime exposure to magnetic field: ≥ 20 µT
Reference group 6 occupational exposure to magnetic fields received >10 years ago (lagged exposure): 0 - < 2.5 µT
Group 7 occupational exposure to magnetic fields received >10 years ago (lagged exposure): 2.5 - < 5.0 µT
Group 8 occupational exposure to magnetic fields received >10 years ago (lagged exposure): 5.0 - < 10.0 µT
Group 9 occupational exposure to magnetic fields received >10 years ago (lagged exposure): 10.0 - < 20.0 µT
Group 10 occupational exposure to magnetic fields received >10 years ago (lagged exposure): ≥ 20 µT
Reference group 11 occupational exposure to magnetic fields received <10 years ago (lugged exposure): 0 - < 2.5 µT
Group 12 occupational exposure to magnetic fields received <10 years ago (lugged exposure): 2.5 - < 5.0 µT
Group 13 occupational exposure to magnetic fields received <10 years ago (lugged exposure): 5.0 - < 10.0 µT
Group 14 occupational exposure to magnetic fields received <10 years ago (lugged exposure): 5.0 - < 10.0 µT
Group 15 occupational exposure to magnetic fields received <10 years ago (lugged exposure): ≥ 20 µT

Population

Study size

Type Value
Total 73,501
Statistical analysis method: ( adjustment: )

Conclusion (acc. to author)

For all leukemia types, no increased risks were observed in all exposure categories and there was no suggestion of risks increasing with occupational cumulative (or recent or distant) magnetic field exposures. There were no statistically significant dose-response effects shown for acute myeloid leukemia, chronic myeloid leukemia or chronic lymphocytic leukemia. There was a significant positive trend for acute lymphocytic leukemia, but this was mainly based on unusually low risks in the lowest exposure category.
The authors concluded that this study found no convincing evidence to support the hypothesis that exposure to magnetic fields is a risk factor for leukemia, and the findings are consistent with the hypotheses that both distant and recent magnetic field exposures are not causally related to the generality of leukemia. The limited positive findings for acute lymphocytic leukemia may well be chance findings.

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