Epidemiological study (observational study)

Magnetic fields and brain tumour risks in UK electricity supply workers epidem.

By: Sorahan T

Published in: Occup Med 2014; 64 (3): 157-165

Aim of study (acc. to author)

A cohort study was conducted in UK to investigate whether brain tumor risks are related to occupational exposure to low-frequency magnetic fields. The present study is an update of the publication by Sorahan 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

brain tumor: glioma, meningioma

Type of risk estimation:

incidence

(relative risk (RR))

Exposure

- 50/60 Hz
- magnetic field
- occupational

Assessment

calculation: occupational cumulative lifetime exposure calculated for each worker based on the individual job history and the time-weighted average of the magnetic field strength

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): 10.0 - < 20.0 µT
Group 15	occupational exposure to magnetic fields received <10 years ago (lugged exposure): ≥ 20 µT

Population

Group:
- men
- women
Characteristics: employees of the former Central Electricity Generating Board (CEGB) of England and Wales hired in the period 1952-1982 with a minimum of 6 month employment
Observation period: 1973 - 2010
Study location: UK
Data source: National Health Service Central Register

Study size

Type	Value
Total	73,501

Statistical analysis method:

Poisson regression model

(adjustment:

age
sex
socioeconomic status
calender period

)

Results (acc. to author)

For glioma and for the generality of all brain tumors, no increased risks for all exposure categories were observed 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 meningioma, but there was some evidence of elevated risks in the three highest exposure categories for exposures received more than 10 years ago.
The authors concluded that no evidence was found to support the hypothesis that exposure to magnetic fields is a risk factor for gliomas, and the findings are consistent with the hypotheses that both distant and recent magnetic field exposures are not causally related to gliomas. The limited positive findings for meningioma may be chance findings; national comparisons with cancer registry data argue against a causal interpretation.

Study funded by

Energy Networks Association (ENA), UK

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