Study type: Epidemiological study (observational study)

Epidemiological study of power lines and childhood cancer in the UK: further analyses epidem.

By: Bunch KJ, Swanson J, Vincent TJ, Murphy MF
Published in: J Radiol Prot 2016; 36 (3): 437-455
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Aim of study (acc. to author)

Further analyses from an epidemiological study of childhood cancer and residence at birth near high-voltage power lines in the UK were reported. Previous publications on this study are Draper et al. (2005), Kroll et al. (2010), Bunch et al. (2014), Swanson et al. (2014) and Bunch et al. (2015).

Further details

1.) Three subgroup analyses that were not included in any of the earlier papers are presented: age of child at diagnosis (0, 1-4, 5-9, and 10-14 years), subtype of leukemia and by region of the country (10 different regions).
2.) The aim was to investigate whether the observed declining risk over time from 1962 to 2008 was linked more strongly to year of birth or year of cancer diagnosis or to year of construction of the relevant power line.
3.) Updated magnetic field calculations were performed for the whole study population.

Endpoint/type of risk estimation

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

Exposure

Assessment

Exposure groups

Group Description
Group 1 distance of address at birth to nearest power line: 0 - 199 m
Group 2 distance of address at birth to nearest power line: 200 - 599 m
Group 3 distance of address at birth to nearest power line: 600 - 999 m
Reference group 4 distance of address at birth to nearest power line: ≥ 1000 m
Group 5 calculated magnetic flux density: ≥ 0.4 µT
Group 6 calculated magnetic flux density: 0.2 - 0.39 µT
Group 7 calculated magnetic flux density: 0.1 - 0.19 µT
Reference group 8 calculated magnetic flux density: < 0.1 µT

Population

Case group

Control group

Study size

Cases Controls
Eligible 57,067 -
Evaluable 53,506 66,204

Results (acc. to author)

1.) The results suggest that the elevated risks for childhood leukaemia that were previously found for overhead power lines may be higher for older age at diagnosis and higher for myeloid leukemia rather than lymphoid leukemia. There are differences across regions of birth but not forming any obvious pattern.
2.) The previously reported decline in risk from the 1960s to the 2000s seems to be linked to year of birth or year of cancer diagnosis rather than year of construction of the relevant power line.
3.) A non-significant reduced risk was observed for magnetic flux densities of ≥ 0.4 µT compared to < 0.1 µT (RR 0.50, CI 0.15-1.62) in comparison to earlier analyses (RR 2.00, CI 0.18-22.04). However, calculated magnetic flux densities of ≥ 0.4 µT were observed only for 4 out of 15920 children with leukemia and 10 of 19608 control children.
The authors draw overall conclusions: Some elevated risks for childhood leukaemia associated with overhead power lines were found. These results seem to suggest that there is a factor that can, in some circumstances, lead to raised leukaemia rates in the vicinity of overhead power lines. This effect can be observed to distances of approximately 600 m for 400 kV and 275 kV power lines and to a lesser distance for 132 kV power lines. It has declined progressively from the 1960s and is now not present at all (RR for residential distances < 200 m compared to ≥ 1000 m for all power lines combined, 1960s: 4.50, 2000s: 0.71). This definitely cannot be the effect of magnetic fields alone, and it seems unlikely that magnetic fields are contributing significantly to the excesses at all. The preferred candidate of the authors remains some link between the presence of the power line and socioeconomic or demographic factors in its vicinity.

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