Epidemiological study (observational study)

Nighttime exposure to electromagnetic fields and childhood leukemia: an extended pooled analysis epidem.

By: Schüz J, Svendsen AL, Linet MS, McBride ML, Roman E, Feychting M, Kheifets L, Lightfoot T, Mezei G, Simpson J, Ahlbom A

Published in: Am J Epidemiol 2007; 166 (3): 263-269

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Aim of study (acc. to author)

The risk of childhood leukemia associated with nighttime exposure versus 24-/48- hour exposure to extremely low frequency electromagnetic fields was evaluated. In a previous pooled analysis by Ahlbom et al 2000 the risk was calculated based on 24-/48-hour magnetic field measurements or on historical power-load information. In the present pooled analysis, following studies with data of 24-hour or 48-hour measurements were included: Canada ( McBride et al 1999), Germany (Michaelis et al 1997, Michaelis et al 1998, and Schüz et al, 2001), the United Kingdom ( UK Childhood Cancer Study Investigators 1999), and the USA (Linet et al 1997).

Further details

The hypothesis was tested whether nighttime measurements might represent a more appropriate measure of exposure to extremely low frequency electromagnetic fields than 24-/48-hour measurement. The exposure was assessed either by the geometric mean or by the median during the night time of the measurements.

Endpoint/type of risk estimation

childhood leukemia

Type of risk estimation:

incidence

(odds ratio (OR))

Exposure

Assessment

measurement: 24- or 48-hour measurement in the child's bedroom
calculation: median or geometric mean during the night (10 p.m. to 6 a.m.)

Exposure groups

Group	Description
Reference group 1	nighttime magnetic field exposure: < 0.1 µT
Group 2	nighttime magnetic field exposure: 0.1 - < 0.2 µT
Group 3	nighttime magnetic field exposure: 0.2 - < 0.4 µT
Group 4	nighttime magnetic field exposure: ≥ 0.4 µT

Population

Group:
- children
Age: 0–16 years
Characteristics: childhood leukemia
Observation period: 1988 - 1996
Study location: Canada, Germany, United Kingdom, USA

Study size

Type	Value
Total	1,842

Statistical analysis method:

logistic regression

(adjustment:

age
sex
residential area
socioeconomic status

)

Results (acc. to author)

A statistically significant increased risk for leukemia in children with a nighttime exposure to magnetic fields of 0.4 µT or more was observed. The results of the nighttime exposure analysis differed only marginally from those of the previous pooled analysis.
The results do not support the hypothesis that nighttime measurement is a more appropriate measure of exposure to extremely low frequency electromagnetic fields than 24-/48-hour measurement. The authors concluded that the observed association between extremely low frequency electromagnetic fields and childhood leukemia still lacks an explanation.

Study funded by

Electric Power Research Institute (EPRI), USA

Comments on this article

O'Carroll MJ et al. (2007): Re: "Nighttime exposure to electromagnetic fields and childhood leukemia: an extended pooled analysis"

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