Analysis of personal and bedroom exposure to ELF-MFs in children in Italy and Switzerland
Struchen B, Liorni I, Parazzini M, Gängler S, Ravazzani P, Röösli M. nalysis of personal and bedroom exposure to ELF-MFs in children in Italy and Switzerland. J Expo Sci Environ Epidemiol. 2015 Dec 16. doi: 10.1038/jes.2015.80. [Epub ahead of print]
Little is known about the real everyday exposure of children in Europe to extremely low-frequency magnetic fields (ELF-MFs). The aims of this study are to (i) assess personal ELF-MF exposure in children; (ii) to identify factors determining personal and bedroom ELF-MF exposure measurements in children; (iii) to evaluate the reproducibility of exposure summary measures; and (iv) to compare personal with bedroom measurements.
In Switzerland and Italy, 172 children aged between 5 and 13 years were equipped with ELF-MF measurement devices (EMDEX II, measuring 40-800 Hz) during 24-72 h twice, in the warm and the cold season. In addition, 24-h measurements were taken in the bedroom of children.
In our study, sample geometric mean ELF-MF exposure was 0.04 μT for personal and 0.05 μT for bedroom measurements. Living within 100 m of a highest voltage power line increased geometric mean personal exposure by a factor of 3.3, and bedroom measurements by a factor 6.8 compared to a control group. Repeated measurements within the same subject showed high reproducibility for the geometric mean (Spearman's correlation 0.78 for personal and 0.86 for bedroom measurements) but less for the 95th and 99th percentile of the personal measurements (≤0.42). Spearman's correlation between bedroom and personal exposure was 0.86 for the geometric mean but considerably lower for the 95th and 99th percentiles (≤0.60).
Most previous studies on ELF-MF childhood leukaemia used mean bedroom exposure. Our study demonstrates that geometric mean bedroom measurements is well correlated with personal geometric mean exposure, and has high temporal reproducibility.
Extremely low-frequency magnetic fields (ELF-MFs) originate mainly from the use of electricity (Europe 50 Hz, US or Japan 60 Hz), and have been studied as a risk factor for childhood leukaemia since the late 1970s,1 with a current total of more than 30 epidemiological studies. During the last 10 years, several pooled analyses have been published that combined all available data with various exposure indices.2, 3, 4 These pooled analyses consistently found statistically significant increased relative risk estimates for childhood leukaemia for high exposures to ELF-MFs (above 0.3 or 0.4 μT) compared with low exposure (below 0.1 μT). In 2001, the International Agency for Research on Cancer (IARC) examined the body of scientific literature on ELF-MFs and concluded from the subset concerning childhood leukaemia that ELF-MFs should be classified as “possibly carcinogenic to humans” based on “limited evidence of carcinogenicity in humans” and “inadequate evidence of carcinogenicity in experimental animals”.5
This study took place in the framework of the EU FP7 research project ARIMMORA (“Advanced Research on Interaction Mechanisms of electromagnetic exposures with Organisms for Risk Assessments”) ....
Living or attending school within 100 m of a power line with highest voltage (≥220 kV) had the largest impact on the personal ELF-MF broadband exposure. Still, the arithmetic mean exposure of these children was on average moderate with ~0.15 μT, and all but two total exposure values in this group were below 0.4 μT. However, our data indicate that children living further away (100–200 m) or within 50 m of an underground cable are overall not higher exposed to ELF-MFs than other children.
... seasonal changes in electricity consumption is only relevant for highly exposed children whereas in the low-exposure range, the seasonal effect is of minor relevance compared to the random data variability. Children may spend more time indoor than outdoor in the cold season and, this may have also contributed to the seasonal differences of the personal measurements but not the bedroom measurements, which are independent of the behaviour of the children. Other studies17, 30 also found lower temperature or colder seasons to be associated with higher ELF-MF exposure.
Personal and bedroom ELF-MF exposure values in Italy were about 35–45% lower than in Switzerland and lower exposure levels have been found in boys compared to girls. No obvious explanation could be found and, we argue that these findings should not be over interpreted ...
We found mean (arithmetic, geometric or median) bedroom measurements to be strongly (to very strongly) correlated with mean personal exposure measures (Table 5). The correlation we found is somewhat higher than for other studies in adults that reported those correlation coefficients between 0.5 and 0.8,15, 16, 17, 19, 22 which is partly due to our sampling strategy to maximise the exposure range of the sample. In addition, it may reflect the fact that children spend more time at home than adults, in particular the very young children ....
We did not find group differences in the harmonic content of the personal or bedroom measurements, except for the very small sample of participants living in an apartment or home directly adjacent to a transformer that showed an increased but still low average harmonic content (<0 .05="" span=""> μT)....
Our study indicates that personal measurements are very useful to identify factors relevant for exposure in children such as temporal variation in electricity consumption as well as the behaviour of the children. In our study, geometric mean of personal measurements was highly reproducible and very strongly correlated with the geometric mean of bedroom measurements, the exposure metric, which is usually used in epidemiological studies on childhood leukaemia. This demonstrates that geometric mean bedroom exposure (either measured or modelled) is expected to represent long-term ELF-MF exposure of children. Reproducibility and respective correlations were lower for high percentiles or for cumulative exposure time above a threshold indicating that such exposure circumstances are unlikely to be the reason for the observed increased leukaemia risks in epidemiological studies.
Joel M. Moskowitz, Ph.D., Director
Center for Family and Community Health
School of Public Health
University of California, Berkeley
Electromagnetic Radiation Safety
News Releases: http://pressroom.prlog.org/