Analysis of personal and bedroom exposure to ELF-MF in children in Italy and Switzerland

Background: Little is known about the real everyday exposure of children in Europe to extremely low frequency magnetic fields (ELF-MF). This study's aims 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. Methods: In Switzerland and Italy 172 children aged between 5 - 13 years were equipped with ELF-MF measurement devices (EMDEX II, measuring 40-800 Hz) during approx. 48 hours twice, in the warm and the cold season. Additionally 24h measurements were taken in the children's bedroom. Results: 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 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 correlation between bedroom and personal exposure was 0.86 for the geometric mean but considerably lower for the 95th and 99th percentiles (<=0.60). Conclusion: Most previous study 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.