Abstract：
The association between childhood leukemia and extremely low frequency magnetic fields (ELF-MF) generated by power lines and various electric appliances has been studied extensively during the past 40 years. However, the conditions under which ELF-MF represent a risk factor for leukemia are still unclear. Therefore, we have performed a systematic review and meta-analysis to clarify the relation between ELF-MF from several sources and childhood leukemia. We have systematically searched Medline, Scopus, Cochrane Database of Systematic Review and DARE to identify each article that has examined the relationship between ELF-MF and childhood leukemia. We have performed a global meta-analysis that takes into account the different measures used to assess magnetic field exposure: magnetic flux density measurements (<0.2 µT vs. >0.2 µT), distances between the child\'s home and power lines (>200 m vs. <200 m) and wire codings (low current configuration vs. high current configuration). Moreover, meta-analyses either based on magnetic flux densities, on proximity to power lines or on wire codings have been performed. The association between electric appliances and childhood leukemia has also been examined. Of the 863 references identified, 38 studies have been included in our systematic review. Our global meta-analysis indicated an association between childhood leukemia and ELF-MF (21 studies, pooled OR=1.26; 95% CI 1.06-1.49), an association mainly explained by the studies conducted before 2000 (earlier studies: pooled OR=1.51; 95% CI 1.26-1.80 vs. later studies: pooled OR=1.04; 95% CI 0.84-1.29). Our meta-analyses based only on magnetic field measurements indicated that the magnetic flux density threshold associated with childhood leukemia is higher than 0.4 µT (12 studies, >0.4 µT: pooled OR=1.37; 95% CI 1.05-1.80; acute lymphoblastic leukemia alone: seven studies, >0.4 µT: pooled OR=1.88; 95% CI 1.31-2.70). Lower magnetic fields were not associated with leukemia (12 studies, 0.1-0.2 µT: pooled OR=1.04; 95% CI 0.88-1.24; 0.2-0.4 µT: pooled OR=1.07; 95% CI 0.87-1.30). Our meta-analyses based only on distances (five studies) showed that the pooled ORs for living within 50 m and 200 m of power lines were 1.11 (95% CI 0.81-1.52) and 0.98 (95% CI 0.85-1.12), respectively. The pooled OR for living within 50 m of power lines and acute lymphoblastic leukemia analyzed separately was 1.44 (95% CI 0.72-2.88). Our meta-analyses based only on wire codings (five studies) indicated that the pooled OR for the very high current configuration (VHCC) was 1.23 (95% CI 0.72-2.10). Finally, the risk of childhood leukemia was increased after exposure to electric blankets (four studies, pooled OR=2.75; 95% CI 1.71-4.42) and, to a lesser extent, electric clocks (four studies, pooled OR=1.27; 95% CI 1.01-1.60). Our results suggest that ELF-MF higher than 0.4 µT can increase the risk of developing leukemia in children, probably acute lymphoblastic leukemia. Prolonged exposure to electric appliances that generate magnetic fields higher than 0.4 µT like electric blankets is associated with a greater risk of childhood leukemia.
摘要：
在过去的40年中，已经广泛研究了儿童白血病与电力线和各种电器产生的极低频磁场（ELF-MF）之间的关联。然而,目前尚不清楚ELF-MF是白血病的危险因素.因此,我们进行了系统评价和荟萃分析,以阐明来自多个来源的ELF-MF与儿童白血病之间的关系.我们系统地搜索了Medline,Scopus,Cochrane系统评价数据库和DARE，以确定研究ELF-MF与儿童白血病之间关系的每篇文章。我们进行了一项全球荟萃分析，考虑了用于评估磁场暴露的不同措施：磁通量密度测量(<0.2µTvs.>0.2µT),儿童家庭和电源线之间的距离(>200米与<200m)和导线编码(低电流配置与高电流配置)。此外，基于磁通量密度的荟萃分析，在接近电力线或电线编码已经执行。还检查了电器与儿童白血病之间的关联。在确定的863个参考文献中，38项研究已纳入我们的系统评价。我们的全球荟萃分析表明儿童白血病与ELF-MF之间存在关联(21项研究，合并OR=1.26；95%CI1.06-1.49)，这种关联主要由2000年之前进行的研究解释(早期研究：合并OR=1.51；95%CI1.26-1.80vs.后期研究：合并OR=1.04；95%CI0.84-1.29）。我们仅基于磁场测量的荟萃分析表明，与儿童白血病相关的磁通量密度阈值高于0.4µT（12项研究，>0.4µT：合并OR=1.37；95%CI1.05-1.80；仅急性淋巴细胞白血病：七项研究，>0.4µT：合并OR=1.88；95%CI1.31-2.70）。较低的磁场与白血病无关（12项研究，0.1-0.2µT：合并OR=1.04；95％CI0.88-1.24；0.2-0.4µT：合并OR=1.07；95％CI0.87-1.30）。我们仅基于距离的荟萃分析（五项研究）表明，居住在50m和200m电力线内的合并OR分别为1.11（95％CI0.81-1.52）和0.98（95％CI0.85-1.12），分别。分别分析的50m电力线和急性淋巴细胞白血病的合并OR为1.44（95％CI0.72-2.88）。我们的荟萃分析仅基于导线编码（五项研究）表明，非常高电流配置（VHCC）的合并OR为1.23（95％CI0.72-2.10）。最后,暴露于电热毯后，儿童白血病的风险增加(四项研究，合并OR=2.75；95%CI1.71-4.42)和，在较小程度上，电钟(四项研究，合并OR=1.27；95%CI1.01-1.60)。我们的结果表明，ELF-MF高于0.4µT可以增加儿童患白血病的风险，可能是急性淋巴细胞白血病.长时间接触产生高于0.4µT的磁场的电器，如电热毯，与儿童白血病的风险更大。
