Health Risk Assessment And Exposure Standard Setup Of Environmental Electromagnetic Fields

With the rapid development of electric power and wireless communication technologies over the last several decades, environmental electromagnetic fields (EMF) become more ubiquitous in the modern society. Public concerns have raised about the possible health effects of exposure to EMF. In EMF research field, the results from studies on environmental EMF exposure induced biological effects are still inconsistent (some are positive, but others are not). It remains unclear that whether exposure to the low intensity of EMF can induce the adverse biological effects and its underlying mechanism. Therefore it has been difficult to perform health risk assessment for EMF exposure and develop exposure restriction limit on environmental EMF. In this study, we have assessed characteristics of population exposure and biological effects of EMF, and then innovatively made a more suitable method for developing exposure standards. In another hand we made a meta-analysis to estimate correlation between exposure to extremely low-frequency electromagnetic fields (ELF-EMFs) and the risk of amyotrophic lateral sclerosis (ALS).PartⅠ. Develop of electromagnetic field exposure standardsTo develop health-based exposure standards of environmental EMF, we have assessed characteristics of population exposure, which were more ubiquitous persistence and inevitability than that of chemical substances. It is possible that the potential cumulative effects of EMF may induce healthy hazards. Health risk assessment assumes that cumulative effects do not occur, so it is unsuitable for us to use health risk assessment alone to develop exposure standard of EMF. In this study, we have paid more attention to the long-term cumulative effects of EMF, to ensure the exposure standards will be more scientific, reasonable and reliable.We made a new method for developing exposure standards. Firstly, select scientific literature through electronic databases according to the including and exclusion criteria; secondly, determine threshold levels from scientific literature; thirdly, select safety factor for threshold levels; fourthly, set exposure limits; lastly, ensure that the exposure limits can be practicable.We set 5μT for exposure limit of power frequency electromagnetic fields, and set 0.04 W/kg (average SAR) for exposure limit of radiofrequency electromagnetic fields.PartⅡ. Occupational exposure to extremely low-frequency electromagnetic fields and amyotrophic lateral sclerosis:A meta-analysisTo estimate relationship between exposure to ELF-EMFs and the risk of ALS by a meta-analysis, we have conductd a meta-analysis, in which sixteen studies were selected from electronic databases including PubMed, Embase, and Cochrane Library. Pooled and separate effect sizes (odds ratio and 95% confidence interval) of the ALS risk from exposure to ELF-EMFs were obtained using the random-effect model. Furthermore, the associations of ELF-EMFs exposure with the ALS risk were estimated based on job title or job-exposure matrix. The heterogeneity across the studies was tested, as was publication bias.In pooled analyses, occupational exposure to ELF-EMFs increased a risk of ALS in pooled studies (RR=1.31,95%CI=1.03-1.66), case-control studies (OR=1.39, 95%CI=1.05-1.84), and cohort studies (RR=1.21,95% CI=0.79-1.86). When the exposure level was defined by job title, similar results were observed. However, no significant associations were found when the exposure level was evaluated by job-exposure matrix. Additionally, significant associations were also found in clinically diagnosed ALS, but not in ALS clarified by death certificate. Moderate heterogeneity occurred in all analyses.Conclusion:This meta-analysis suggests that exposure to ELF-EMFs may increase the risk of ALS among occupational population.