Study On Occupational Exposure Limits Of Extremely Low Frequency Electromagnetic Fields

Objective:to study the occupational exposure limits of extremely Low frequency electromagnetic fields in China.Methods:At first, the ELF-EMF levels of working environment and personal exposure at different factories which use ELF-EMF widely, such as power factory, grid corporation, resistance welding factory and so on were measured. Then a systematic review(SR) of all papers published from 2000 to 2010 about the health effects of ELF-EMF was done, at the same time some papers which accord with the requirements of meta analysis were selected for meta analysis. And the changes of ECG and blood cells among workers with different exposure levels to ELF-FMF in a grid corporation were analysed. At last, the health effects of ELF-EMF and the occupational exposure situation of ELF-EMF were thought over for discussing the limits of extremely Low frequency electromagnetic Fields in China.Results:At the 500kV and above areas in ultra high pressure substation, More than 90% power electric field intensities of measure points were over 5kV/m. Shielding can decrease the electric field. The magnetic field intensities near reactors and capacitors were often over 100μT, reached near 1mT. The exposure levels of workers in power grid were between 0.04 and 5.0μT.70% were over 0.4μT. The exposure levels of resistance wielding workers often were over 500μT, reached near 1mT.By systematic review, when the electric current reached 10A/m2 in the body, the effects of nerve and muscle might be watched. The chronic exposure to ELF-EMF was related with mammary cancer among the women before menopause. ORMH=1.24, 95%CI=(1.03,1.49). the children leukaemia was also related with exposure to ELF-EMF, ORDL=1.08,95%CI=(0.82,1.42).Took into account gender, age, smoking status, drinking status, genetic history and exposure levels, a logistic regression analysis was conducted to assess the risk between exposure to ELF-EMF and ECG changes. At last the exposutr level was a risk factor, the OR of people with high exposure level was 1.35, P=0.45, compared with control group.10A/m2 was the threshold dose. When the levels of electromagnetic fields were under 10kV/m and 1mT, the safety factor was 3 and 95% environment in China were under the limits. At last, the recommendatory limits of ELF-EMF were following, frequency: 0.001～0.82 kHz, the limit of electric intensity was 500/f V/m, the limit of magnetic flux density was 50/f mT; 0.82～100 kHz, the limit of electric intensity was 610 Vm-1, the limit of magnetic flux density was 3.07×10-2 mT.Conclusion:The areas at ultra high pressure power substation or near reactors and capacitors were the key risk areas of ELF-EMF in power grid. The resistance wielding workers exposured to high intensity of ELF magnetic field. Long-time exposure to ELF-EMF were related with the ECG changes, mammary cancer among the women before menopause and children leukaemia. The ELF-EMF limits which this study recommended were accord with both health and condition of economy and technology of China...