| Objective To monitor the current ELF levels in urban area ofChongqing, in the aim of providing a basis for the relevant departments todevelop scientific and effective protective measures and related healthpolicyMethods Based on the standards set in Guidline on Management ofRadioactive Environmental Protection-Electromagnetic RadiationMonitoring Instruments and Methods (HJ/T10.2-1996), Guidline onManagement of Radioactive Environmental Protection-environmentalImpact assessment methods and standards on electromagnetic radiation(HJ/T10.3-1996), Hygienic Standard for Environmental ElectromagneticWaves (GB9175-88), Regulations for Electromagnetic Radiation Protection(GB8702-88), and Methods of Measurement of Power Frequency EletricField and Magnetic Field from High Voltage Overhead Power TransmissionLine and Substation (DL/T988-2005), we measured:(1) Electric intensityand power density in outside areas adjacent to residential building;(2) ELFintensity of each floor (elevator entrance, stairwell and the roof) withinresidential building;(3) Indoor ELF intensity under three states: state A-people in a standing position with electrical appliance turned off; state B-people in a standing position with electrical appliance turned on; state C-people in a sitting position with electrical appliances turned on;(4) ELF intensity around110kV overhead power transmission line.Results (1) In this study, electric field intensity at the frequency of100kHz~3GHz in outside areas adjacent to the five residential buildings didnot exceed the safety limits of national environmental hygiene standards.Whereas some power density values in region C and E did exceed thelimits.(2) The maximum value of electric field intensity of each floor at thefrequency of1MHz~40GHz among the four residential buildings reached17.18V/m, which was close to the public exposure limit set in Regulationsfor Electromagnetic Radiation Protection (GB8702-88), and the differenceof electric field intensity between each floor was not statistically significant(P>0.05); as for the frequency from5Hz to1kHz, the difference of electricintensity between different residential buildings did not reach statisticalsignificance (P>0.05), whereas that measured on the roof of the buildingnear overhead high-voltage power transmission line was higher than thatmeasured on the roof of other three buildings (P＜0.005), and also higherthan the value of the other floors within the same building (P＜0.005). Themagnetic field intensity of each floor of the residential building near powertransmission line was higher than that of the other three buildings (P＜0.005).(3) Power density at the frequency of100kHz~3GHz did notexceed the limit set in Hygienic standard for environmentalelectromagnetic wave,10V/m. At the frequency of5Hz~1kHz and1kHz~100kHz, when people were in a standing position, electric fieldintensity measured with electric appliances turned on was higher than thatmeasured with electric appliances turned off (P<0.01); as for the frequencyfrom5Hz to1kHz, electric field intensity measured when people were in astanding position was higher than that in a sitting position,with electric appliances turned on in both states (P<0.01); electric field intensity at thefrequency of1MHz~40GHz almost reached the limit set in Guidelines forLimiting Exposure to Time-Varying Electric, Magnetic, andElectromagnetic Fields (up to300GHz) determined by InternationalCommission on Non-Ionizing Radiation Protection (ICNIRP).(4) Themaximum value of electric field and magnetic field intensity at thefrequency of5Hz~1kHz measured at the six monitoring points surround110kV overhead power transmission line was1766.68V/m and0.49μT,respectively, lower than the limits set in ICNIRP guideline,5kV/m and100μT; the electric field intensity on the roof of the building adjacent to theoverhead high-voltage power transmission line ranged between629.50to635.60V/m, which was significantly higher than that of the other floorswithin the same building (P<0.005); electric field intensity measured at thepoints closer to the ground was higher that that measured at theperpendicularly higher points; some values of power density in the streetnearby have exceeded the limits, with the maximum value of22.90μW/cm2.Conclusion (1) In this survey, the environmental ELF intensitymeasured in the outside areas of residential building, within residentialbuilding and the areas around overhead high-voltage power transmissionline did not exceed relevant national standards except a few of them.(2)ELF intensity of different floors is related to the distribution of extremelylow frequency radiation sources. The use of household electric applianceshas made a contribution to the indoor environmental ELF intensity. Thetheoretically positive relation between the total power of electric appliancesand indoor ELF intensity failed to be demonstrated.(3) Overheadhigh-voltage power transmission line, architecture material, construction layout, arrangement of the cable have an effect on environmental ELF level,particularly, overhead high-voltage power transmission line contributedsignificantly to the ELF level in the building nearby.(4) The set-up way ofhigh-voltage line exert an influence on ELF generated by high-voltage line.The electric and magnetic filed intensity generated by overheadhigh-voltage power transmission line decrease with distances increasing.(5)Electromagnetic wave in urban habitat environment are mostlylow-intensity, mixed-frequency wave, in which electromagnetic waves ofextremely low frequency (0Hz~100kHz) plays an important role. |
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