Relationship Between ELF Exposure Level And Health Status Among Chinese In Shanghai

[Background] Electric and magnetic fields exist wherever electricity is generated, transmitted or distributed in power lines or cables, or used in electrical appliances. Since the use of electricity is an integral part of our modern lifestyle, these fields are ubiquitous in our environment. Since the first paper reporting an association between residential extremely low frequency electromagnetic fields (ELF) and childhood leukemia was published in 1979, dozens of increasingly sophisticated epidemiological studies have examined this association, by far the majority of studies have been conducted on power-frequency (50-60Hz) magnetic fields. A number of epidemiological studies have reported a potential association between occupational exposure to ELF and increased incidences of different pathologies including cancer (leukemia, brain cancer and breast cancer), neurodegenerative and cardiovascular diseases, and developmental abnormalities. Additionally, increased indexes of depression, chronic migraines, insomnia, and other ailments have been reported among workers exposed to power-frequency fields. However, in China, information on exposure to ELF is insufficient. Since the health problem caused by ELF is not as obvious as chemicals, the published papers in this area are very limited in China and there were few systematic reports on this topic.[Objective] To understand the exposure levels of residents in Shanghai (general and occupational population)and conduct risk assessment based on the investigation and previous studies.[Methods] A cross-sectional study which could be divided into three sections was conducted in Shanghai local residents.The first part was exposure assessment. Basic information such as demographic characteristics, occupational history of study subjects were collected with questionnaires. Participants were required to wear EMDEX-LITE for typical 24h or 8h to collect the exposure levels of magnetic field.The second part was the investigation on the relations between ELF and health. The exposure level of different occupational population was acquired via HI-3604 ELF meter and EMDEX-LITE. The neurobehavioral function of a sub-group workers were examined with Neurobehavioral Core Test Battery (NCTB) and some neural discomfort symptoms were also conducted. Among the second sub-group, two scales, SAS and CES-D were carried out to obtain information on anxiety and depressive symptoms. Among the third sub-group, workers in a power plant, their data of physical examination were analyzed.The final part was the risk assessment of ELF based on previous literatures and our study.[Results] 363 subjects were investigated in the first part. The compliance of teachers and students was better than occupational population. For all subjects, the median of mean exposure was 0.47μT, with significant difference by age, job, units and districts.105 electricians and 110 controls were recruited in the second part. Magnetic field intensity of 220kV transformer stations was higher than that of 35kV transformer stations. It showed that the exposed worker's emotional state of tension, depression, anger, fatigue and confusion appeared more obvious than those in the control group. The average scores of benton visual retention, correct tapping dots and sum tapping dots of electricians were all lower than those of controls. The prevalence of headache, dizzy, insomnia, dreamful and hypomnesia in electricians were higher than those in the control group.182 subjects were participated in the second chapter of this part. For all subjects, the median of mean exposure was 0.53μT, with significant difference by age and job titles. Besides, the prevalence of anxiety and depression is also different among three occupational groups. While controlled the sex, age and job, we found that when the mean exposure higher than 0.4μT, the incidence of depression was increased sharply and OR was 10.04 (95%CI:2.72-37.13) compared to the group in which mean exposure lower than 0.1μT. In the third chapter, physical examination of 822 power plant workers showed that the top detection rates were cardiovascular and liver diseases.The third part was based on extensive literature review and considered that the acute effect of ELF is unlikely to occur in the daily and working environment because the chance exposure to such high levels is seldom. For long term effects, the consistency of epidemiological evidence suggested the association between ELF and childhood leukemia but the evidence of causation is limited. So, exposure limits based upon epidemiological evidence are not suitable and more studies need to be conducted.