职业暴露和生活接触的低频电磁场与成年人急性髓系白血病——基于病例对照研究的Meta分析

目的 研究职业或居住环境中暴露于电磁场与成年人罹患急性髓系白血病(AML)危险因素的关系.方法 收集发表于1980-2010年共9篇相关病例对照研究,用RevMan5.0软件进行Meta分析.结果 电磁场暴露与AML的OR值为1.24(95%CI:1.11～1.37).以暴露强度＜0.1μT为参照,当暴露值分别为0.1～0.2 μT和≥0.2 μT时,分别为OR=1.17(95%CI:0.98～1.39)和OR=1.5l(95%CI:1.15～1.98).结论 Meta分析显示极低频电磁场可能是成年人AML的危险因素之一.进一步对暴露距离、职业暴露或居住环境暴露进行亚组分析,也均揭示电磁场可增加成年人AML的患病风险.

Abstract：

Objective Studies had suggested that risk of leukemia might be associated with occupational or residential exposures to electromagnetic fields and varied at distance to and level of the exposure or type of occupations. Through pooled analyses, etiologic insight on the associations between exposure and disease might be explained. Methods We carried out a Meta-analysis based on primary data (1980-2010) from 9 studies related to the electric and magnetic fields exposure and acute myeloid leukemia in adults to assess whether the combined results, adjusted for potential confounding, would indicate an association between them. Results In this study the overall estimated OR value was 1.24(95%CI: 1.11-1.37). The odds ratios for exposure categories of 0.1-0.2 μT, ≥0.2 μT, compared with ＜0.1 μT, were 1.17(95%CI: 0.98-1.39) and 1.51 (95%CI: 1.15-1.98),respectively. Conclusion Through employing the alternate cut points, stratification by level of exposure or distance and the relation on different ways of exposure, there appeared consistent evidence of increased risk between acute myeloid leukemia in adults and the extremely low frequency-electromagnetic to field exposure.     

Invited commentary: electromagnetic fields and cancer in railway workers

The ideal study of occupational exposure to electromagnetic fields and cancer risk would have a clear exposure source, historically stable exposures, and comparable groups of exposed and unexposed workers. Cohorts of railway workers have marked exposure contrasts and limited job changes and provide marginally adequate study sizes, but there have been important changes in their exposures over time, and the field frequency involved is unusual. The results of Minder and Pfluger's study (Am J Epidemiol 2001;153:825--35) add modest support for an association between electromagnetic field exposure and leukemia. However, given the large size and high quality of a number of previous studies of occupational electromagnetic field exposure and cancer, additional studies similar to past ones are unlikely to yield important new insights.     

Paternal occupational exposure to electromagnetic fields and neuroblastoma in offspring

Investigators in Texas have reported an association between paternal employment in jobs linked with exposure to electromagnetic fields and risk of neuroblastoma in offspring. In an attempt to replicate this finding, the authors conducted a case-control study in Ohio. A total of 101 incident cases of neuroblastoma were identified through the Columbus (Ohio) Children's Hospital Tumor Registry. All cases were born sometime during the period 1942-1967. From a statewide roster of birth certificates, four controls were selected for each case, with individual matching on the case's year of birth, race, and sex, and the mother's county of residence at the time of the (index) child's birth. Multiple definitions were employed to infer the potential for paternal occupational exposure to electromagnetic fields from the industry/occupation statements on the birth certificates. Case-control comparisons revealed adjusted odds ratios ranging in magnitude from 0.5 to 1.9. For two of the exposure definitions employed--both of which are similar to one used by the Texas investigators--the corresponding odds ratios were modestly elevated (odds ratios = 1.6 and 1.9). Notably, the magnitude of these odds ratios is not inconsistent with the Texas findings, where the exposure definition referred to yielded an odds ratio of 2.1. Because the point estimates in this study are imprecise, and because the biologic plausibility of the association is uncertain, the results reported here must be interpreted cautiously. However, the apparent consistency between two independent studies suggests that future evaluation of the association is warranted.     

Magnetic field exposure and neurodegenerative diseases--recent epidemiological studies

Summary. Objectives To analyse the results of recent studies not yet included in a 2003 report of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) on occupational exposure to low-frequency electromagnetic fields as potential risk factor for neurodegenerative diseases. Methods A literature search was conducted in the online databases of PubMed, ISI Web of Knowledge, DIMDI and COCHRANE, as well as in specialised databases and journals. Eight studies published between January 2000 and July 2005 were included in the review. Results The fi ndings of these studies contribute to the evidence of an association between occupational magnetic field exposure and the risk of dementia. Regarding amyotrophic lateral sclerosis, the recent results confirm earlier observations of an association with electric and electronic work and welding. Its relationship with magnetic field exposure remains unsolved. There are only few findings pointing towards an association between magnetic field exposure and Parkinson’s disease. Conclusions The epidemiological evidence for an association between occupational exposure to low-frequency electromagnetic fields and the risk of dementia has increased during the last five years. The impact of potential confounders should be evaluated in further studies. Submitted: 4 August 2005; Accepted: 6 March 2006     

Leukemia in electric utility workers: the evaluation of alternative indices of exposure to 60 Hz electric and magnetic fields

BACKGROUND: Epidemiological studies have inconsistently demonstrated a positive relationship between magnetic and/or electric fields and leukemia. Although exposure to both 60 Hz electric and magnetic fields can be characterized in many ways, to date, risk assessment has been performed by using only a limited number of exposure indices. METHODS: The associations between adult leukemia and indices of electric and magnetic fields were explored within a nested case-control study of 31,453 Ontario electric utility workers. RESULTS: The percentage of time spent above electric field thresholds of 20 and 39 V/m was predictive of leukemia risk after adjusting for duration of employment and the arithmetic mean exposure to both electric and magnetic fields (P<0.05). Duration of employment was strongly associated with an increased risk of leukemia. Those who had worked for at least 20 years, and were in the highest tertiles of percentage of time spent above 10 and 20 V/m had odds ratios of 10.17 (95% CI = 1.58-65.30) and 8.23 (95% CI = 1. 24-54.43), respectively, when compared to those in the lowest tertile. Nonsignificant elevations in risk were observed between indices of magnetic fields and leukemia. CONCLUSIONS: Our results support the hypothesis that electric fields act as a promoting agent in the etiology of adult leukemia. Exposure assessment based on alternate indices of electric and magnetic fields should be incorporated into future occupational studies of cancer.     

Nighttime exposure to electromagnetic fields and childhood leukemia: an extended pooled analysis

It has been hypothesized that nighttime bedroom measurements of extremely low frequency electromagnetic fields (ELF EMF) may represent a more accurate reflection of exposure and have greater biologic relevance than previously used 24-/48-hour measurements. Accordingly, the authors extended a pooled analysis of case-control studies on ELF EMF exposure and risk of childhood leukemia to examine nighttime residential exposures. Data from four countries (Canada, Germany, the United Kingdom, and the United States) were included in the analysis, comprising 1,842 children diagnosed with leukemia and 3,099 controls (diagnosis dates ranged from 1988 to 1996). The odds ratios for nighttime ELF EMF exposure for categories of 0.1-<0.2 microT, 0.2-<0.4 microT, and >or=0.4 microT as compared with <0.1 microT were 1.11 (95% confidence interval (CI): 0.91, 1.36), 1.37 (95% CI: 0.99, 1.90), and 1.93 (95% CI: 1.11, 3.35), respectively. The fact that these estimates were similar to those derived using 24-/48-hour geometric mean values (odds ratios of 1.09, 1.20, and 1.98, respectively) indicates that the nighttime component cannot, on its own, account for the pattern observed. These results do not support the hypotheses that nighttime measures are more appropriate; hence, the observed association between ELF EMF and childhood leukemia still lacks a plausible explanation.     

Adult and childhood leukemia near a high-power radio station in Rome,Italy

Some recent epidemiologic studies suggest an association between lymphatic and hematopoietic cancers and residential exposure to high-frequency electromagnetic fields (100 kHz to 300 GHz) generated by radio and television transmitters. Vatican Radio is a very powerful station located in a northern suburb of Rome, Italy. In the 10-km area around the station, with 49,656 residents (in 1991), leukemia mortality among adults (aged >14 years; 40 cases) in 1987-1998 and childhood leukemia incidence (eight cases) in 1987-1999 were evaluated. The risk of childhood leukemia was higher than expected for the distance up to 6 km from the radio station (standardized incidence rate = 2.2, 95% confidence interval: 1.0, 4.1), and there was a significant decline in risk with increasing distance both for male mortality (p = 0.03) and for childhood leukemia (p = 0.036). The study has limitations because of the small number of cases and the lack of exposure data. Although the study adds evidence of an excess of leukemia in a population living near high-power radio transmitters, no causal implication can be drawn. There is still insufficient scientific knowledge, and new epidemiologic studies are needed to clarify a possible leukemogenic effect of residential exposure to radio frequency radiation.     

极低频电磁场暴露的健康效应

旨在使人们对环境极低电磁场暴露的健康效应有一个正确的认识，从流行病学研究和整体动物研究两个方面，对极低频电磁场暴露的健康危害进行了评价，提示环境极低频电磁场暴露与肿瘤的危险度，以及其他非肿瘤性健康效应之间的相关性是很微弱的，甚至是不确定的。     

Effects of the analytical treatment of exposure data on associations of cancer and occupational magnetic field exposure

Epidemiological studies of cancer among workers exposed to magnetic fields have yielded inconsistent results. This variability may be partly explained by differences in study methods. To assess sensitivity to such methods, data from a previous study of brain cancer and leukemia among electric power company workers were reanalyzed using alternative models, which incorporated uncertainty about the intensity of historical exposures, alternative cut points for categorizing the exposure variable for analysis, and a range of lags for describing cancer latency. Mortality rate ratios for leukemia ranged from 0.8–1.5. For brain cancer, increasing cumulative magnetic field exposure was associated with increasing mortality in virtually all models, with rate ratios between 1.3–3.4 for the most exposed workers. These rate ratios are consistent with previous analyses suggesting a 1.5–3.0-fold increase in the risk of brain cancer but no association with leukemia, and confirm that the previous results are not dependent on arbitrary decisions in applying the exposure data. Am. J. Ind. Med. 34:49–56, 1998. © 1998 Wiley-Liss, Inc.     

A case cohort study of suicide in relation to exposure to electric and magnetic fields among electrical utility workers.

OBJECTIVES--This case cohort study examines whether there is an association between exposure to electric and magnetic fields and suicide in a population of 21,744 male electrical utility workers from the Canadian Province of Québec. METHODS--49 deaths from suicide were identified between 1970 and 1988 and a subcohort was selected comprising a 1% random sample from this cohort as a basis for risk estimation. Cumulative and current exposures to electric fields, magnetic fields, and pulsed electromagnetic fields (as recorded by the POSITRON meter) were estimated for the subcohort and cases through a job exposure matrix. Two versions of each of these six indices were calculated, one based on the arithmetic mean (AM), and one on the geometric mean (GM) of field strengths. RESULTS--For cumulative exposure, rate ratios (RR) for all three fields showed mostly small non-significant increases in the medium and high exposure groups. The most increased risk was found in the medium exposure group for the GM of the electric field (RR = 2.76, 95% CI 1.15-6.62). The results did not differ after adjustment for socioeconomic state, alcohol use, marital state, and mental disorders. There was a little evidence for an association of risk with exposure immediately before the suicide. CONCLUSION--Some evidence for an association between suicide and cumulative exposure to the GM of the electric fields was found. This specific index was not initially identified as the most relevant index, but rather emerged afterwards as showing the most positive association with suicide among the 10 indices studied. Thus the evidence from this study for a causal association between exposure to electric fields and suicide is weak. Small sample size (deaths from suicide) and inability to control for all potential confounding factors were the main limitations of this study.     

A mortality study of electrical utility workers in Québec.

OBJECTIVES--The objective of this study was to investigate the mortality of electrical utility workers exposed to electric and magnetic fields. METHODS--A historical cohort mortality study was carried out on 21,744 workers who were employed in an electrical company in the province of Québec between 1970 and 1988. The last job held by each study subject was coded. A job exposure matrix (JEM) was used to estimate the exposure to 60 Hz electric and magnetic fields, and pulsed electromagnetic fields (as recorded by the PEMF (POSITRON) meter) in this job. Standardised mortality ratios (SMRs) were calculated relative to Québec men. Because the exposure was exclusively among blue collar workers, the remainder of the analyses by exposure were restricted to them. Rate ratios (RRs) in the exposed groups relative to the background groups were estimated with Poisson regression. There were 1582 deaths by the end of follow up. RESULTS--SMRs were almost all below one and never substantially increased, although there were a few increased rate ratios (RRs). There was a significant RR of 2.00 (95% confidence interval (95% CI) 1.37-2.93) for deaths caused by accidents and violence in workers exposed to magnetic fields, RR of 1.82 (95% CI 1.25-2.65) for electric fields, and RR of 1.62 (95% CI 1.13-2.32) for pulsed electromagnetic fields. Occupational accidents related to power lines explain some of the excess of deaths from accidents and violence. Some association was found between magnetic fields and leukaemia, brain cancer, and suicide, between electric fields and brain cancer and suicide, and between pulsed electromagnetic fields and lung cancer, but these were not significant. CONCLUSION--These results are broadly reassuring that major causes of death are not strongly associated with exposure to electric and magnetic fields, but small numbers and approximate exposure assessments preclude the denial of any risk, in particular if it were to affect a rare cause of death.     

A review of epidemiological studies of the health effects of living near or working with electricity generation and transmission equipment

In the last ten years there has been increasing concern that the extremely low frequency (ELF), non-ionising electromagnetic fields emitted by electrical installations and equipment using alternating current at 50-60 Hertz might have long-term effects on health. Studies of the association between disease and residence near installations transmitting or generating electricity and studies of the health of workers in the electrical industry are reviewed. Most of the investigations relate to cancer, although other conditions such as outcome of pregnancy have been studied. The most consistent finding is that electrical workers appear to be at increased risk of leukaemia, especially acute myeloid leukaemia. The effect is small. Combining the results of eleven separate investigations suggests an 18% increase in the risk of leukaemia (RR = 1.18, 95% confidence interval (CI) 1.09-1.29) which is partly or wholly due to a 46% increase in the risk of acute myeloid leukaemia (RR = 1.46, 95% CI 1.27-1.65). It is not clear whether this increase is specific to certain types of work within the electrical industry. Nor is it possible to determine from the available data if the increase in leukaemia is due to electromagnetic fields or to other factors to which electrical workers are exposed. There is no clear association between cancer risk and residence near sources transmitting electricity, although some data suggest that there may be small increases in leukaemia in those living very close to the sources. The relationship between adverse outcome of pregnancy and exposure to sources of ELF electromagnetic fields needs further investigation. Studies of the possible effects of ELF electromagnetic fields on health are hampered by problems in measuring exposure and by the ubiquity of exposure in the community.     

Radon exposure and the risk of leukemia: a review of epidemiological studies

Since the 1990's, several authors estimated that radon inhalation may deliver a small amount of irradiation to the red bone marrow, and consequently may increase the risk of leukemia in humans. The objective of this review is to conduct a critical analysis of epidemiologic results currently available concerning the relationship between radon exposure and the risk of leukemia. Nineteen ecological studies, six miner cohort studies, and eight case-control studies published between 1987 and 2000 are included in this review. The limitations associated with each of these studies are discussed. The results of the ecological studies are relatively concordant and suggest an association between radon concentrations and the risk of leukemia at a geographic level. But these ecological studies present important limitations, and some are only crude analyses. Moreover, the results of the cohort and case-control studies, based on individual data, do not show any significant association between radon exposure and leukemia risk. Our conclusion is that the overall epidemiologic results currently available do not provide evidence for an association between radon exposure and leukemia.     

Is epidemiology implicating extremely low frequency electric and magnetic fields in childhood leukemia?

We have reviewed epidemiological studies examining the association between residential exposure to extremely low frequency electric and magnetic fields (ELF-EMF) and childhood leukemia. We have excluded studies focusing on electrical appliances, because it is difficult to consolidate transient exposure from multiple sources and equally difficult to control information bias. We have identified 24 studies of residential exposure to ELF-EMF and childhood leukemia. About half of these studies were reported as positive and the remaining as null. For each of the studies reported as positive, however, one or more sources of bias could not be confidently excluded. Moreover, studies which were methodologically more sound, or benefited from high quality registry data, were more frequently null than other investigations. We conclude that the empirical evidence in support of an association between ELF-EMF and childhood leukemia is weak.     

An exploratory investigation of suicide and occupational exposure

This exploratory study evaluated the association between suicide and occupational exposure to electromagnetic fields, pesticides, and hydrocarbon solvents. The study population comprised 11,707 suicide deaths and 132,771 eligible controls identified from United States death certificate files for the years 1991 and 1992. Exposure assignment was based on job title reported on the death certificates. Exposure to electromagnetic fields and pesticides was weakly associated with suicide risk, while little evidence for an increased risk was seen for hydrocarbon solvents. The association for electromagnetic field exposure was highest for suicide between the ages 20 and 35 (odds ratio; OR = 1.5), while the highest risk of suicide for pesticide exposure was seen between the ages of 35 and 49 years (OR = 1.5). Further investigation to replicate these findings seems warranted, using higher quality occupational data.     

The possible role of radiofrequency radiation in the development of uveal melanoma

There are few epidemiologic studies dealing with electromagnetic radiation and uveal melanoma. The majority of these studies are exploratory and are based on job and industry titles only. We conducted a hospital-based and population-based case-control study of uveal melanoma and occupational exposures to different sources of electromagnetic radiation, including radiofrequency radiation. We then pooled these results. We interviewed a total of 118 female and male cases with uveal melanoma and 475 controls matching on sex, age, and study regions. Exposure to radiofrequency-transmitting devices was rated as (a) no radiofrequency radiation exposure, (b) possible exposure to mobile phones, or (c) probable/certain exposure to mobile phones. Exposures were rated independently by two of the authors who did not know case or control status. We used conditional logistic regression to calculate odds ratios (ORs) and 95% confidence intervals (95% CIs). We found an elevated risk for exposure to radiofrequency-transmitting devices (exposure to radio sets, OR = 3.0, 95% CI = 1.4-6.3; probable/certain exposure to mobile phones, OR = 4.2, 95% CI = 1.2-14.5). Other sources of electromagnetic radiation such as high-voltage lines, electrical machines, complex electrical environments, visual display terminals, or radar units were not associated with uveal melanoma. This is the first study describing an association between radiofrequency radiation exposure and uveal melanoma. Several methodologic limitations prevent our results from providing clear evidence on the hypothesized association.     

Exposure to residential electric and magnetic fields and risk of childhood leukemia.

The relation between exposure to electric and magnetic fields in the home, as assessed by measurements, wiring configuration, and self-reported appliance use, and risk of leukemia was investigated in a case-control study among children from birth to age 10 years in Los Angeles County, California. Cases were ascertained through a population-based tumor registry from 1980 to 1987. Controls were drawn from friends and by random digit dialing. Interviews were obtained from 232 cases and 232 controls. Available for analysis were measurements of the magnetic field in the child's bedroom over 24 hours or longer (164 cases and 144 controls), spot measurements of magnetic and electric fields (140 cases and 109 controls), and wiring configuration (219 cases and 207 controls). No clear associations between leukemia risk and measured magnetic or electric fields were seen. An association between the Denver Wertheimer-Leeper wiring configuration and childhood leukemia risk was observed (odds ratio for very high relative to very low current and underground configuration combined = 2.15, 95% confidence interval 1.08-4.28; p for trend = 0.008) and was not substantially altered by adjustment for potential confounding factors. Cases were more likely than controls to report use of several appliances that produce high electric and magnetic fields. Our results support an association between childhood leukemia risk and wiring configuration, but not direct measurements of electric and magnetic fields.     

Occupational electromagnetic fields and leukemia and brain cancer: an update to two meta-analyses

OBJECTIVE:: To update past meta-analyses on occupational electromagnetic fields (EMF) and adult brain cancer and leukemia. METHODS:: We collected and evaluated all relevant 1993 to 2007 publications. Summary estimates were obtained using various weighting schemes. To explore sources of heterogeneity, study characteristics were examined using regression analysis. RESULTS:: Overall, for new studies, both brain cancer and leukemia showed small increases in risk estimates, 10% and 13%, respectively. Notably, pooled risk estimates were lower than in past meta-analyses, and leukemia subtypes showed no consistent pattern when past and present meta-analyses were compared. CONCLUSIONS:: The lack of a clear pattern of EMF exposure and outcome risk does not support a hypothesis that these exposures are responsible for the observed excess risk. Findings were not sensitive to assumptions, influential studies, weighting schemes, publication bias, study characteristics, or funding source.     

Implications from epidemiologic studies on magnetic fields and the risk of childhood leukemia on protection guidelines

The objective of this review is to discuss the impact of findings in epidemiological studies on magnetic fields and the risk of childhood leukemia on the definition of exposure limits. A large number of epidemiological studies have consistently shown an association between the risk of childhood leukemia and residential extremely low-frequency magnetic field exposures. There is virtually no supportive data from experimental research and, so far, no proposed explanation has reached a level beyond speculation. The contradictory results from epidemiological and experimental research may either be due to methodological limitations creating a spurious association in the epidemiological studies or to a failure of experimental research to examine mechanisms relevant in the complex origin of childhood leukemia. Taking this together, the overall evidence is not strong enough to demand a revision of the current guidelines for public protection. Application of precautionary measures may be an option; however, decision-makers should be advised that these measures are often not straightforward and a careful evaluation of a possible benefit needs to be performed for each individual situation. Undoubtedly there are gaps in research, and no substantial contribution for clarification of the apparent inconsistencies emerges from recent studies. However, there are important lessons to learn, either with respect to the etiology of childhood leukemia or with respect to the need for improving epidemiological methods for the identification of presumably weak associations.     

Chlorinated hydrocarbon solvents: Substituting our way toward human carcinogenicity

A discussion of the history of substitutions in industrial solvent use is presented, and animal carcinogenicity studies with certain chlorinated hydrocarbon solvents are reviewed. The present knowledge on the association between occupational exposure to chlorinated hydrocarbon solvents and human carcinogenicity is summarized, including a critical review of 23 studies pertaining to human carcinogenicity. Several deficiencies are identified in these studies that make interpretation of the results uncertain, including poor characterization of exposures in qualitative and quantitative terms, the small numbers of deaths or cases, and short follow-up periods. Despite these weaknesses, we conclude that, when viewed collectively, the evidence strongly suggests that occupational exposures to chlorinated hydrocarbon solvents are associated with an excess human cancer risk. The literature supports an association between occupational exposures to chlorinated hydrocarbons and elevated risks of leukemia, lymphoma, and urinary tract cancer. Parental occupational exposures are consistently associated with an elevated childhood cancer risk in the offspring. © 1993 Wiley-Liss, Inc.