Occupational exposure to magnetic fields and brain tumours in Central Sweden

Occupations with exposure to magnetic fields were studied in a population-based case-control study of male glioma and meningioma in Central Sweden. The study included 84 cases of glioma, 20 cases of meningioma and 155 controls. Information about job titles was obtained by means of a questionnaire. Three different methods were used to classify exposure 1) 'electrical occupations', 2) assessment of magnetic fields by an electrical engineer, 3) job values based on magnetic field measurements at work sites for occupational groups. When analyses were based on 'electrical occupations' a relative risk (RR) of 1.0 (95% CI: 0.4–2.4) was seen for glioma and 1.8 (95% CI: 0.3–3.6) for meningioma. When analyses were based on measurements a relative risk of 1.9 (95% CI: 0.8–5.0) was seen for glioma and 1.6 (95% CI: 0.3–10.2) for those ever in an exposed job of an average mean value of > 0.4T. A larger number of individuals was classified as exposed, when exposure was based on measurements. Information was available regarding several potential confounders, but none of them seemed to be of any importance. Our conclusion is that the results based on magnetic field measurements give some support to the hypothesis that magnetic fields exposure may play a role in the development of brain tumours.     

Occupational exposure to power frequency magnetic fields and risk of non-Hodgkin lymphoma

Objectives

To investigate the risk of non‐Hodgkin lymphoma (NHL) using a job‐exposure matrix (JEM) to assess exposure to occupational magnetic fields at the power frequencies of 50/60 Hz.

Methods

The study population consisted of 694 cases of NHL, first diagnosed between 1 January 2000 and 31 August 2001, and 694 controls from two regions in Australia, matched by age, sex and region of residence. A detailed occupational history was given by each subject. Exposure to power frequency magnetic fields was estimated using a population‐based JEM which was specifically developed in the United States to assess occupational magnetic field exposure. The cumulative exposure distribution was divided into quartiles and adjusted odds ratios were calculated using the lowest quartile as the referent group.

Results

For the total work history, the odds ratio (OR) for workers in the upper quartile of exposure was 1.48 (95% CI 1.02 to 2.16) compared to the referent (p value for trend was 0.006). When the exposure was lagged by 5 years the OR was 1.59 (95% CI 1.07 to 2.36) (p value for trend was 0.003). Adjusting for other occupational exposures did not significantly alter the results.

Conclusions

These findings provide weak support for the hypothesis that occupational exposure to 50/60 Hz magnetic fields increases the risk of NHL.     

Occupational exposure to magnetic fields in case-referent studies of neurodegenerative diseases

OBJECTIVES: Case-referent studies of Alzheimer's disease, amyotrophic lateral sclerosis, and Parkinson's disease were conducted to explore the relationship between these neurodegenerative diseases and occupational exposure to magnetic fields. Three methods of exposure assessment were used for the comparison, and the consistency of findings between these approaches was evaluated. METHODS: Separate case-referent sets were formed from among recorded deaths of males in the state of Colorado for the years 1987 through 1996. The following three methods of exposure assessment were used: a dichotomous grouping of electrical versus nonelectrical occupations, a three-tiered grouping of potential magnetic-field exposure based on a combination of job title and industry, and categories of exposure based on the means of the magnetic fields estimated from a job-exposure matrix. RESULTS: A positive association was observed for Parkinson's disease with all the methods of magnetic-field exposure assessment, the odds ratio (OR) for the highest category in the job-exposure matrix being 1.50 [95% confidence interval (95% CI) 1.02-2.19]. Amyotrophic lateral sclerosis was associated with a history of electrical occupations (OR 2.30, 95% CI 1.29-4.09) but not with magnetic-field exposure as estimated by the job-exposure matrix. No consistent associations with magnetic fields were observed for Alzheimer's disease. CONCLUSIONS: This study provides some support for an association between occupational magnetic-field exposure and Parkinson's disease, but the findings are novel and require replication. Associations with the other neurodegenerative diseases were inconsistent and dependent on the method of exposure assessment.     

Glossary of terms used when discussing exposure to electric and magnetic fields

This glossary defines and discusses terms used when discussing exposure to electric and magnetic fields.     

Occupational exposure to low frequency magnetic fields and dementia: a case-control study

Background

Several studies point to a potential aetiological relevance to dementia of exposure to low‐frequency magnetic fields, but the evidence is inconclusive.

Objective

To further examine the relationship between low frequency magnetic fields and dementia.

Methods

From 23 general practices, 195 patients with dementia were recruited. Of these, 108 had possible Alzheimer''s disease, 59 had possible vascular dementia and 28 had secondary or unclassified dementia. A total of 229 controls were recruited: 122 population controls and 107 ambulatory patients free from dementia. Data were gathered in a structured personal interview; in cases, the interview was administered to the next of kin. Exposure to low‐frequency electromagnetic fields was assessed by expert rating. To identify occupations suspected to be associated with dementia, major occupations were a priori formed. Odds ratios were calculated using logistic regression, to control for age, region, sex, dementia in parents and smoking.

Results

Exposure to magnetic fields was not significantly associated with dementia; restriction of the analysis to cases with possible Alzheimer''s disease or possible vascular dementia did not lead to statistically significant results. We found an increased risk of dementia in blue‐collar occupations (electrical and electronics workers, metal workers, construction workers, food and beverage processors and labourers).

Conclusions

Our study does not support a strong association between occupational exposure to low‐frequency magnetic fields and dementia. Further studies should consider the relationship between blue‐collar work and the late development of dementia.Alzheimer''s dementia and vascular dementia are the two major forms of dementia in elderly people. Some recent epidemiological studies have analysed the role of low‐frequency magnetic fields in the aetiology of dementia. On the basis of mortality studies, the evidence is equivocal: several,^1,2,3,4 but not all,^5,6 death certificate‐based studies—partly showing considerable overlap in the study populations—find a significant association between exposure to magnetic fields and dementia.Most case–control studies show an association between occupational exposure to magnetic fields and dementia,^7,8,9,10 two case–control studies do not confirm the relationship between exposure to magnetic fields and dementia¹¹ or cognitive impairment.¹² Recently, a prospective cohort study conducted in the Kungsholmen district of Stockholm¹³ found a relationship between exposure to electromagnetic fields in the lifetime principal job and Alzheimer''s disease in men, but not in women.As a pathophysiological explanation of the potential association between exposure to magnetic fields and Alzheimer''s disease, Sobel and Davanipour¹⁴ hypothesise the following mechanism: initiated by increased intracellular calcium ion levels in some cell systems, soluble amyloid β production might increase (eg, in skin cells). Apolipoproteins E and J might bind to the soluble amyloid β in blood and might therefore assist in its crossing the blood–brain barrier. A cascade of further events might lead to the formation of insoluble neurotoxic β‐pleated sheets of amyloid fibril, senile plaques and eventually Alzheimer''s disease.¹⁴ Analysing blood and urine samples of male electric utility workers, Noonan et al¹⁵ found a weak relationship between mean exposure to magnetic fields and the concentration of soluble amyloid β in the blood, which was not statistically significant. Therefore, the pathophysiological pathway by which dementia might be linked with exposure to magnetic fields still remains unclear.The aim of this case–control study is to further examine the relationship between electromagnetic fields assessed by expert rating and dementia. Furthermore, the present study intends to identify occupations suspected to be associated with the risk for lymphoma.     

Occupational exposure to radiofrequency electromagnetic fields

High exposures to radiofrequency electromagnetic fields (RF EMF) are possible in workplaces involving sources used for broadcasting, telecommunication, security and identification, remote sensing and the heating and drying of goods. A systematic literature review of occupational RF EMF exposure measurements could help to clarify where more attention to occupational safety may be needed. This review identifies specific sources of occupational RF EMF exposure and compares the published maximum exposures to occupational exposure limits. A systematic search for peer-reviewed publications was conducted via PubMed and Scopus. Relevant grey literature was collected via web searches. For each publication, the highest measured electric field strength, magnetic flux density or power density was extracted. Maximum exposures exceeding the limits were reported for dielectric heating, scanners for security and radiofrequency identification, plasma devices and broadcasting and telecommunication transmitters. Occupational exposure exceeding the limits was rare for microwave heating and radar applications. Some publications concerned cases studies of occupational accidents followed by a medical investigation of thermal health effects. These were found for broadcasting antennas, radar installations and a microwave oven and often involved maintenance personnel. New sources of occupational exposure such as those in fifth generation telecommunication systems or energy transition will require further assessment.     

Occupational exposure to extremely low frequency magnetic fields and mortality from cardiovascular disease

The authors evaluated the relation between occupational exposure to extremely low frequency (ELF) magnetic fields and mortality from cardiovascular diseases. The study was based on 27,790 subjects from the Swedish Twin Registry. Exposure to ELF magnetic fields was assessed by linking occupation reported in 1967 or 1973 to a job exposure matrix. Four levels of exposure were related to cause-specific mortality through 1996, and primary and contributing causes of death were considered. The authors estimated relative risks by Cox regression, with adjustment for several cardiovascular disease risk indicators. The authors calculated the synergy index to evaluate potential interaction between exposure to ELF magnetic fields (>0.2 microT) and genetic susceptibility to acute myocardial infarction (AMI). Arrhythmia-related death, ischemic heart disease other than AMI, and atherosclerosis showed no association with ELF magnetic fields. The authors found a low-level increase in AMI risk in the highest exposure group (relative risk=1.3, 95% confidence interval: 0.9, 1.9) and suggestions of an exposure-response relation (p=0.02). A synergy index of 2.7 (95% confidence interval: 1.1, 6.6) in monozygotic twins indicated that the risk of AMI was strengthened among ELF magnetic field-exposed subjects with genetic susceptibility to the disease. The results for AMI corroborate previous findings from the United States. The unusual opportunity to include genetic susceptibility in the present analyses showed that evaluations of effect modification in vulnerable subjects are warranted in ELF magnetic field research.     

Occupational exposure to 50 Hz magnetic fields in workers employed in various jobs

BACKGROUND: Information on occupational exposure to ELF magnetic fields (MF) in workers is largely insufficient, and is mostly based on results obtained in Scandinavian countries and North America. Accordingly, the collection of further data is needed, especially in workers exposed in other countries, including in Italy. METHODS: One hundred and fifty workers (84 males and 66 females) employed in 28 different jobs in the Emilia-Romagna Region of Italy were examined. Individual exposure was measured using personal monitors worn on the hip in a belted pouch during three whole work-shifts (8 hours each) of a normal working week. A sampling interval of 10 seconds was adopted, resulting in the collection of more than 8600 measurements for each worker. The individual Time-Weighted Average (TWA) occupational exposure of workers was calculated as the arithmetic mean of all measurements during each work-shift. Environmental non-occupational exposure was also measured. RESULTS: The 50 degrees percentile of individual TWA in the whole group was 0.15 microT, and the 5 degrees - 95 degrees percentile was respectively 0.02-1.45 microT. Job-related exposure (expressed as the mean of the TWA measured in all workers engaged in that job) was highest in substation electric power plant workers (1.12 microT) and in sewing machine workers (0.84 microT), but was lower than 0.2 microT in more than the 70% of the examined jobs. Considering the geometric mean of individual TWA are 27 out of 28 the jobs inducing an exposure lower than 0.2 microT. The lowest exposure was observed in infant school teachers. A high variability was observed among different workers engaged in the same occupation, mainly in substation electric power plant workers, machine testers and grinders in the engineering industry and in sewing machine workers and quality control in garment production. A marked variability of the pattern of exposure during the work-shift was also observed The overall environmental (non-occupational) exposure was 0.044 microT, and individual exposure was lower than 0.2 microT in about 97% of the examined subjects. Occupational exposure was usually higher and was not correlated with environmental exposure. CONCLUSIONS: The results show that the occupational component of overall exposure must be considered in studies on the biological effects of ELF-MF in populations. The high variability observed among workers engaged in the same occupation and the variability of the pattern of exposure certainly constitute major problems and could be a cause of the scarce coherence of the results of epidemiological studies on biological effects of ELF-MF to date. An improvement in protocols for the evaluation of exposure in workers, including the use of personal monitoring, is certainly needed.     

Occupational exposure to static, ELF, VF and VLF magnetic fields and immune parameters

Despite the important role of the immune system in defending the body against infections and cancer, very few investigations have been undertaken to study possible effects of electromagnetic fields on human immunity. The aim of the present study was to examine the effect of occupational exposure on hospital personnel operating magnetic resonance tomographs and on industrial workers at induction heaters. In both categories of workplaces, magnetic flux densities exceeding Austrian exposure standards have been registered. Because of the complexity and high redundancy of the immune system, an extensive range of assay systems was applied: relative and absolute numbers of lymphocytic subsets were counted, the proliferative activity of T and B cells determined, the production of interleukin 2, interferon gamma and tumour necrosis factor alpha analysed, serum immunoglobulins evaluated, as well as non-specific immunity of monocytes and granulocytes measured by their oxidative burst. The number of natural killer cells and oxidative burst in monocytes showed statistically significant differences in workers at induction heaters and controls. The observed effect on oxidative burst was counteracted by a higher number of active cells in the exposed group, indicating normal non-specific immunity. The high number of natural killer cells, observed in some of the study subjects working at induction heaters, was reconfirmed in another investigation and deserves a further follow-up.     

Candidate sites of action for microdosimetry associated with exposure to extremely-low-frequency magnetic fields,electric fields and contact currents

Recent advances enable one to apply numerical techniques to anatomically-correct human models to compute current densities and electric fields in tissue due to exposure to electric fields, magnetic fields, or contact currents. These methods have proved to be informative in estimating exceedance of basic restrictions prescribed by exposure guideline organizations. To date, the analyses have been conducted with a resolution on the order of millimeters. However, these techniques have future roles to play at higher levels of resolution at those sites in target tissues suspected of transducing local electric fields into biological responses. Two specific cases in which high resolution "microdosimetry" would yield value involve (a) residential settings and childhood leukemia and (b) worker exposure and cardiovascular disease. Recent research suggests that residential contact currents on the order of microamperes can produce biologically significant dose (expressed as the local electric field) to the bone marrow of a child. Microdosimetry would focus on pluripotent progenitor cells resident in the marrow compartment, as well as anatomic features that distinguish a child's from an adult's marrow. Laboratory and epidemiologic research has suggested that magnetic field exposure may affect heart rate variability, a measure reflective of autonomic nervous system control of cardiac activity. Given the physical attributes of the central nervous system and the sites that could serve as substrates for field interactions, future microdosimetry addressing heart rate variability effects may be well-advised to focus on the electrically excitable dendritic arborizations of neurons. In both cases, microdosimetry will help shed light on primary interactions in tissue.     

Occupational exposure to electromagnetic fields and risk of Alzheimer's disease

BACKGROUND: Extremely-low-frequency magnetic field (ELF-MF) exposure is suspected to increase the risk of Alzheimer's disease. Such fields are present in the vicinity of electrical motors and other electric appliances containing coils. METHODS: We investigated lifetime occupational ELF-MF exposure in relation to Alzheimer's disease and dementia among a community dementia-free cohort (n = 931) age 75 years and older in Stockholm, Sweden. This cohort was followed from 1987-1989 until 1994-1996 to detect dementia cases (Diagnostic and Statistical Manual of Mental Disorders, revised 3rd edition criteria). Information on lifetime job history was obtained by interview, usually of next of kin. ELF-MF exposure was assessed using a job-exposure matrix, measurement on historical equipment, and expert estimation. We analyzed the data with Cox models controlling for potential confounders. RESULTS: Dementia was diagnosed in 265 subjects, including 202 with Alzheimer's disease. Among men, ELF-MF exposure > or=0.2 microT in lifetime principal job was related to multivariate-adjusted relative risks of 2.3 (95% CI = 1.0-5.1) for Alzheimer's disease and 2.0 (1.1-3.7) for dementia. We found no association among women. A similar sex-specific pattern was seen for the associations with average ELF-MF exposure throughout the work life. A dose-response relation was suggested in men, with multivariate-adjusted relative risks of 2.4 (0.8-6.8) for Alzheimer's disease and 2.5 (1.1-5.6) for dementia for the upper tertile of lifetime average exposure. CONCLUSIONS: Long-term occupational exposure to a higher ELF-MF level may increase the risk of Alzheimer's disease and dementia in men. Similar patterns were not seen in women, which may in part be the result of a greater exposure misclassification in women than in men.     

血站采血护士职业暴露与防护

目的分析血站采血护士职业暴露的危险因素,并探讨有效的防护措施。方法对血站采血护士职业暴露的原因、方式、危险程度及防护方法进行分析。结果采血时环境拥挤,互相碰撞;长时间工作或一人同时为2名献血者采血;操作中双手回套针头,护针帽脱落,传递过程中被带血针头刺伤及采集小样针头放置不当,易导致采血护士针刺伤。2006年未设置防刺破试管座前,采血护士针刺伤发生率为80%;采用不锈钢试管座后未再发生针刺伤。结论采血护士易受职业暴露危险因素的影响,针刺伤是其职业暴露的主要方式。应加强采血护士的职业防护。     

Assessment of non-sinusoidal, pulsed, or intermittent exposure to low frequency electric and magnetic fields

The correct assessment of non-sinusoidal, pulsed, or intermittent exposure to low frequency electric and magnetic fields already is a key issue in the occupational environment while becoming more and more important in the domain of the general public. The method presented provides a simple and safe solution for the assessment of arbitrary field types--including sinusoidal and continuous-wave signals--with frequencies up to several 100 kHz and has already proven its practicability and usefulness for more than 5 years. The concept is based on fundamental laws of physics and electrostimulation and well-established physiological data. It allows for a seamless and easy integration in any standard or guideline dealing with human safety in electric, magnetic, and electromagnetic fields. A very simple-to-use graphical version allows an easy and fast assessment of the exposure to non-sinusoidal, pulsed, or intermittent low-frequency magnetic fields without introducing a large overestimation of the exposure situation. A computer-based version makes a much more detailed signal analysis possible and can provide useful information for exposure reduction using modifications of the magnetic field's time parameters (e.g., rise/fall times).