Occupational Magnetic Field Exposure and Myocardial Infarction Incidence

Assessment of occupational exposure to extremely low frequency magnetic fields in hospital personnel

It has been proposed that chronic exposure to extremely low frequency (ELF) magnetic fields (MF) in occupational environments could represent a risk factor for a number of disorders. Medical and technical workers in hospitals have been reported to be exposed to relatively strong ELF fields. The present work aims to characterize exposure to MF in the 5 Hz to 2 kHz frequency range in a large hospital through both instantaneous environmental measurements and personal monitoring of workers. The study was conducted in different working environments of a hospital with about 4400 employees, many of them working at two or more different work stations and consequently, exposed to MF levels that were expected to be unevenly distributed in space and time. The results indicate that: (1) The dominant frequency at the studied environments was 50 Hz (average 90.8 ± 6% of the total B value); (2) The best descriptive information on a worker's exposure is obtained from personal monitoring of volunteer workers; (3) The arithmetic averages of exposure levels obtained from the monitoring ranged from 0.03 ± 0.01 µT in nurses to 0.39 ± 0.13 µT in physiotherapists; and (4) The description of the MF environment through spot measurements in the workplace, although coherent with the data from personal monitoring, might not adequately estimate MF exposure in some professional categories.

Campos magnéticos de frequência extremamente baixa e efeitos na saúde: revisão da literatura

A partir da publicação, em 1979, dos resultados de um estudo que apontava para o aumento do risco de leucemia em crianças associado à exposição a campos magnéticos, o interesse pelo tema vem aumentando, e diversos estudos foram publicados. O objetivo desta revisão é apresentar os diferentes métodos utilizados na avaliação da exposição aos campos magnéticos de frequência extremamente baixa, bem como as dificuldades enfrentadas na quantificação dessa exposição, além de relatar os resultados de estudos epidemiológicos publicados nos últimos 10 anos. A falta de um modelo fisiopatológico que explique uma possível influência dos campos magnéticos na saúde e a dificuldade para quantificar a exposição têm sido os maiores obstáculos da pesquisa na área. Leucemia e tumores do sistema nervoso central têm sido os efeitos mais estudados. Leucemia em crianças é o desfecho mais consistentemente associado à exposição a campos magnéticos. Estudos mais recentes apontam a associação entre esclerose lateral amiotrófica e campos magnéticos.

A population-based cohort study of occupational exposure to magnetic fields and cardiovascular disease mortality

PURPOSE

This cohort study aims to examine cardiovascular disease (CVD) mortality risks among workers in occupations potentially exposed to magnetic fields (MF).

METHODS

Risks for major CVD mortality by potential job-related MF exposure were examined in a sample of U.S. workers from the National Longitudinal Mortality Study using multivariate proportional hazards models.

RESULTS

After adjustment for demographic factors, there were no significant excess risks between individuals with medium (0.15 to <0.20 microT), high (0.20 to < 0.30 microT), or very high (>/= 0.30 microT) exposure levels as compared with individuals with background exposure levels of MF (<0.15 microT) for the CVD mortality outcomes. Indirect adjustment for potential confounding by current smoking prevalence did not change the pattern of these results.

CONCLUSION

Our study does not provide evidence for an association between occupational MF exposure and CVD mortality risk.

Cardiovascular mortality and exposure to extremely low frequency magnetic fields: a cohort study of Swiss railway workers

BACKGROUND

Exposure to intermittent magnetic fields of 16 Hz has been shown to reduce heart rate variability, and decreased heart rate variability predicts cardiovascular mortality. We examined mortality from cardiovascular causes in railway workers exposed to varying degrees to intermittent 16.7 Hz magnetic fields.

METHODS

We studied a cohort of 20,141 Swiss railway employees between 1972 and 2002, including highly exposed train drivers (median lifetime exposure 120.5 muT-years), and less or little exposed shunting yard engineers (42.1 muT-years), train attendants (13.3 muT-years) and station masters (5.7 muT-years). During 464,129 person-years of follow up, 5,413 deaths were recorded and 3,594 deaths were attributed to cardio-vascular diseases. We analyzed data using Cox proportional hazards models.

RESULTS

For all cardiovascular mortality the hazard ratio compared to station masters was 0.99 (95%CI: 0.91, 1.08) in train drivers, 1.13 (95%CI: 0.98, 1.30) in shunting yard engineers, and 1.09 (95%CI: 1.00, 1.19) in train attendants. Corresponding hazard ratios for arrhythmia related deaths were 1.04 (95%CI: 0.68, 1.59), 0.58 (95%CI: 0.24, 1.37) and 10 (95%CI: 0.87, 1.93) and for acute myocardial infarction 1.00 (95%CI: 0.73, 1.36), 1.56 (95%CI: 1.04, 2.32), and 1.14 (95%CI: 0.85, 1.53). The hazard ratio for arrhythmia related deaths per 100 muT-years of cumulative exposure was 0.94 (95%CI: 0.71, 1.24) and 0.91 (95%CI: 0.75, 1.11) for acute myocardial infarction.

CONCLUSION

This study provides evidence against an association between long-term occupational exposure to intermittent 16.7 Hz magnetic fields and cardiovascular mortality.

Mortality from Neurodegenerative Disease and Exposure to Extremely Low-Frequency Magnetic Fields: 31 Years of Observations on Swiss Railway Employees

AIMS

The objective of the present study was to investigate the relationship between extremely low-frequency magnetic field (ELF-MF) exposure and mortality from several neurodegenerative conditions in Swiss railway employees.

METHODS

We studied a cohort of 20,141 Swiss railway employees with 464,129 person-years of follow-up between 1972 and 2002. For each individual, cumulative exposure was calculated from on-site measurements and modelling of past exposure. We compared cause-specific mortality in highly exposed train drivers (mean exposure: 21 microT) with less exposed occupational groups (for example station masters: 1 microT).

RESULTS

The hazard ratio for train drivers compared to station masters was 1.96 [95% confidence interval (CI) = 0.98-3.92] for senile dementia and 3.15 (95% CI = 0.90-11.04) for Alzheimer's disease. For every 10 microT years of cumulative exposure senile dementia mortality increased by 5.7% (95% CI = 1.3-10.4), Alzheimer's disease by 9.4% (95% CI = 2.7-16.4) and amyotrophic lateral sclerosis by 2.1% (95% CI = -6.8 to 11.7). There was no evidence for an increase in mortality from Parkinson's disease and multiple sclerosis.

CONCLUSIONS

This study suggests a link between exposure to ELF-MF and Alzheimer's disease and indicates that ELF-MF might act in later stages of the disease process.

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.

Vibration exposure and myocardial infarction incidence: the VHEEP case–control study

OBJECTIVES

The main objectives of this study were to assess the risk of contracting first episode of myocardial infarction (MI) subsequent to vibration exposure and to assess a possible exposure-response relationship.

METHODS

The Västernorrland heart epidemiology programme (VHEEP, a part of the Stockholm heart epidemiology programme study) was the source of the data. VHEEP is a population-based case-control study of risk factors for acute MI. Exposure information was collected by questionnaire and vibration exposure was assessed in 218 cases and 257 controls. Relative risks were estimated using odds ratios (ORs) from binary logistic regression.

RESULTS

The results show that the OR of acute MI when exposed to vibration was 1.6 (95% CI: 1.1-2.4). It was not possible, however, to determine whether an exposure-response relationship was present.

CONCLUSIONS

Working entailing vibrating machines is associated with an increased risk for acute MI.

EMF and health

Electric and magnetic fields are ubiquitous in the modern society, and concerns have been expressed regarding possible adverse effects of these exposures. This review covers epidemiologic research on health effects of exposures to static, extremely low-frequency (ELF), and radio frequency (RF) fields. Research on ELF fields has been performed for more than two decades, and the methodology and quality of studies have improved over time. Studies have consistently shown increased risk for childhood leukemia associated with ELF magnetic fields, whereas ELF fields most likely are not a risk factor for breast cancer and cardiovascular disease. There are still inadequate data for other outcomes. More recently, focus has shifted toward RF exposures from mobile telephony. There are no persuasive data suggesting a health risk, but this research field is still immature with regard to the quantity and quality of available data. This technology is constantly changing and there is a need for continued research on this issue. Almost no epidemiologic data are available for static fields.