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 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 lead and blood pressure: a study in 105 workers

A group of workers, occupationally exposed to lead and cadmium compounds (n = 53), was compared to a group of workers not exposed to these metals (n = 52). The average values of systolic, diastolic, and mean blood pressure were found to be higher in the exposed group (p less than 0.05). In contrast with the correlation between CdU and blood pressure, the correlation between PbB and systolic and mean blood pressure remained statistically significant after controlling for age and pulse rate (r = 0.22, p less than 0.05). The prevalence of potential hypertension (defined as systolic blood pressure greater than or equal to 160 mm Hg and/or diastolic blood pressure greater than or equal to 95 mm Hg and/or under treatment for hypertension) was higher in the exposed group, but the observed relative risk was not statistically significant: relative risk = 1.91 (95% confidence limits, 0.90-4.05). Furthermore, a significant correlation between PbB and Hgb (r = -0.28, p = 0.004) was observed. Differences in kidney function, as assessed in this study, were not detected.     

A personal monitoring study to assess workplace exposure to environmental tobacco smoke.

We enrolled 15 nonsmoking volunteers to evaluate the feasibility of measuring personal exposure to environmental tobacco smoke (ETS) at work and to characterize workplace exposures. During one workshift, we obtained questionnaires on exposure, saliva and urine for cotinine, and personal air samples for respirable particles and nicotine. The levels of cotinine, respirable particles, and nicotine varied widely with self-reports of exposure to ETS, but on average increased with increasing exposure.     

Occupational exposures to extremely low frequency magnetic fields and postmenopausal breast cancer

BACKGROUND: The association between occupational exposure to extremely low frequency magnetic fields (ELF-MF) and risk of postmenopausal breast cancer was assessed in a case-control study. METHODS: Breast cancer cases were compared to cancer controls. Interviewers elicited information on risk factors and on lifetime work history. Industrial hygienists assigned to each job average duration of exposure to ELF-MF at four levels of intensities ("none," <0.2 microT; "low," 0.2-<0.5microT; "medium," 0.5-<1microT; "high," > or =1-10microT). Unconditional logistic regression was used to estimate adjusted odds ratios (OR) and 95% confidence intervals (95% CI). RESULTS: A total number of 608 cases and 667 controls participated. Adjusting for accepted breast cancer risk factors, we found an OR of 1.13 for lifetime occupational exposure to ELF-MF at medium or high intensities. Risks were larger for exposures before age 35 (OR = 1.40), and statistically significant for exposures before 35 among cases with progesterone receptor positive tumors (OR = 1.56, 95% CI=1.02-2.39). CONCLUSIONS: There appears to be a small increased risk for breast cancer among postmenopausal women exposed occupationally to ELF-MF.     

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 electromagnetic fields and acute leukaemia: analysis of a case-control study

Aims: To investigate whether the risk of acute leukaemia among adults is associated with occupational exposure to electromagnetic fields.     

Leukaemia, brain tumours and exposure to extremely low frequency magnetic fields: cohort study of Swiss railway employees

Aims

To investigate the relationship between extremely low frequency magnetic field (ELF‐MF) exposure and mortality from leukaemia and brain tumour in a cohort of Swiss railway workers.

Methods

20 141 Swiss railway employees with 464 129 person‐years of follow‐up between 1972 and 2002 were studied. Mortality rates for leukaemia and brain tumour of highly exposed train drivers (21 μT average annual exposure) were compared with medium and low exposed occupational groups (i.e. station masters with an average exposure of 1 μT). In addition, individual cumulative exposure was calculated from on‐site measurements and modelling of past exposures.

Results

The hazard ratio (HR) for leukaemia mortality of train drivers was 1.43 (95% CI 0.74 to 2.77) compared with station masters. For myeloid leukaemia the HR of train drivers was 4.74 (95% CI 1.04 to 21.60) and for Hodgkin''s disease 3.29 (95% CI 0.69 to 15.63). Lymphoid leukaemia, non‐Hodgkin''s disease and brain tumour mortality were not associated with magnetic field exposure. Concordant results were obtained from analyses based on individual cumulative exposure.

Conclusions

Some evidence of an exposure–response association was found for myeloid leukaemia and Hodgkin''s disease, but not for other haematopoietic and lymphatic malignancies and brain tumours.     

Biological monitoring of exposure to organophosphorus insecticides in a group of horticultural greenhouse workers

Exposure to selected organophosphorus insecticides (OPs), malathion, diazinon and acephate, was evaluated in a group of horticultural greenhouse workers. This was achieved through measurements of the cumulative urinary excretion time courses of specific and non-specific biomarkers over a 24 h period following the onset of work exposure. For malathion, the absorbed daily doses were estimated from the 24 h cumulative urinary amounts of the specific mono- and di-carboxylic acid metabolites (the sum of MCA and DCA) through the use of a kinetic model. The observed 24 h urinary levels were also compared with a biological reference value (BRV) of 57 nmol kg(-1) of body weight established in a previous work on the basis of a human no-observed-effect level exposure dose. Excretion values were found to be 2.5% or less of the BRV, suggesting a negligible health risk. Both median and 95th percentile concentrations of DCA (n = 57 samples) were, however, slightly higher than the baseline values determined by the Centers for Disease Control and Prevention (CDC) in the US civilian population (MCA was not analyzed by the CDC). The cumulative urinary excretion time course of the methyl phosphoric (MP) derivatives, which are metabolites of malathion but also of several other OPs, was also determined. Though relatively low, the MP levels were from 3 to 31 times higher than would be expected on the basis of the malathion specific MCA and DCA excretions, indicating that MP excretions stem from sources other than malathion exposure. Accordingly, only the time courses of MCA and DCA excretion rate (nmol h(-1)) were compatible with the time of work exposure. Urinary biomarkers of exposure to diazinon and acephate were also measured. Urinary concentrations were essentially below or equal to the analytical limit of detection of 1 microg l(-1) for 2-isopropyl-4-methyl-6-hydroxypyrimidine (n = 54) and of 0.8 microg l(-1) for acephate and methamidophos (n = 59): values within the baseline range of the US civilian population, like the observed phosphoric metabolite concentrations. The workers under study thus appeared to be only slightly more exposed to malathion than the general population. However, their overall exposure to OPs, as measured by non-specific phosphoric metabolites, was similar to that of the general population, whose exposure occurs mainly through the ingestion of contaminated food. These results question the relevance of measuring non-specific phosphoric metabolites when attempting to assess low-dose occupational exposure to a specific OP.     

A literature review: the cardiovascular effects of exposure to extremely low frequency electromagnetic fields

The effects of exposure to extremely low frequency (ELF) electromagnetic fields (EMFs) on human cardiovascular parameters remain undetermined. Epidemiological studies have utilized dosimetry estimations of employee workplace exposure using altered heart rate variability (HRV) as predictive of certain cardiovascular pathologies. Laboratory studies have focused on macrocirculatory indicators including heart rate, HRV and blood pressure. Few studies have been conducted on the response of the microcirculatory system to EMF exposure. Attempts to replicate both epidemiological and laboratory studies have been mostly unsuccessful as study design, small sample populations and confounding variables have hampered progress to date. Identification of these problems, in the current context of international exposure guideline re-evaluation, is essential for future EMF studies. These studies should address the possible deleterious health effects of EMFs as well as the detection and characterization of subtle physiological changes they may induce. Recommendations for future work include investigating the macro- and microcirculatory relationship and the use of laboratory geomagnetic shielding.     

Occupational paraquat exposure of agricultural workers in large Costa Rican farms

Objective  Paraquat is an herbicide widely used worldwide. This study determined the extent of occupational exposure to paraquat among farm workers in Costa Rica and identified determinants of occupational exposure. Methods  Twenty-four hour urine samples were collected from 119 paraquat handlers and 54 non-handlers from banana, coffee and palm oil farms. Information about herbicide handling operations was also collected. The urinary paraquat levels were determined by an enzyme-linked immunosorbent assay (ELISA) with a limit of quantification (LOQ) of 2 ng/mL. Inhalable dust and airborne paraquat levels were simultaneously measured for a subset of the participants. Results  Urinary paraquat measurements were non-detectable or very low when workers did not handle paraquat. For handlers, 83.3, 47.1 and 63.9% of the samples were below the LOQ on before-, during- and after-paraquat spray days, respectively. The arithmetic mean (±SD) of urinary paraquat level on days when workers handled paraquat was 6.3 (±10.45) μg/24 h. Paraquat exposures among handlers on spray day were significantly associated with the type of crop. Conclusion  Non-handlers had negligible urinary paraquat, while detectable paraquat exposures were observed among handlers on spray day. Urinary paraquat levels were different by crop.     

Maternal occupational exposure to extremely low frequency magnetic fields during pregnancy and childhood leukemia

BACKGROUND: Pregnancy is a target period for events that could induce childhood leukemia. There has been little attention to possible effects of maternal occupational exposure to extremely low frequency magnetic fields (ELF-MF) during pregnancy. METHODS: We conducted a population-based, case-control study of 491 incident cases of acute lymphoblastic leukemia in children 0-9 years of age, matched on age and sex to 491 healthy controls. Cases were diagnosed in the Province of Québec between 1980 and 1993. Mothers were interviewed to obtain detailed prenatal occupational history; individual exposure to ELF-MF was estimated based on a method we recently developed. We used 3 metrics for analyzing exposure: cumulative, average and maximum levels. Analyses were carried out among all study women and among working women only. RESULTS: Comparing the highest 10% of exposed mothers to the others, the risk of leukemia among offspring was moderately increased by using any metric, in all women and among working women only. The highest odds ratio of 2.5 (95% confidence interval = 1.2-5.0) was found for maximum exposure attained in an occupation (>/=0.4 microtesla). CONCLUSIONS: Our results are compatible with an increased risk of childhood leukemia among children whose mothers were exposed to the highest occupational levels of ELF-MF during pregnancy.     

Biological and environmental monitoring of occupational exposure of pharmaceutical plant workers to methotrexate

Summary The exposure of 11 pharmaceutical plant workers to methotrexate (MTX) was studied. Personal air samples were taken during the different manufacturing processes: drug compounding, vial filling, and tablet preparation. The uptake of MTX was established by the determination of MTX in urine. MTX was analyzed using the fluorescence polarization immunoassay (FPIA), a method that is frequently used for monitoring serum levels in patients treated with MTX. The FPIA method was modified in such a way that MTX could be measured quickly and efficiently in air and urine samples. MTX was detected in air samples of all workers except for those involved in the vial filling process (range: 0.8–182 g/m³; median: 10 g/m³). The highest concentrations were observed for workers weighing MTX (118 and 182 g/m³). MTX was detected in urine samples of all workers. The mean cumulative MTX excretion over 72–96 h was 13.4 g MTX-equivalents (range: 6.1–24 g MTX-equiva g MTX-equivalents (range: 6.1–24 g MTX-equivalents). lents). A significantly lower background level of 10.2 g A significantly lower background level of 10.2 g MTX-equivalents was measured in urine of 30 control persons (range: 4.9–21 g MTX-equivalents).     

发电厂作业人员工频电磁场职业暴露现况调查

目的探讨发电厂作业人员工频电磁场职业暴露现况。方法按发电量不同,抽取3家300 MW、3家600 MW、2家1 000MW共8家发电厂作为研究对象,对存在工频电磁场的作业环境进行检测,对其中作业人员进行个体磁场的测量。以我国国家标准GBZ 2.2-2007及国际非电离辐射防护委员会规定的导出限值对结果进行评估。结果对发电厂共510个点的作业环境进行了检测,电场强度的中位数为0.005 kV/m,最大值为12.080 kV/m,有6个点超过了10 kV/m,占总数1.18%,有27个点超过了5 kV/m,占5.29%;磁场强度的中位数为7.39μT,最大值为318.00μT,有15个点超过100μT,占2.94%。其中电场强度超过5kV/m的点均在高压输电线下方(包括主变的出线端及升压站的室外设备)。作业人员工频磁场日暴露水平在0.80~1.36μT之间。结论发电厂作业人员在高压输电线下方作业时有短时接触高剂量工频电场的危险。     

Occupational exposure levels to benzene in Italy: findings from a national database

Purpose  

Benzene is classified as human carcinogen and the association with lymphohaematopoietic cancer has been observed in many occupational epidemiological studies. The aim of this study is to summarize data about occupational exposure levels to benzene in Italy.     

Comparison of extremely low frequency (ELF) magnetic field personal exposure monitors

The MultiWave System III (MW III), a recently developed personal monitor for extremely low frequency (ELF) magnetic fields, was compared with the standard EMDEX Lite (Electric and Magnetic Field Digital Exposure System), the type of monitor widely used in epidemiology and other exposure assessments. The MW III captures three-axis magnetic field waveforms for the calculation of many exposure metrics, while the EMDEX monitors measure only the root-mean-squared (RMS) vector magnitude (or resultant). Thirty-eight partial period personal samples were monitored in six different job classifications. The sampling time for each personal sample ranged from 90 to 133 min, with a mean sample time of 110 min. The EMDEX Lite and MW III were evaluated by comparing the maximum and partial period time-weighted average (TWA) of the ELF magnitude. TWA exposures measured for the 38 partial period samples by the EMDEX Lite ranged from 1.2 to 65.3 mG, with a mean of 18.1 mG, while corresponding values for the MW III ranged from 1.1 to 65.8 mG, with a mean of 17.7 mG. The maximum magnetic field exposures measured for the 38 partial period personal samples by the EMDEX Lite ranged from 27.0 to 420.2 mG, with a mean of 216.3 mG, while corresponding values for the MW III ranged from 40.2 to 1311.8 mG, with a mean of 368.4 mG. The maximum and TWA ELF magnetic field exposures measured by the EMDEX Lite and MW III were compared using a two-tailed, paired t-test. Analyses indicate that there was no significant difference in the TWA magnetic field magnitude measured by the EMDEX Lite and MW III. On the other hand, the EMDEX Lite reported significantly lower (P=0.002) maximum magnetic field measurements compared to the MW III. From a detailed analysis of the time traces, the EMDEX Lite appears to measure the ELF magnitude inaccurately when the field changes rapidly over a 4-s sampling interval. The results of this comparison suggest that the standard EMDEX Lite and MW III provide similar measure of the TWA magnetic field in a variety of occupational settings and ELF magnetic field magnitudes. However, the EMDEX Lite underestimates maximum exposures when compared to the MW III.     

Occupational chronic exposure to organic solvents XVII. Ambient and biological monitoring of workers exposed to xylenes

Ambient-air and biological monitoring of occupational xylene exposure were carried out on 2 groups of workers (13 and 10 men, respectively) exposed to a mixture of xylenes during the production of paints or during spraying. Methods: Personal ambient-air monitoring was performed for one complete work shift. Blood and urine samples were collected directly at the end of the shift. Biological monitoring was based on the determination of the concentration of xylenes in blood and on the quantification of the sum of the three methylhippuric acids in urine. Results: Average xylene ambient-air concentrations were 29 ppm (production) and 8 ppm (spraying), ranging from 5 to 58 ppm and from 3 to 21 ppm, respectively. The concentrations of xylenes in blood ranged from 63 to 715 μg/l and from 49 to 308 μg/l, with average values being 380 and 130 μg/l, respectively. Accordingly, the workers engaged in paint production also excreted more methylhippuric acids in their urine (average 1221 mg/l, range 194–2333 mg/l) than did the sprayers (average 485 mg/l, range 65–1633 mg/l). Discussion: Our results as well as a literature review indicate that occupational xylene exposure on average barely exceeds the threshold limit value of 100 ppm as proposed by both American and German institutions. Biological monitoring based on the determination of xylenes in blood and of methylhippuric acids in urine provides sufficient sensitivity and specificity for occupational health surveillance. The results also confirm the current limit values (BAT values) proposed by the Deutsche Forschungsgemeinschaft for xylenes in blood (1500 μg/l) and methylhippuric acids in urine (2000 mg/l). Received: 27 May 1998 / Accepted: 3 September 1998