Assessment and grouping of occupational magnetic field exposure in five electric utility companies

Kromhout, Hans; Loomis, D.; Mihlan, GJ; Peipins, Lucy A.; Kleckner, Robert C.; Iriye, Richard; Savitz, D. A.

doi:10.5271/sjweh.7

Cited by 69 publications

(53 citation statements)

References 23 publications

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“…Data were obtained from a large historical cohort study of workers in five electric utility companies in the USA, which included a survey of occupational exposure to 60 Hz electric magnetic fields among randomly selected workers in 28 job categories (Loomis et al, 1994;Kromhout et al, 1995;Saviz and Loomis, 1995). The between-and within-group variance components were estimated, and the effect of different grouping strategies was assessed for subsequent estimation of exposure to be used in an exposure-response analysis of mortality data.…”

Section: Association Of Cancer With Electric Magnetic Field Exposurementioning

confidence: 99%

“…Next, we illustrate how a researcher may obtain valid estimates of exposure-disease associations through linear or logistic regression methods, even when exposure measurements for all subjects are not available, as long as an adequate sample of measured values for each group is drawn and the between-group variability is large. The impact of different grouping schemes on parameter estimation is illustrated in two examples: (a) occupational exposure to magnetic fields among workers with any cancer (Kromhout et al, 1995;Saviz and Loomis, 1995) and (b) respiratory health of employees in the European carbon black manufacturing industry in relation to exposure to carbon black dust (van Tongeren et al, 1997). In section 2, we present the bias equations for individual-and group-based assessments for both random and FGE models.…”

Section: Introductionmentioning

confidence: 99%

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Bias in the estimation of exposure effects with individual- or group-based exposure assessment

Kim

Richardson

Loomis

et al. 2010

J Expo Sci Environ Epidemiol

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In this paper, we develop models of bias in estimates of exposure-disease associations for epidemiological studies that use group-and individual-based exposure assessments. In a study that uses a group-based exposure assessment, individuals are grouped according to shared attributes, such as job title or work area, and assigned an exposure score, usually the mean of some concentration measurements made on samples drawn from the group. We considered bias in the estimation of exposure effects in the context of both linear and logistic regression disease models, and the classical measurement error in the exposure model. To understand group-based exposure assessment, we introduced a quasi-Berkson error structure that can be justified with a moderate number of exposure measurements from each group. In the quasi-Berkson error structure, the true value is equal to the observed one plus error, and the error is not independent of the observed value. The bias in estimates with individual-based assessment depends on all variance components in the exposure model and is smaller when the between-group and between-subject variances are large. In group-based exposure assessment, group means can be assumed to be either fixed or random effects. Regardless of this assumption, the behavior of estimates is similar: the estimates of regression coefficients were less attenuated with a large sample size used to estimate group means, when between-subject variability was small and the spread between group means was large. However, if groups are considered to be random effects, bias is present, even with large number of measurements from each group. This does not occur when group effects are treated as fixed. We illustrate these models in analyses of the associations between exposure to magnetic fields and cancer mortality among electric utility workers and respiratory symptoms due to carbon black.

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Section: Association Of Cancer With Electric Magnetic Field Exposurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Bias in the estimation of exposure effects with individual- or group-based exposure assessment

Kim

Richardson

Loomis

et al. 2010

J Expo Sci Environ Epidemiol

View full text Add to dashboard Cite

show abstract

“…24,25 Exposure to EMFs was estimated by an assessment of exposure to magnetic fields, focusing on the time-weighted average, as described in detail elsewhere and briefly summarized here. 19,[26][27][28] Complete work histories were abstracted and computerized. To consolidate thousands of job titles at the 5 participating companies, 28 occupational categories were constructed based on work activities, responsibilities, and exposure potential 26 to define the rows of a job exposure matrix.…”

mentioning

confidence: 99%

“…A total of 2,842 usable measurements was obtained and used to compute time-weighted average exposures and arithmetic means for each occupational category in the job exposure matrix. 27,28 Cells for exposure to magnetic fields were rank ordered and collapsed into 5 groups to increase statistical precision. Grouping was based on the distribution of the arithmetic mean exposure of each occupational category measured successfully in each company.…”

mentioning

confidence: 99%

“…Each of the combinations of company and occupational category was placed in 1 of the 5 levels of the job exposure matrix according to the estimated level of exposure to magnetic fields. 28 The average group exposures were assigned for each occupational category and summed over employment intervals for each worker. The mean exposures in each calendar year were summed and multiplied by the proportion of all hours spent at work (0.23) to yield workday exposure in microtesla-days and divided by 365 to yield microtesla-years of occupational exposure.…”

mentioning

confidence: 99%

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Exposure to electromagnetic fields and suicide among electric utility workers: a nested case-control study

Wijngaarden

Savitz²,

Kleckner³

et al. 2000

Western Journal of Medicine

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ⅷ Objective To examine mortality from suicide in relation to estimated exposure to extremely low-frequency electromagnetic fields in a cohort of 138,905 male electric utility workers. ⅷ Methods Casecontrol sampling, which included 536 deaths from suicide and 5,348 eligible controls. Exposure was classified based on work in the most common jobs with increased exposure to magnetic fields and indices of cumulative exposure to magnetic fields based on a measurement survey. ⅷ Results Suicide mortality was increased relative to work in exposed jobs and with indices of exposure to magnetic fields. Increased odds ratios (ORs) were found for years of employment as an electrician (OR, 2.18; 95% confidence interval [CI], 1.25-3.80) or line worker (OR, 1.59; 95% CI, 1.18-2.14), whereas a decreased OR was found for power plant operators (OR, 0.67; 95% CI, 0.33-1.40). A dose-response gradient with exposure to magnetic fields was found for exposure in the previous year, with a mortality OR of 1.70 (95% CI, 1.00-2.90) in the highest exposure category. Stronger associations, with ORs in the range of 2.12 to 3.62, were found for men younger than 50 years. ⅷ Conclusions These data provide evidence for an association between occupational electromagnetic fields and suicide that warrants further evaluation. A plausible mechanism related to melatonin and depression provides a direction for additional laboratory research and epidemiologic evaluation.

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Lymphoma and multiple myeloma mortality in relation to magnetic field exposure among electric utility workers

Schroeder

Savitz

1997

Am. J. Ind. Med.

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Associations between occupational magnetic field exposure and non‐Hodgkin's lymphoma (NHL), Hodgkin's disease, and multiple myeloma mortality were evaluated in 138,905 electrical utility workers. A job‐exposure matrix based on measured magnetic fields was used to derive individual exposure estimates. There was a small positive association between all NHL and low‐grade NHL and duration of employment in any magnetic field‐exposed job, but only up to 20 years. Cumulative magnetic field exposure was associated with a rising, then falling, risk of NHL. Rate ratios for intermediate/high‐grade lymphoma were increased for the highest levels of lifetime cumulative exposure (RR = 3.7 and RR = 2.3), and were most pronounced for those exposures occurring 10–20 years previously. Hodgkin's disease and multiple myeloma mortality did not appear to be associated with exposure. Associations were stronger for NHL subgroups, suggesting that further analysis by subgroup may be warranted, but the absence of dose‐response gradients diminishes the likelihood that associations represent causal relationships. Am. J. Ind. Med. 32:392–402, 1997. © 1997 Wiley‐Liss, Inc.

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Assessment and grouping of occupational magnetic field exposure in five electric utility companies

Abstract: The following article refers to this text: 2018;44(1):1-110

Cited by 69 publications

References 23 publications

Bias in the estimation of exposure effects with individual- or group-based exposure assessment

Bias in the estimation of exposure effects with individual- or group-based exposure assessment

Exposure to electromagnetic fields and suicide among electric utility workers: a nested case-control study

Lymphoma and multiple myeloma mortality in relation to magnetic field exposure among electric utility workers

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