Magnetic Field Exposures in the Electric Utility Industry Relevant to Occupational Guideline Levels

Bracken, T. Dan; Senior, R.S.; Rankin, Richard F.; Bailey, Warren; Kavet, Robert

doi:10.1080/1047322x.1997.10387760

Cited by 14 publications

(8 citation statements)

References 9 publications

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“…(32;33) Epidemiological research has recently begun to address the question of potential effects of EMF on the development of chronic neurodegenerative diseases such as Alzheimer's disease and amyotrophic lateral sclerosis, but this research has not yielded any de nitive insights and is considered inadequate for "interpreting the possibility of an association." (34) Utility workers in the United States are generally exposed to elds below 10 microtesla (¹T), (19) and exposures in the community are very much lower. (35) Given these facts, the literature suggests that adverse effects of EMF on neural systems need to be examined at higher levels of exposure, if effects are to be found.…”

Section: Community Studiesmentioning

confidence: 99%

“…(19) Other studies have targeted speci c occupations and tasks to quantify and better understand the frequency and nature of guideline-level exposures. (131) The most likely candidates for high exposures are occupations within the electric-utility industry that entail work near conductors carrying large currents.…”

Section: Exposed Groupsmentioning

confidence: 99%

“…(19) Bare-hand transmissionline maintenance involves working on the conductors of an energized overhead line. The worker wears a conductive hooded suit that is electrically bonded to the energized conductor to provide shielding from electric elds.…”

Section: Exposed Groupsmentioning

confidence: 99%

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Evaluation of Biological Effects, Dosimetric Models, and Exposure Assessment Related to ELF Electric- and Magnetic-Field Guidelines

Kavet

Stuchly²,

Bailey³

et al. 2001

Applied Occupational and Environmental Hygiene

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Several organizations worldwide have issued guidelines to limit occupational and public exposure to electric and magnetic fields and contact currents in the extremely low frequency range (<3 kilohertz). In this paper, we evaluate relevant developments in biological and health research, computational methods for estimating dosimetric quantities, and exposure assessment, all with an emphasis on the power frequency (60 hertz in North America, 50 hertz in Europe). The aim of each guideline is to prevent acute neural effects of induced electric fields. An evaluation of epidemiological and laboratory studies of neurobiological effects identified peripheral nerve stimulation as the response most suitable for establishing a magnetic-field guideline. Key endpoints that merit further study include reversal of evoked potentials; cardiovascular function, as measured by heart rate and heart rate variability; and sleep patterns. High-resolution computations of induced electric fields and current densities in anatomically correct human models are now achieved with finite-difference methods. The validity and limitations of these models have been demonstrated by computations in regular geometric shapes, using both analytic and numeric computations. Calculated values for average dosimetric quantities are typically within a few percent for the two approaches. However, maximum induced quantities are considerably overestimated by numerical methods, particularly at air interfaces. Overestimates are less pronounced for the upper 99th percentile level of a dosimetric quantity, making this measure a more useful indicator of maximum dose. Neural stimulation thresholds are dependent on the electric field around the excitable cell rather than on the current density, making the former preferable for expression of basic restrictions based on nervous system function. Furthermore, modeling data indicate that the induced electric field is much less strongly influenced by tissue conductivity than is the induced current density. In the electric utility industry, most magnetic-field exposures at or near guideline levels occur in highly nonuniform fields. Two methods are described for simplified estimation of induced quantities in such fields, with each method using as input modeling results for uniform field exposure. These methods have practical value for assessing occupational exposures relative to guideline levels.

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Section: Community Studiesmentioning

confidence: 99%

Section: Exposed Groupsmentioning

confidence: 99%

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Evaluation of Biological Effects, Dosimetric Models, and Exposure Assessment Related to ELF Electric- and Magnetic-Field Guidelines

Kavet

Stuchly²,

Bailey³

et al. 2001

Applied Occupational and Environmental Hygiene

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“…A practical approach for such an assessment was not available, so we developed a statistically based monitoring and analysis methodology for evaluating the probability of exceeding magnetic-field exposure guideline levels in various scenarios [Patterson et al, 2005]. To this end, we used 60-Hz exposures in the electric-utility industry as our model since exposures in this industry have been extensively characterized [Bracken, 1993;Kavet, 1995;Bracken and Patterson, 1996;Bracken et al, 1997]. The methodology involves requirements to:…”

Section: Assessing Potential Workplace Exceedance Of Reference Levelsmentioning

confidence: 99%

Recent advances in research relevant to electric and magnetic field exposure guidelines

Kavet¹,

Bailey²,

Bracken³

et al. 2008

Bioelectromagnetics

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Limits on exposures to extremely low-frequency electric fields, magnetic fields and contact currents, designated as voluntary guidelines or standards by several organizations worldwide, are specified so as to minimize the possibility of neural stimulation. The limits, which we refer to as guidelines, derive from "basic restrictions" either on electric fields or current density within tissue, or on avoidance of annoying or startling interactions that may be experienced with spark discharge or contact current. Further, the guidelines specify more conservative permissible doses and exposure levels for the general public than for exposures in controlled environments, which most typically involve occupational settings. In 2001 we published an update on guideline science. This paper covers more recent developments that are relevant to the formulation and implementation of the next generation of guidelines. The paper deals with neurostimulation thresholds and the relevance of magnetophosphenes to setting guideline levels; dosimetry associated with contact current benchmarked against basic restrictions; tissue and cellular dosimetry from spark discharge; assessment of exposures to high electric fields in realistic situations (e.g., line worker in a transmission tower); a simplified approach to magnetic field assessment in non-uniform magnetic fields; and a quantitative approach to sampling workplace exposure for assessing compliance.

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“…(1) Both groups of workers perform tasks where exposure, on average, exceeds 0.42 mT more than 10 percent of the time and 1.0 mT for more than 5 percent of the time. Thus, for these workers and tasks, exposures above guideline levels appear to be more than momentary ones.…”

Section: Time Above Guideline Levelsmentioning

confidence: 99%

Magnetic-Field Exposures of Cable Splicers in Electrical Network Distribution Vaults

Bracken¹,

Rankin

Senior³

et al. 2001

Applied Occupational and Environmental Hygiene

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The purposes of the research reported here were to quantify the power-frequency magnetic-eld exposures of cable splicers while they were performing tasks in energized network distribution vaults and to compare these exposures with occupational exposure guideline levels. Network vaults supply electricity to commercial and residential urban areas as well as to large buildings. Participating workers wore a personal exposure monitor at the waist, kept a simple diary to record their work location, and recorded information about the vaults and tasks performed. To capture temporal variability, a stationary meter was deployed in the vault during a task. Load current in the vault was measured. To examine temporal variability over long time periods, stationary meters were deployed in selected vaults for one month. Data were collected during 77 tasks in 69 vaults for 191 persontasks, representing approximately 400 hours of in-vault personal exposure data. Highest exposures were observed in tasks performed near secondary conductors. Personal exposure variability arises principally from worker movement and activities in the vaults, not from load variability during a task. Maximum eld during a person-task exceeded the International Committee on Non-Ionizing Radiation Protection (ICNIRP) (0.42 millitesla) and the American Conference of Governmental Industrial Hygienists (ACGIH)°R (1.0 millitesla) guideline levels during 14 percent and 8 percent of the person-tasks, respectively. The mean of measurements during a person-task exceeded those guideline levels during 4 percent and 2 percent of the person-tasks, respectively. A large number of person-tasks (40%) had measured elds above the ACGIH recommended limit of 0.1 millitesla for workers with pacemakers or other implanted devices. Based on the frequency and duration of their high exposures, cable splicers working in network distribution vaults are one of the most highly exposed groups in the electric utility industry. Selective assignment of work location and task could minimize the likelihood of exposures for vault workers ex- ceeding guideline limits for wearers of pacemakers or other implanted devices. Scheduling vault tasks during off-peak hours (nights and weekends) may reduce exposures. However, even during these periods exposures in certain vaults can still exceed guideline levels.Electric utility personnel can experience power-frequency magnetic-eld exposures that approach or exceed threshold levels recommended in occupational exposure guidelines. (1) The purposes of the research reported here were to quantify the magnetic-eld exposures of cable splicers while they were performing tasks in energized network distribution vaults and to compare these exposures with guideline levels. There were no previous systematic magnetic-eld exposure data for this group of electric utility workers.Network distribution vaults supply electricity to commercial and residential urban areas, as well as to large buildings. These vaults typically house transformers where primary voltages (13.8 ...

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Magnetic Field Exposures in the Electric Utility Industry Relevant to Occupational Guideline Levels

Cited by 14 publications

References 9 publications

Evaluation of Biological Effects, Dosimetric Models, and Exposure Assessment Related to ELF Electric- and Magnetic-Field Guidelines

Evaluation of Biological Effects, Dosimetric Models, and Exposure Assessment Related to ELF Electric- and Magnetic-Field Guidelines

Recent advances in research relevant to electric and magnetic field exposure guidelines

Magnetic-Field Exposures of Cable Splicers in Electrical Network Distribution Vaults

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