Task-based estimation of past exposures to 60-hertz magnetic and electric fields at an electrical utility.

Scandinavian journal of work, environment & health · 1997 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 4130

Study snapshot

PublicationScandinavian journal of work, environment & health · 1997

Study typeexposure_assessment

Reported directionUnclear

Evidence ratingInsufficient

Abstract

OBJECTIVES: Past exposures of electric utility workers to extremely low-frequency (ELF) magnetic (B) and electric fields (E) in Quebec were estimated. METHODS: The current intensities were measured and durations of exposures determined for tasks or work locations in 14 job categories. Past task or location intensities were extrapolated from the present on the basis of interviews with long-term workers and utility personnel. Past task or location durations were estimated for the long-term workers. Time-weighted average (TWA) exposures for past periods were reconstructed for jobs from the intensity and duration estimates. RESULTS: Magnetic fields were estimated to have increased the most over time for substation and distribution-line jobs. Magnetic field exposures for jobs in the generation and transmission of electricity were estimated to have increased very little. For substation jobs, the ratios of magnetic fields in 1945 to those in 1990 ranged from 0.42 to 0.69; the corresponding figures for distribution-line jobs ranged from 0.36 to 0.94. For electric fields in substations, the estimated increase over time was less than for magnetic fields, the 1945:1990 ratios ranging from 0.59 to 0.88. For the distribution line jobs, the 1945:1990 ratios for electric fields were less than 1.0 in 4 cases (0.6 to 0.89), more than 1.0 in 3 others (1.13 to 2.01) and unchanged in 1. CONCLUSIONS: Reconstruction of TWA exposures allowed changes in the intensity and the duration of exposures to be considered separately. Documentation of the intensity and duration of exposures for different tasks allows exposure reconstruction for jobs that have ceased to exist. The method is applicable elsewhere if exposure-monitoring records allow the level and duration of exposures for tasks or locations to be calculated and if estimates of past durations and intensities of exposures can be reliably obtained.

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AI evidence extraction

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Study typeexposure_assessment

Effect directionunclear

PopulationElectric utility workers in Quebec (14 job categories)

Sample sizeNot supplied

ExposureELF · Past periods reconstructed (e.g., 1945 vs 1990) using task/location durations

Evidence strengthInsufficientConfidence: 78% · Peer reviewed: yes

Main findings

Using present-day measurements plus interviews to extrapolate past task/location intensities and durations, the authors reconstructed past TWA exposures for 14 utility job categories. Estimated magnetic-field exposures increased most over time for substation and distribution-line jobs (1945:1990 B-field ratios 0.42–0.69 for substation jobs; 0.36–0.94 for distribution-line jobs), while generation and transmission jobs changed little. Electric-field increases in substations were smaller than for magnetic fields (1945:1990 ratios 0.59–0.88); for distribution-line jobs, electric-field ratios were <1.0 in four cases (0.6–0.89), >1.0 in three (1.13–2.01), and unchanged in one.

Outcomes measured

Task/location-specific magnetic field (B) intensities
Task/location-specific electric field (E) intensities
Reconstructed time-weighted average (TWA) exposures over past periods
Changes in estimated exposure intensity and duration over time by job category

Limitations

Past task/location intensities were extrapolated from present measurements based on interviews with long-term workers and utility personnel (potential recall/estimation uncertainty).
Past task/location durations were estimated for long-term workers; accuracy depends on reliability of these estimates.
Applicability depends on availability of exposure-monitoring records and ability to reliably estimate past durations and intensities.

View raw extracted JSON

{
  "study_type": "exposure_assessment",
  "exposure": {
    "band": "ELF",
    "source": "occupational",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": "Past periods reconstructed (e.g., 1945 vs 1990) using task/location durations"
  },
  "population": "Electric utility workers in Quebec (14 job categories)",
  "sample_size": null,
  "outcomes": [
    "Task/location-specific magnetic field (B) intensities",
    "Task/location-specific electric field (E) intensities",
    "Reconstructed time-weighted average (TWA) exposures over past periods",
    "Changes in estimated exposure intensity and duration over time by job category"
  ],
  "main_findings": "Using present-day measurements plus interviews to extrapolate past task/location intensities and durations, the authors reconstructed past TWA exposures for 14 utility job categories. Estimated magnetic-field exposures increased most over time for substation and distribution-line jobs (1945:1990 B-field ratios 0.42–0.69 for substation jobs; 0.36–0.94 for distribution-line jobs), while generation and transmission jobs changed little. Electric-field increases in substations were smaller than for magnetic fields (1945:1990 ratios 0.59–0.88); for distribution-line jobs, electric-field ratios were <1.0 in four cases (0.6–0.89), >1.0 in three (1.13–2.01), and unchanged in one.",
  "effect_direction": "unclear",
  "limitations": [
    "Past task/location intensities were extrapolated from present measurements based on interviews with long-term workers and utility personnel (potential recall/estimation uncertainty).",
    "Past task/location durations were estimated for long-term workers; accuracy depends on reliability of these estimates.",
    "Applicability depends on availability of exposure-monitoring records and ability to reliably estimate past durations and intensities."
  ],
  "evidence_strength": "insufficient",
  "confidence": 0.78,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "extremely low-frequency",
    "ELF",
    "60-hertz",
    "magnetic fields",
    "electric fields",
    "occupational exposure",
    "electric utility workers",
    "exposure reconstruction",
    "time-weighted average",
    "task-based assessment",
    "substation",
    "distribution line",
    "generation",
    "transmission"
  ],
  "suggested_hubs": [
    {
      "slug": "occupational-exposure",
      "weight": 0.9,
      "reason": "Exposure reconstruction for electric utility workers across job categories."
    }
  ]
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.5271/sjweh.267
PubMed: 9476808

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