Increased incidence of cancer in a cohort of office workers exposed to strong magnetic fields.

American journal of industrial medicine · 1996 · Harm · Low evidence

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HarmLow evidencePaper 4221

Study snapshot

PublicationAmerican journal of industrial medicine · 1996

Study typecohort

Reported directionHarm

Evidence ratingLow

Abstract

A small cohort of 410 office workers (263 men and 147 women, ever employed) exposed to strong magnetic fields by three 12 kV transformers located beneath their first-floor office developed eight incident cancers over a 15 year exposure period. Only one cancer was ascertained in the 254 workers employed for less than 2 years, compared to seven cancer cases ascertained in the 156 workers employed for 2 years or more (p = 0.0057; Fisher's exact test). An analysis of linear trend of cancer incidence using average years employed as an exposure score was positive (p = 0.00337) with an odds ratio of 15.1 in workers employed over 5 years. A positive trend of cancer cases with duration of employment is seen for males and females separately and together (p < 0.05). For workers employed more than 2 years, the standardized cancer incidence ratio was 389 (95% confidence interval 156-801). Cumulative magnetic field exposure may be of etiologic importance in explaining the cancer incidence pattern in this cohort.

Machine Enhanced Logic

AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typecohort

Effect directionharm

PopulationOffice workers exposed to strong magnetic fields from three 12 kV transformers located beneath their first-floor office

Sample size410

ExposureELF · 15 year exposure period; employment duration categories (<2 years, ≥2 years, >5 years)

Evidence strengthLowConfidence: 78% · Peer reviewed: yes

Main findings

In a cohort of 410 office workers exposed to strong magnetic fields from three 12 kV transformers, eight incident cancers occurred over a 15-year exposure period. Cancer incidence was higher among workers employed ≥2 years (7/156) than among those employed <2 years (1/254) (p=0.0057), with a positive linear trend by years employed (p=0.00337) and an odds ratio of 15.1 for workers employed >5 years. For workers employed >2 years, the standardized cancer incidence ratio was 389 (95% CI 156–801).

Outcomes measured

Incident cancer
Cancer incidence (standardized incidence ratio)

Limitations

Small cohort size and small number of cancer cases (8 total)
Exposure characterized by employment duration as an exposure score; no quantitative magnetic field measurements reported in abstract
Potential confounding factors and cancer ascertainment methods not described in abstract

View raw extracted JSON

{
  "study_type": "cohort",
  "exposure": {
    "band": "ELF",
    "source": "occupational",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": "15 year exposure period; employment duration categories (<2 years, ≥2 years, >5 years)"
  },
  "population": "Office workers exposed to strong magnetic fields from three 12 kV transformers located beneath their first-floor office",
  "sample_size": 410,
  "outcomes": [
    "Incident cancer",
    "Cancer incidence (standardized incidence ratio)"
  ],
  "main_findings": "In a cohort of 410 office workers exposed to strong magnetic fields from three 12 kV transformers, eight incident cancers occurred over a 15-year exposure period. Cancer incidence was higher among workers employed ≥2 years (7/156) than among those employed <2 years (1/254) (p=0.0057), with a positive linear trend by years employed (p=0.00337) and an odds ratio of 15.1 for workers employed >5 years. For workers employed >2 years, the standardized cancer incidence ratio was 389 (95% CI 156–801).",
  "effect_direction": "harm",
  "limitations": [
    "Small cohort size and small number of cancer cases (8 total)",
    "Exposure characterized by employment duration as an exposure score; no quantitative magnetic field measurements reported in abstract",
    "Potential confounding factors and cancer ascertainment methods not described in abstract"
  ],
  "evidence_strength": "low",
  "confidence": 0.78,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "office workers",
    "occupational exposure",
    "magnetic fields",
    "transformers",
    "cancer incidence",
    "employment duration",
    "standardized incidence ratio"
  ],
  "suggested_hubs": [
    {
      "slug": "occupational-exposure",
      "weight": 0.9,
      "reason": "Cohort of office workers exposed to strong magnetic fields from workplace transformers."
    }
  ]
}

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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: 10.1002/(sici)1097-0274(199612)30:6<702::aid-ajim6>3.0.co;2-s
PubMed: 8914716

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