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

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.

AI evidence extraction

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

Suggested hubs

• occupational-exposure (0.9)
  Cohort of office workers exposed to strong magnetic fields from workplace transformers.

{
    "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": 0.7800000000000000266453525910037569701671600341796875,
    "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": 0.90000000000000002220446049250313080847263336181640625,
            "reason": "Cohort of office workers exposed to strong magnetic fields from workplace transformers."
        }
    ]
}

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