Magnetic fields from indoor transformer stations and risk of cancer in adults: a cohort study

Abstract

Magnetic fields from indoor transformer stations and risk of cancer in adults: a cohort study Juutilainen J, Khan MW, Naarala J, Roivainen P. Magnetic fields from indoor transformer stations and risk of cancer in adults: a cohort study. Occup Environ Med. 2024 Nov 18:oemed-2024-109466. doi: 10.1136/oemed-2024-109466. Abstract Objectives: Studies assessing the association of adult cancers with extremely low frequency (ELF) magnetic fields (MF) have provided inconclusive results, probably affected by limitations such as low exposure levels, confounding and various forms of bias. This study investigated the association between residential ELF MF exposure and adult cancer using a design that avoids the main limitations of previous studies. Methods: Persons who have lived in buildings with indoor transformer stations during the period 1971- 2016 formed the study cohort. Their MF exposure was assessed based on the location of their apartment in relation to the transformer room. Information on their cancer diagnoses was obtained from the Finnish Cancer Registry. SIR with 95% CI was calculated to investigate the association of MF exposure with overall cancer and specific cancers. Results: The SIR for all primary sites was 1.01 (95% CI 0.93 to 1.09). An increased risk of digestive organ cancers was observed among the exposed persons, with a SIR of 1.23 (95% CI 1.03 to 1.46). The highest SIR was observed for gallbladder cancer (3.92, 95% CI 1.44 to 8.69). Increased risk of testicular cancer was observed among men exposed to MF during childhood, but this is likely to be due to confounding associated with living on the lowest floors. No other significant associations were observed for other primary cancer sites studied. Conclusions: Overall cancer risk was not affected by residential MF exposure. The increased risk of digestive organ cancers among MF-exposed persons is a novel finding requiring confirmation in further studies. WHAT IS ALREADY KNOWN ON THIS TOPIC • Extremely low frequency magnetic fields (ELF MFs) have been classified as possibly carcinogenic. The evidence is strongest for increased risk of childhood leukaemia and more inconsistent for risks of adult cancers. WHAT THIS STUDY ADDS • This study was carried out using a unique database of residential buildings with indoor transformer stations. Many limitations of previous studies could be avoided. The study suggested an association between residential MF exposure and digestive organ cancers. The overall cancer risk was not affected by MF exposure. HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY • As there is little previous evidence of an association between digestive organ cancers and MF exposure, further research on this topic is required. Compared with previous studies, this study included higher exposure levels and thus provides a useful addition to the data available for health risk assessment and risk communication. pubmed.ncbi.nlm.nih.gov

AI evidence extraction

Main findings

Overall cancer incidence was not increased among exposed persons (SIR 1.01, 95% CI 0.93 to 1.09). Digestive organ cancers were increased (SIR 1.23, 95% CI 1.03 to 1.46), with the highest SIR reported for gallbladder cancer (SIR 3.92, 95% CI 1.44 to 8.69). Increased testicular cancer risk among men exposed during childhood was noted but stated as likely due to confounding related to living on the lowest floors; no other significant associations were observed.

Outcomes measured

• Overall cancer incidence (all primary sites)
• Digestive organ cancers
• Gallbladder cancer
• Testicular cancer (men exposed during childhood)
• Other site-specific cancers (not specified)

Limitations

• Sample size not reported in abstract
• Exposure assessment based on apartment location relative to transformer room (no quantitative MF levels reported in abstract)
• Potential confounding noted for testicular cancer finding (associated with living on lowest floors)
• Digestive organ cancer association described as novel and requiring confirmation

Suggested hubs

• occupational-exposure (0.25)
  Published in an occupational/environmental health journal and concerns ELF magnetic-field exposure assessment, though exposure is residential rather than workplace.

{
    "study_type": "cohort",
    "exposure": {
        "band": "ELF",
        "source": "indoor transformer stations (residential)",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": "Residential exposure while living in buildings with indoor transformer stations during 1971–2016; exposure assessed by apartment location relative to transformer room"
    },
    "population": "Persons who lived in buildings with indoor transformer stations (Finland), 1971–2016",
    "sample_size": null,
    "outcomes": [
        "Overall cancer incidence (all primary sites)",
        "Digestive organ cancers",
        "Gallbladder cancer",
        "Testicular cancer (men exposed during childhood)",
        "Other site-specific cancers (not specified)"
    ],
    "main_findings": "Overall cancer incidence was not increased among exposed persons (SIR 1.01, 95% CI 0.93 to 1.09). Digestive organ cancers were increased (SIR 1.23, 95% CI 1.03 to 1.46), with the highest SIR reported for gallbladder cancer (SIR 3.92, 95% CI 1.44 to 8.69). Increased testicular cancer risk among men exposed during childhood was noted but stated as likely due to confounding related to living on the lowest floors; no other significant associations were observed.",
    "effect_direction": "mixed",
    "limitations": [
        "Sample size not reported in abstract",
        "Exposure assessment based on apartment location relative to transformer room (no quantitative MF levels reported in abstract)",
        "Potential confounding noted for testicular cancer finding (associated with living on lowest floors)",
        "Digestive organ cancer association described as novel and requiring confirmation"
    ],
    "evidence_strength": "low",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "extremely low frequency",
        "ELF",
        "magnetic fields",
        "residential exposure",
        "indoor transformer station",
        "cancer incidence",
        "SIR",
        "Finnish Cancer Registry",
        "digestive organ cancer",
        "gallbladder cancer",
        "testicular cancer"
    ],
    "suggested_hubs": [
        {
            "slug": "occupational-exposure",
            "weight": 0.25,
            "reason": "Published in an occupational/environmental health journal and concerns ELF magnetic-field exposure assessment, though exposure is residential rather than workplace."
        }
    ]
}

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