International study of childhood leukemia in residences near electrical transformer rooms

Abstract

International study of childhood leukemia in residences near electrical transformer rooms Crespi CM, Sudan M, Juutilainen J, Roivainen P, Hareuveny R, Huss A, Kandel S, Karim-Kos HE, Thuróczy G, Jakab Z, Spycher BD, Flueckiger B, Vermeulen R, Vergara X, Kheifets L. International study of childhood leukemia in residences near electrical transformer rooms. Environ Res. 2024 Feb 10:118459. doi: 10.1016/j.envres.2024.118459. Abstract Objectives: New epidemiologic approaches are needed to reduce the scientific uncertainty surrounding the association between extremely low frequency magnetic fields (ELF-MF) and childhood leukemia. While most previous studies focused on power lines, the Transformer Exposure study sought to assess this association using a multi-country study of children who had lived in buildings with built-in electrical transformers. ELF-MF in apartments above built-in transformers can be 5 times higher than in other apartments in the same building. This novel study design aimed to maximize the inclusion of highly exposed children while minimising the potential for selection bias. Methods: We assessed associations between residential proximity to transformers and risk of childhood leukemia using registry based matched case-control data collected in five countries. Exposure was based on the location of the subject's apartment relative to the transformer, coded as high (above or adjacent to transformer), intermediate (same floor as apartments in high category), or unexposed (other apartments). Relative risk (RR) for childhood leukemia was estimated using conditional logistic and mixed logistic regression with a random effect for case-control set. Results: Data pooling across countries yielded 16 intermediate and 3 highly exposed cases. RRs were 1.0 (95% CI: 0.5, 1.9) for intermediate and 1.1 (95% CI: 0.3, 3.8) for high exposure in the conditional logistic model. In the mixed logistic model, RRs were 1.4 (95% CI: 0.8, 2.5) for intermediate and 1.3 (95% CI: 0.4, 4.4) for high. Data of the most influential country showed RRs of 1.1 (95% CI: 0.5, 2.4) and 1.7 (95% CI: 0.4, 7.2) for intermediate (8 cases) and high (2 cases) exposure. Discussion: Overall, evidence for an elevated risk was weak. However, small numbers and wide confidence intervals preclude strong conclusions and a risk of the magnitude observed in power line studies cannot be excluded. pubmed.ncbi.nlm.nih.gov

AI evidence extraction

Main findings

In pooled multi-country registry-based matched case-control analyses, relative risks for childhood leukemia were near null for intermediate exposure (RR 1.0, 95% CI 0.5–1.9) and high exposure (RR 1.1, 95% CI 0.3–3.8) in conditional logistic models; mixed logistic models gave RR 1.4 (95% CI 0.8–2.5) for intermediate and RR 1.3 (95% CI 0.4–4.4) for high exposure. The authors state overall evidence for elevated risk was weak, but small numbers and wide confidence intervals limit conclusions.

Outcomes measured

• Childhood leukemia risk

Limitations

• Very small numbers of exposed cases (pooled: 16 intermediate and 3 high)
• Wide confidence intervals
• Exposure classification based on apartment location relative to transformer rather than direct measurements for individuals
• Results influenced by data from the most influential country (country not specified in abstract)

Suggested hubs

• occupational-exposure (0.05)
  Study is residential rather than occupational; included only as a weak match due to transformer-related exposure context.

{
    "study_type": "case_control",
    "exposure": {
        "band": "ELF",
        "source": "residential proximity to built-in electrical transformers (transformer rooms)",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": null
    },
    "population": "Children (childhood leukemia cases and matched controls) in five countries; residences in buildings with built-in electrical transformers",
    "sample_size": null,
    "outcomes": [
        "Childhood leukemia risk"
    ],
    "main_findings": "In pooled multi-country registry-based matched case-control analyses, relative risks for childhood leukemia were near null for intermediate exposure (RR 1.0, 95% CI 0.5–1.9) and high exposure (RR 1.1, 95% CI 0.3–3.8) in conditional logistic models; mixed logistic models gave RR 1.4 (95% CI 0.8–2.5) for intermediate and RR 1.3 (95% CI 0.4–4.4) for high exposure. The authors state overall evidence for elevated risk was weak, but small numbers and wide confidence intervals limit conclusions.",
    "effect_direction": "unclear",
    "limitations": [
        "Very small numbers of exposed cases (pooled: 16 intermediate and 3 high)",
        "Wide confidence intervals",
        "Exposure classification based on apartment location relative to transformer rather than direct measurements for individuals",
        "Results influenced by data from the most influential country (country not specified in abstract)"
    ],
    "evidence_strength": "low",
    "confidence": 0.85999999999999998667732370449812151491641998291015625,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "childhood leukemia",
        "extremely low frequency magnetic fields",
        "ELF-MF",
        "residential exposure",
        "transformer rooms",
        "built-in electrical transformers",
        "registry-based",
        "matched case-control",
        "multi-country"
    ],
    "suggested_hubs": [
        {
            "slug": "occupational-exposure",
            "weight": 0.05000000000000000277555756156289135105907917022705078125,
            "reason": "Study is residential rather than occupational; included only as a weak match due to transformer-related exposure context."
        }
    ]
}

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