Occupational exposure to electromagnetic fields in relation to leukemia and brain tumors: a case-control study in Sweden.

Abstract

Occupational exposure to low-frequency electromagnetic fields (EMF) was studied in 250 leukemia patients and 261 brain-tumor cases, diagnosed in 1983-87 and compared with a control group of 1,121 randomly selected men, from the mid-region of Sweden, 1983-87. We based the exposure assessment on measurements from 1,015 different workplaces. On the basis of the job held longest during the 10-year period before diagnosis, we found an association between the average, daily, mean level of EMF and chronic lymphocytic leukemia (CLL). The risk increased with increasing level of exposure. The odds ratios (OR) and the 95 percent confidence interval (CI) for three consecutive levels of exposure were: 1.1 (CI = 0.5-2.3); 2.2 (CI = 1.1-4.3); 3.0 (CI = 1.6-5.8), respectively. No association was observed for acute myeloid leukemia (OR = 1.0, CI = 0.5-1.8; OR = 0.8, CI = 0.4-1.6; OR = 1.0, CI = 0.6-1.9). For brain tumors, the corresponding risk estimates were 1.0 (CI = 0.7-1.6); 1.5 (CI = 1.0-2.2); 1.4 (CI = 0.9-2.1). Different EMF indices were tested. Tasks with frequent or large variations between high and low field-densities (high standard deviation) were more common among CLL subjects. For brain tumors, a prolonged high level (high median values) showed the strongest association. Confounding by place of residence, smoking, benzene, ionizing radiation, pesticides, and solvents was evaluated, and these factors did not seem to have a decisive influence on the associations. We also analyzed other potential sources of bias. For CLL, there were indications of an excess number of low-exposure subjects among non-responders, which, to some extent, may have enhanced but not caused the risk estimates obtained. Our conclusion is that the study supports the hypothesis that occupational EMF exposure is a hazard in the development of certain cancers.

AI evidence extraction

Main findings

Using workplace measurements (1,015 workplaces) and the job held longest in the 10 years before diagnosis, higher average daily mean EMF exposure was associated with increased odds of chronic lymphocytic leukemia (dose-response across three exposure levels: OR 1.1, 2.2, 3.0). No association was observed for acute myeloid leukemia across exposure levels. For brain tumors, risk estimates were 1.0, 1.5, and 1.4 across exposure levels, with the strongest association reported for prolonged high levels (high median values).

Outcomes measured

• Leukemia (including chronic lymphocytic leukemia and acute myeloid leukemia)
• Brain tumors

Limitations

• Potential non-response bias noted: excess low-exposure subjects among non-responders for CLL may have enhanced risk estimates
• Exposure classification based on the job held longest in the 10-year period before diagnosis (may not capture full occupational history)
• Frequency, SAR, and specific exposure metrics/units not reported in the abstract

Suggested hubs

• occupational-exposure (0.95)
  Study evaluates occupational low-frequency EMF exposure using workplace measurements in relation to cancer outcomes.

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    "study_type": "case_control",
    "exposure": {
        "band": "ELF",
        "source": "occupational",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": "Job held longest during the 10-year period before diagnosis; cases diagnosed 1983–87"
    },
    "population": "Men from the mid-region of Sweden (1983–87)",
    "sample_size": 1632,
    "outcomes": [
        "Leukemia (including chronic lymphocytic leukemia and acute myeloid leukemia)",
        "Brain tumors"
    ],
    "main_findings": "Using workplace measurements (1,015 workplaces) and the job held longest in the 10 years before diagnosis, higher average daily mean EMF exposure was associated with increased odds of chronic lymphocytic leukemia (dose-response across three exposure levels: OR 1.1, 2.2, 3.0). No association was observed for acute myeloid leukemia across exposure levels. For brain tumors, risk estimates were 1.0, 1.5, and 1.4 across exposure levels, with the strongest association reported for prolonged high levels (high median values).",
    "effect_direction": "mixed",
    "limitations": [
        "Potential non-response bias noted: excess low-exposure subjects among non-responders for CLL may have enhanced risk estimates",
        "Exposure classification based on the job held longest in the 10-year period before diagnosis (may not capture full occupational history)",
        "Frequency, SAR, and specific exposure metrics/units not reported in the abstract"
    ],
    "evidence_strength": "low",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "occupational exposure",
        "low-frequency electromagnetic fields",
        "ELF EMF",
        "case-control",
        "Sweden",
        "chronic lymphocytic leukemia",
        "acute myeloid leukemia",
        "brain tumors",
        "workplace measurements",
        "dose-response"
    ],
    "suggested_hubs": [
        {
            "slug": "occupational-exposure",
            "weight": 0.9499999999999999555910790149937383830547332763671875,
            "reason": "Study evaluates occupational low-frequency EMF exposure using workplace measurements in relation to cancer outcomes."
        }
    ]
}

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