Power-Frequency Fields at Work: New Systematic Review Probes Hidden Heart Risks

Millions of workers around the world spend their entire careers within arm’s reach of the invisible infrastructure of modern civilization: high-voltage transmission lines, transformers, electric railways, welding stations, and power stations humming at 50 or 60 hertz. Whether these ever-present extremely low-frequency (ELF) electromagnetic fields can damage the human heart has remained one of occupational health’s most stubborn open questions. Now a new systematic review, published in Public Health Reviews by a team from Shahrekord University of Medical Sciences in Iran, has sifted the global evidence and reached a conclusion that is as unsettling as it is cautious: half of the eligible studies report a link between workplace ELF exposure and cardiovascular outcomes, but the evidence is still too inconsistent to declare a cause.

The review, registered prospectively with PROSPERO under identifier CRD420251078768 and conducted according to PRISMA guidelines, was no small undertaking. The researchers searched six major bibliographic databases—Scopus, PubMed, Web of Science, Embase, MEDLINE, and Google Scholar—capturing records up to August 19, 2026. From an initial haul of 5,077 articles, they whittled the field down to just 14 studies that met their strict criteria: participants had to be workers exposed to ELF fields in occupational settings, exposure had to be assessed with an objective or clearly described method, and each study had to report at least one cardiovascular outcome. Two reviewers screened independently, resolving disagreements by consensus, and achieved remarkably high agreement, with Cohen’s kappa coefficients of 0.91 in the title-and-abstract phase and 0.94 in the data-extraction phase.

The 14 studies that survived the cull collectively covered 49,709 participants across 13 countries, from Sweden and the Netherlands to China, Japan, South Korea, Iran, Australia, and Romania. Five were cohort studies, four were case-control studies, four were controlled laboratory experiments, and one was cross-sectional. The populations ranged from electrical utility workers and railway engineers to powerplant technicians, high-voltage linesmen, automotive workers, and petrochemical staff. Exposure frequencies spanned 0.01 to below 300 hertz, and measured field strengths ranged from less than 0.1 to a striking 280 microtesla—well below the internationally accepted occupational limit of 1,000 microtesla for 50–60 hertz fields, but vastly above typical residential levels. Exposure duration in the occupational studies stretched from five days to 31 years.

The headline result is a perfect split: seven of the 14 studies found a statistically significant association between ELF exposure and some cardiovascular outcome, while seven found none. The positive findings were diverse. In Romania, Danulescu and colleagues reported odds ratios of around 5.2 to 5.4 for cardiovascular alterations—including arrhythmias, conduction disturbances, and myocardial ischemia—among electric train drivers and high-voltage linesmen. A South Korean case-control study linked elevated ELF exposure to changes in systolic blood pressure, and a Chinese study of automotive workers suggested effects on the nervous, cardiovascular, and hematological systems. In the powerplant cross-sectional study from Iran, exposed workers showed significantly higher levels of inflammatory markers and blood cell counts, including interleukin-1 beta, interleukin-6, white blood cells, and platelets.

The cohort studies, which carry the greatest weight for establishing long-term risk, told a more fragmented story. A Swedish cohort of nearly 28,000 workers found a slight increase in acute myocardial infarction risk in the highest exposure category, with a suggestive exposure-response relationship, but no association with arrhythmia deaths, other ischemic heart disease, or atherosclerosis. Russian railroad data analyzed by Ptitsyna and colleagues pointed to increased coronary heart disease among electric locomotive drivers exposed to fields of 50 to 280 microtesla. Yet the large Dutch cohort of more than 120,000 electrical utility workers found essentially no link to cardiovascular mortality (hazard ratio 1.02), and Swiss railway workers exposed to intermittent 16.7-hertz fields and French electricity transmission workers showed no elevated cardiovascular death rates either.

Why do credible studies disagree so sharply? The review authors point to plausible biology on one side and methodological noise on the other. According to Faraday’s law, time-varying magnetic fields induce electric currents in the body. At sufficient intensity these currents can directly excite electrically active cells—neurons and muscle fibers—and even at lower intensities they may perturb electrochemical processes: ion transport across cell membranes, voltage-gated channel behavior, membrane protein function, and hormone binding at the cell surface. Because normal cardiac rhythm depends on precisely coordinated electrical activity, such perturbations could in principle alter heart rate, heart rate variability, and blood pressure. Supporting this, previous double-blind research has observed reduced heart rate variability during short-term ELF exposure, and clinical studies have reported electromagnetic-field-related vasodilation and improved microcirculation.

Yet a possible mechanism is not proof of harm, and the review identifies several reasons why real-world signals may be masked or exaggerated. Most cohort studies relied on job-exposure matrices and mortality databases rather than personal dosimetry, an approach that produces nondifferential misclassification of both exposure and outcome—an error that typically biases risk estimates toward unity, hiding true effects. Conversely, case-control studies, which more often reported positive findings, are vulnerable to differences between exposed and comparison groups and to incompletely controlled confounders such as noise, air pollution, physical workload, smoking, and psychosocial stress. The experimental studies added another wrinkle: three of four found no acute cardiovascular effects even at intensities far exceeding occupational levels, suggesting that brief exposure may be insufficient and that effects, if real, may accumulate over years of repeated exposure.

The pattern that emerges from the synthesis is that of a mild-to-moderate signal rather than a dramatic one. No study in the review found a significant effect on atherosclerosis or overall cardiovascular mortality, the endpoints of greatest clinical gravity. Significant associations clustered around physiological and subclinical measures: blood pressure shifts, altered electrocardiographic signals, arrhythmias, conduction abnormalities, hematological and inflammatory changes, and in some analyses, myocardial infarction and coronary heart disease. The authors argue that exposure level, duration, and frequency all matter—non-significant studies tended to involve fields below roughly 8 microtesla—though even high-exposure studies sometimes found nothing, underscoring the role of study design, small samples, and outcome definitions.

For occupational health practitioners, the practical takeaway is measured. The review does not support changing existing exposure limits, which stand at 1,000 microtesla for workers and 200 microtesla for the public at power frequencies. Instead, the authors recommend staying within current standards while paying special attention to high-exposure environments: regular exposure assessments, identification of major sources, proper maintenance of electrical equipment, and engineering and administrative controls that reduce unnecessary exposure. Because electrical systems are so ubiquitous, they note, even a small increase in cardiovascular risk—if eventually confirmed—could matter at the population level, particularly for workers with decades-long exposure or coexisting risk factors. ELF fields should be viewed as a possible additional occupational factor, not a proven major cause, alongside far better-established culprits like noise, pollution, and stress.

The review’s limitations are candidly acknowledged. Indirect exposure assessment in cohorts, short exposure durations in lab studies, incomplete control of confounders, and the absence of any study on residential exposure all constrain the conclusions. The single cross-sectional study cannot establish whether exposure preceded the biological changes it detected, and no study distinguished effects in healthy people from those in patients with existing cardiovascular disease. What the review delivers instead is a rigorous map of where the evidence stands: a genuine 50-50 split among qualifying studies, credible biological plausibility, and a clear agenda for future research. Investigators now need longitudinal studies with personal exposure measurement, exposure-response modeling, and careful adjustment for the occupational and personal factors that confound today’s literature. Until then, the hum of the power grid remains a suspect that science has not yet cleared—or convicted.

Subject of Research: Occupational exposure to extremely low-frequency electromagnetic fields and cardiovascular health outcomes

Article Title: Occupational exposure to extremely low-frequency fields and cardiovascular consequences: a systematic review

Article References: Raeisi, E., Maghare Dehkordi, S., Yazdanirad, S., & Mohammadian-Hafshejani, A. (2026). Occupational exposure to extremely low-frequency fields and cardiovascular consequences: a systematic review. Public Health Reviews, 47, Article 1609952. https://doi.org/10.3389/phrs.2026.1609952

Image Credits: AI Generated

DOI: 10.3389/phrs.2026.1609952

Keywords: extremely low-frequency fields, electromagnetic fields, occupational health, cardiovascular disease, systematic review, myocardial infarction, arrhythmia, blood pressure, heart rate variability, exposure assessment, public health, worker safety