7.4 EVIDENCE FOR HEALTH EFFECTS
Modern RF safety recommendations draw on laboratory experiments, animal studies, controlled human investigations, epidemiological studies, dosimetry, and computational and thermal modeling. Each line of evidence answers different questions and has different strengths and limitations.
No individual study is decisive. Expert reviews consider exposure characterization, study design, sample size, control of bias and confounding, statistical analysis, reproducibility, biological plausibility, and consistency across independent studies and research methods. Greater weight is placed on findings that remain credible across these tests.
This process supports electrical stimulation and excessive tissue heating as the established adverse effects of RF exposure. Many other outcomes have been investigated, including cancer, reproductive and neurological effects, symptoms, immune-system changes, and proposed non-thermal mechanisms. Individual studies have sometimes reported associations or biological responses, but evidence is not treated as established unless the overall body of research supports a causal adverse effect.
In 2011, the International Agency for Research on Cancer (IARC) classified RF electromagnetic fields as Group 2B, possibly carcinogenic to humans, on the basis of limited evidence. This is a hazard classification: it identifies whether an agent might be capable of causing cancer under some circumstances. It does not quantify the risk from a particular source or demonstrate that exposures below current restrictions cause cancer.
More recent systematic reviews, including reviews commissioned to inform the WHO’s RF health assessment, have generally not found convincing evidence of increased risk for the principal human health outcomes examined at ordinary exposure levels. The certainty of the evidence varies among outcomes, however, and limitations in exposure assessment, rapidly changing technologies, and sparse evidence for some exposure circumstances justify continuing research.
Scientific conclusions should therefore be expressed neither as proof that every reported effect is harmful nor as proof that no uncertainty remains. The appropriate approach is to describe what has been established, identify remaining uncertainties, and revise guidance when the weight of credible evidence changes.