Carcinogenicity of extremely low-frequency magnetic fields: A systematic review of animal studies

Possible carcinogenicity of extremely low frequency (ELF) magnetic fields (MFs), associated with the use and transmission of electricity, has been under scientific and public debate for decades. This review aims to provide an update on studies testing carcinogenicity of ELF MFs in experimental animals. Emphasis was placed on identifying possible connections between study characteristics and the results obtained. This review followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement, and the methodological quality of the studies was evaluated using the Risk of Bias Rating Tool for Human and Animal Studies developed by the National Toxicology Program's Office of Health Assessment and Translation (OHAT). Publication bias was assessed using the caliper test. Fifty-four eligible studies were identified. Despite poor ratings in certain aspects of the risk of bias evaluation, the quality of the studies was generally relatively good, with only four studies receiving the weakest rating. Overall, there was very little evidence that ELF MFs alone are carcinogenic. Evidence of co-carcinogenicity, from studies that have used ELF MFs in combination with other agents, remains inconclusive. A clear indication of publication bias was observed, though it is unlikely that this bias alone explains all reported MF-modified effects. Based on the current literature, future studies on co-carcinogenicity of ELF MFs should employ approaches other than classical initiation-promotion models. Additionally, well-designed studies to better understand the reported effects of ELF MFs and the underlying mechanisms are warmly welcomed.