Users of mobile telephones are exposed to radiofrequency radiation. On
e of the questions still open today is whether amplitude-modulated rad
iofrequency signals from digital phones exert specific bioeffects diff
erent from those of continuous (unmodulated) radiofrequency radiation.
This paper reviews recent literature on the bioeffects of amplitude-m
odulated radiofrequency radiation, from cells to humans. The consisten
cy of the results is discussed and exposure parameters are compared to
identify possible biologically active forms of amplitude modulation.
Several studies have reported findings consistent with effects on the
nervous system and cancer-related biological processes. However, the m
ethods and exposure parameters vary widely, and no independent replica
tions of the positive findings have been reported. The results availab
le today fail to support the existence of well-defined modulation-spec
ific bioeffects from exposure to radiofrequency radiation. Additional
systematic studies are needed to identify possible reproducible modula
tion-dependent effects and biologically active modulation parameters.