We propose a biologically based measure of EMF radiation to replace the energy-based "specific absorption rate" (SAR). A wide range of EMF frequencies has been linked to an increased risk of cancer. The SAR value used to measure the EMF dose and set the safety standard in the radiofrequency (RF) range fails as a standard for predicting cancer risk in the ELF power frequency range. Because cancers are believed to arise from mutations in DNA, changes in DNA induced by interaction with EMF could be a better measure of the biologically effective dose in both frequency ranges. The changes can be measured by transcriptional alterations and/or translational changes in specific proteins. Because ionizing radiation also causes DNA damage, a biologically based standard related to stimulation of DNA could apply over a much wider range of the electromagnetic spectrum. A safety standard for exposure to a wide range of non ionizing frequencies can be based on the documented changes in DNA biochemistry that arise from interactions with EMF.