What is the specific absorption rate (SAR)?

The specific absorption rate (SAR) is defined as the mass normalized rate of energy absorption, which measures how much electromagnetic energy is absorbed by a unit mass of human tissue when exposed to radiofrequency fields. It is commonly expressed in watts per kilogram (W/kg). SAR is particularly relevant in evaluating the potential health impacts of exposure to radiofrequency radiation, such as that from mobile phones and other wireless devices. The normalization to mass allows for comparison between different body types, since absorption can vary significantly based on the individual's size and mass.

While other concepts like energy absorption per square meter or the rate of temperature increase are related to the effects of electromagnetic fields, they do not accurately capture the mass-specific nature of SAR as it pertains to health and exposure assessments. Intensity of radiation exposure over time would typically refer to power density or exposure limits, which are distinct from the SAR measurement focused on energy absorbed by body mass. Thus, understanding SAR is crucial for assessing the safety and guidelines around exposure to electromagnetic fields.