NANOSIEVERTS (nSv): Extremely Low Radiation Doses and Their Biological Significance A Scientific Review of Radiation Measurement, Environmental Exposure, Biological Effects, and Radiation Protection

This scientific review examines extremely low radiation doses expressed in nanosieverts (nSv), focusing on their physical measurement, dosimetric interpretation, environmental distribution, and potential biological significance. It provides an overview of natural background radiation, low-dose exposure pathways, radiation measurement techniques, measurement uncertainty, cellular responses, and radiation-protection principles. The publication critically discusses the distinction between absorbed dose, equivalent dose, effective dose, and dose rate, as well as the application and limitations of the Linear No-Threshold (LNT) model in low-dose radiation-risk assessment. It also examines international radiation-protection recommendations and the interpretation of nanosievert-scale measurements in environmental and public-health contexts. The review aims to provide a scientifically grounded reference for researchers, radiation-protection professionals, students, and readers interested in radiation dosimetry, radiobiology, environmental monitoring, and nuclear safety.