Countrywide monitoring of absorbed dose rate in air due to outdoor natural gamma radiation in India.

This article presents a comprehensive summary of long-term nationwide monitoring of outdoor natural gamma radiation in India conducted by the Indian Environmental Radiation Monitoring Network (IERMON), which uses 546 Geiger–Mueller detector-based environmental radiation monitors across 91 locations. The study found that the absorbed dose rate in air due to natural gamma radiation ranged from 50 to 808 nGy·h⁻¹, with a median value of 91 nGy·h⁻¹, and the corresponding average annual effective dose (AED) was estimated at 0.11 mSv·y⁻¹. The dose rates varied geographically, with higher levels observed in monazite-rich coastal areas of Tamil Nadu and Kerala and lower levels in western coastal states like Maharashtra and Gujarat; the data followed a log-normal distribution. These results align closely with previous studies and provide a baseline for assessing natural background radiation exposure across India.