Continuous monitoring of outdoor natural gamma absorbed dose rate in air: a long-term study in Kolkata, West Bengal, India

This study contributes to the overarching Indian Environmental Radiation Monitoring Network initiative, concentrating on the continual assessment of the gamma absorbed dose rate in outdoor air attributable to natural gamma radiation in Kolkata, West Bengal, India. Over a span of fourteen years (2011-2024), data were gathered from 32 monitoring sites within the city utilizing permanently installed Geiger-Mueller detector-based environmental radiation monitors. This paper offers an analysis of extensive findings from long-term monitoring efforts. The absorbed gamma dose rate in outdoor air varied among the monitoring sites, ranging from 78 +/- 5 to 137 +/- 4 nGy h- 1, with a mean value of 107 +/- 12 nGy h- 1. The estimated mean annual effective dose due to outdoor natural gamma radiation ranged from 0.10 +/- 0.01 to 0.17 +/- 0.01 mSv y- 1, with an overall mean of 0.13 +/- 0.01 mSv y-1.