External dose measurements in the Eloor industrial area in the Ernakulam district of Kerala, India

Natural background radiation of a particular region is one of the distinctive factors defining the status of environment. Eloor Island is an industrial area in Ernakulum District of the state of Kerala, India. The indoor and outdoor gamma level measurements have been carried out for the region for evaluating the annual effective dose to the population residing in this area.
Measurements of indoor gamma dose were done for a whole year using Thermo Luminescent Dosimeters (TLDs) and GM tube based survey meters in forty five selected locations. The activity concentration of 232Th, 238U and 40K in the samples were analyzed using gamma spectrometry. The outdoor external gamma ray dose rates were evaluated from the activity concentration of 40K, 238U and 232Th in the soil samples collected from the study area.
The average indoor gamma dose measured using TLDs were found to be 1219 µGy y-1. The measured activity in the soil samples had range from 92.5 Bq kg-1 to 792.8 Bq kg-1 for 232Th, 9.2 Bq kg-1 to 114.6 Bq kg-1 for 238U and 265.9 Bq kg-1 to 851.9 Bq kg-1 for 40K. From the observed mean dose levels, the annual effective dose equivalent to population residing in the island has been estimated and is found to be 0.68 mSv y-1 for indoors and 0.32 mSv y-1 for outdoors.
The annual effective dose equivalent to population estimated for indoor is found to be higher as compared to the global average the same for outdoor was found to be less when compared with the natural background gamma level reported by UNSCEAR for normal background areas.