Environmental dose rate assessment from an active fault zone in Western Anatolia, Turkey: towards retrospective epidemiology

Abstract

In this study we present data regarding natural radioactivity from a populated active tectonic area based on site measurements using a field gamma spectrometer. The results will provide data to the scientists for dating studies as well as epidemiological studies towards ancient human life, also termed as retrospective epidemiology. The study area covers an active tectonic region in western Anatolia surveyed using on-site gamma spectrometer. More than 500 sites were measured across the region on a 150- km grid. Radiation background shows relatively non-homogenous level of radiation in the area. The gamma dose rate measured in Gediz graben was found in the range between 0.8120- 1.7540 mGya–1 (94-203 nGyh–1) with an average value of 1.2292 mGy/a (142 nGyh–1), whereas it was in the range between 0.5530-1.1491 mGy/a (64-133 nGyh–1) with an average value of 0.8397 mGy/a (97 nGyh–1) across Buyuk Menderes graben. The relative contribution of 238U decay chain to gamma dose rate is between 0.2002- 0.4630 mGya–1, of 232Th decay series is 0.3089- 0.8136 mGya–1, and of 40K is 0.1270- 0.3468 mGya–1 in the whole studied area. The average annual effective dose equivalents from the calculated outdoor terrestrial gamma radiation was between 90-215 μSva–1, above world average of 70 μSv per year, and the measured outdoor dose rate (terrestrial plus cosmic) on the ground was between 133-257 μSva–1. The significance of all these numbers is discussed in the framework of epidemiological studies, in order to correlate these enhanced dose rate values directly to specific diseases such as cancer.