Thoron and radon measurements in Romanian schools.

A new thoron/radon survey was started in the north-western part of Romania, covering three counties, using discriminative detectors (RADUET). All detectors were deployed throughout 3 months, covering the spring period. The measured radon and thoron concentration ranged from 31 to 414 Bq m(-3) and from below the detection limit to 235 Bq m(-3), respectively. In this survey, 35 schools were submitted to investigation; 21 of the schools included in this study presented radon concentrations higher than 100 Bq m(-3), the reference level recommended by the World Health Organization in 2009. The seasonal effective dose calculated from these exposures, overlapping all three counties, ranged between 0.32 and 0.54 mSv.