Soil gas radon, indoor radon and its diurnal variation in the northern region of Cameroon

Soil gas radon and indoor radon measurements have been carried out in Mayo-Louti and Benoue Divisions in northern Cameroon. Concentrations of radon in soil have been measured using Markus 10 at the depth of about 1 m. Radon concentration in soil varies from 0.9 to 13.8 kBq m(-3) with a mean value of 4.6 kBq m(-3). Average daily indoor radon concentrations measured with RadonEye+(2) detectors vary from 7 to 60 Bq m(-3) with an average of 17 Bq m(-3). Indoor radon concentrations measured with passive RADTRAK detectors range between 15 and 104 Bq m(-3) with a geometric value of 38 Bq m(-3) and a geometric standard deviation of 1.5. This geometric value is lower than the value of 30 Bq m(-3) given by UNSCEAR. Indoor radon inhalation dose ranges between 0.28 and 1.97 mSv a(-1) with geometric value of 0.72 mSv a(-1) (at 0.03 standard deviation). Outdoor radon inhalation ranges between 0.02 and 0.26 mSv a(-1) with a mean value of 0.09 mSv a(-1). The total annual effective dose due to indoor and outdoor radon exposure for this study area is 0.81 mSv a(-1), less than 1.15 mSv a(-1) the world average value given by UNSCEAR. There is no significant radiological risk for the inhabitants.