Uranium-238 and thorium-232 series concentrations in soil, radon-222 indoor and drinking water concentrations and dose assessment in the city of Aldama, Chihuahua, Mexico.

High-resolution gamma spectrometry was used to determine the concentration of 40K, 238U and 232Th series in soil samples taken from areas surrounding the city of Aldama, in Chihuahua. Results of indoor air short-time sampling, with diffusion barrier charcoal detectors, revealed relatively high indoor radon levels, ranging from 29 to 422 Bq/m3; the radon concentrations detected exceeded 148 Bq/m3 in 76% of the homes tested. Additionally, liquid scintillation counting showed concentrations of radon in drinking water ranging from 4.3 to 42 kBq/m3. The high activity of 238U in soil found in some places may be a result of the uranium milling process performed 20 years ago in the area. High radon concentrations indoor and in water may be explained by assuming the presence of uranium-bearing rocks underneath of the city, similar to a felsic dike located near Aldama. The estimated annual effective dose of gamma radiation from the soil and radon inhalation was 3.83 mSv.

Radioactivity in bottled waters sold in Mexico.

Measurements of gross alpha and beta activities were made on 21 domestic and international brands of bottled (purified and mineral) water sold in the Mexican market to assess its radiological quality. Alpha and beta activities were determined using a liquid-scintillation detector with pulse-shape analysis feature. All the purified water had values of beta activity lower than the limit for potable drinking water (1.0 Bq/l), while three brands surpassed the limit of alpha activity (0.1 Bq/l). The limit for alpha radioactivity content was exceed by three mineral waters; the results show a correlation between radioactivity content and mineral salts, which are related with the origin and treatment of the waters.