Environmental radioactivity studies in Kabul and northern Afghanistan

From earlier surveys conducted by soviet researchers, the Kabul area was identified as a region of high natural radioactivity. In addition, depleted uranium ammunition was used by the Soviet armed forces. Fragmentary maps (often only given in relative units) indicate regions of anomalously elevated gamma radiation dose rates. In recent years, residential houses have been built in some of these places. However, no detailed information of uranium and thorium distributions in the upper soil and rock exists. In order to assess possible radiological risk, soil and rock samples as well as all-purpose water samples were collected and measured with regard to radioisotope content and contamination by other pollutants such as, e.g., heavy metals. Activity concentrations in soil and rocks ranged between 160 to 28,600 Bq/kg, 73 to 383,000 Bq/kg, and 270 to 24,600 Bq/kg for uranium, thorium, and potassium, respectively. The elevated thorium abundances was traced back to incorporation into cheralite minerals. No anomalies of the radioactive equilibria were found in the decay chains. Hence, contributions of depleted uranium or other anthropogenic sources can be excluded. However, the high uranium content causes enhanced radon levels in houses and dwellings up to mean activity concentrations of 2000 Bq/m³ strongly exceeding the reference level of 300 Bq/m³ recommended by the ICRP. Heavy metal concentrations of some of the investigated waters also exceed the regulatory limits and are not safe for drinking. Dose assessments are given.