Environmental radon studies in Mexico.

Radon has been determined in soil, groundwater, and air in Mexico, both indoors and outdoors, as part of geophysical studies and to estimate effective doses as a result of radon exposure. Detection of radon has mainly been performed with solid-state nuclear track detectors (SSNTD) and, occasionally, with active detection devices based on silicon detectors or ionization chambers. The liquid scintillation technique, also, has been used for determination of radon in groundwater. The adjusted geometric mean indoor radon concentration (74 Bq m-3) in urban developments, for example Mexico City, is higher than the worldwide median concentration of radon in dwellings. In some regions, particularly hilly regions of Mexico where air pollution is high, radon concentrations are higher than action levels and the effective dose for the general population has increased. Higher soil radon levels have been found in the uranium mining areas in the northern part of the country. Groundwater radon levels are, in general, low. Soil-air radon contributing to indoor atmospheres and air pollution is the main source of increased exposure of the population.