SUMMARY
The Radiation in thermal springs used in recreational areas may represent a public health problem. The objective of this study was to quantify the radon (222Rn) level in air and to measure the total radiation intensity in a natural thermal pool located in San Diego de Alcala, Chihuahua, Mexico. A thermal spring was selected and the door and window were closed to simulate the bathing pool used for the public. The 222Rn level in air was detected using an AlphaGUARD (Professional Radon Monitor) from GENITRON brand. This parameter was quantified in Bq m-3 at different times 10, 20, 30, 40, 50 and 60 min, three measurements were made; the first in the 2014 winter season (January) and two in the time of spring 2015 (May and June) analysis was by regressing for each measurement. Average annual effective dose (DPA) inhalation of radon to which are exposed those who come to the hot springs depending on the number of visits and length of stay was estimated, the range varied from 0.0005±4x10-4 mSv when the baths are visited 12 time a year with a stay of 10 min until 0.0352±1.1x10-2 mSv visiting once a week for a period 60 min