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The activity concentration of 222Rn, 226Ra and total uranium in groundwater samples collected from wells distributed throughout the state of Chihuahua has been measured. The values obtained of total uranium activity concentration in groundwater throughout the state run from <0.03 up to 1.34 Bq l-1. Generally, radium activity concentration was <0.16 Bq l-1, with some exceptions; in spring water of San Diego de Alcalá, in contrast, the value reached approximately 5.3 Bq l-1. Radon activity concentration obtained throughout the state was from 1.0 to 39.8 Bq l-1. A linear correlation between uranium and radon dissolved in groundwater of individual wells was observed near Chihuahua City. Committed effective dose estimates for reference individuals were performed, with results as high as 134 microSv for infants in Aldama city. In Aldama and Chihuahua cities the average and many individual wells showed activity concentration values of uranium exceeding the Mexican norm of drinking water quality.

There exist potential health risks due to the presence of some elements in groundwater. This study presents measurements of gross alpha and beta activity and chemical concentrations (fluorides and nitrates) in 25 water wells in Aldama municipality, Chihuahua, Mexico. Total alpha and beta emitter analyses were performed at the Academic Unit of Nuclear Studies at the Autonomous University of Zacatecas. Radioactive elements were concentrated by total evaporation. All samples were measured with a Wallac-Oy 1411 liquid scintillate with a pulse separation option (Pulse Shape Analysis) for 6 h. Fluorine and nitrate analyses were performed at the Faculty of Engineering of the Autonomous University of Chihuahua by flow injection-hydride generation collection-atomic absorption spectrometry. Exposure levels were calculated for each well and found to exceed maximum limits allowed under Mexican law in terms of 1) gross alpha and beta activity; and 2) fluoride and nitrate concentrations. Gross alpha activity in two wells exceeded the reference value of 0.56 Bq•L −1. Fluorides and nitrates were found in 40% and 48% of water wells, respectively. Fluoride values were higher than 1.5 mg•L −1 , and the exposure doses for adults and children exceeded the reference value of 0.06 mg•kg −1 •d −1. Children are the most vulnerable, since their intake doses are near or above of 0.12 mg•kg −1 •d −1 of the minimum level of risk for the development of skeletal fluorosis or bone fractures. On the other hand, while nitrate concentrations in water wells exceeded the drinking water limit of 10 mg•L −1 , this does not represent a serious health risk, since the calculated exposure doses for adults and children are below the chronic reference level of 1.6 mg•kg −1 •d −1 established by the USEPA.

The oral administration of mineral-rich spring water is known as hydropinic treatment and is used to treat certain ailments. Health benefits are attributed to thermal spring water containing radioactive elements such as radium; this has popularized use of such radioactive water in various parts of the world, causing those who ingest it to increase their internal radiation dose. The goal of this study was to assess the activity concentrations of 226Ra present in the thermal spring waters of San Diego de Alcala, in the state of Chihuahua, Mexico, and to estimate the health risk posed to patients by the effective dose received from ingesting this water during hydropinic treatments. Water samples were taken from different areas of the San Diego de Alcala thermal springs, and pH, temperature, electrical conductivity, and total dissolved solids were measured. The 226Ra activity concentrations were measured with a liquid scintillation counter. The activity concentrations of 226Ra in sampled water varied from 125 to 452 mBq L−1 with an average of 276 ± 40 mBq L−1. The committed effective dose from each of the 226Ra activity concentrations found in samples ranged from 9.80 × 10−5 to 4.0 × 10−3 mSv for hydropinic treatments being carried out in San Diego de Alcala thermal spring spas. Different treatments had different intake rates (200, 600, 1,000, and 1,500 mL d−1) and occurred over periods of 2 or 3 wk. According to the guidelines of the US Environmental Protection Agency, the maximum permissible amount of radium in drinking water is 185 mBq L−1; the 226Ra content in most of the collected samples exceeded this limit. The committed effective doses varied with 226Ra concentration and intake rate; none exceeded the World Health Organization’s reference dose for drinking water of 0.1 mSv y−1, which is the maximum amount to which the population should be exposed.

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