Determination of the internal dose due to the intake of 226Ra and 210Pb in drinking water from deep wells in the Metropolitan Region of Recife-Brazil

The Metropolitan Region of Recife, the capital of the state of Pernambuco in northeastern Brazil, has a high demographic density and developed under a region of marine phosphorus with high concentrations of phosphate that naturally contains uranium ore, producing ionizing radiation from descendants of the radioisotope ²³⁸U where ²²⁶Ra and ²¹⁰Pb are of great importance in verifying the probable harmful effects on human health due to environmental radioactivity. The supply of drinking water is the responsibility of the state-owned company COMPESA which uses wells of great depth to complete the supply of drinking water for the entire population. COMPESA and the RAE Group of the Federal University of Pernambuco developed a joint project to assess the concentrations of ²²⁶Ra and ²¹⁰Pb and estimate the equivalent and effective doses caused by ingesting these radiation sources. According to the above, this research aimed to evaluate concentrations of ²²⁶Ra and ²¹⁰Pb in drinking water samples from 110 deep wells in Recife. The activities of ²²⁶Ra and ²¹⁰Pb ranged from 1.4 ± 0.3 to 119.3 ± 12.9 and from 25.6 ± 3.3 to 563.2 ± 45.6 mBq.L^-1, with arithmetic means of 48.1 ± 3.8 and 231.1 ± 20 mBq.L^-1, respectively. The equivalent doses average in bone tissue due to ²²⁶Ra and ²¹⁰Pb were 0.45 ± 0.04 and 3.9 ± 0.37 mSv.y^-1, and the annual average effective doses were 0.01 ± 0.00 and 0.13 ± 0.01 mSv.y^-1, respectively.

Risk survey for the population of Recife and neighboring cities due to the occurrence of radium in groundwater

The Metropolitan Region of Recife and its surroundings are heavily exploited to capture water for public supply through tubular wells. However, a survey of the levels of natural radionuclides from these sources had never been carried out, even though part of this region contains a phosphate deposit that has a high concentration of natural uranium. In this context, this research aimed to identify ²²⁸Ra and ²²⁶Ra levels in groundwater in the coastal region of Pernambuco, Brazil. About 110 points (wells) of drinking water for public supply were identified and studies were carried out to estimate the level of ingestion and subsequent risk due to the presence of this radionuclide. The average concentration of combined radium was 104 mBq.L^-1. For ²²⁸Ra an effective dose of 0.46, 0.11, 0.12 and 0.0276 mSv.y^-1 for infants, children aged 1 and 10 and adults, respectively, were obtained. Although doses above those recommended by WHO were found, the equivalent dose and the induction of bone sarcoma did not indicate a risk to the population. Groundwater with higher dose values is influenced by local geology.

MONITORING AND CHARACTERISATION OF NEW EVIDENCE OF NATURAL RADIONUCLIDES IN ROCK OUTCROPS IN PARAÍBA-BRAZIL

The radiometric monitoring carried out in the present study allowed the discovery of anomalous granite outcrops in natural radionuclides in the rural area of São Mamede in the state of Paraíba, Brazil. The characterisation study made it possible to determine maximum specific concentrations of approximately 199 kBq kg-1 of 238U, 85 kBq kg-1 of 226Ra, 26 kBq kg-1 of 232Th and 24 kBq kg-1 of 40K. Models for environmental dosimetry were applied, which resulted in obtaining the following quantities: radium equivalent (Raeq), indices of external (Hex), internal (Hin) and representative (Iyr) damage, and the effective outdoor dose (HE). The maximum results presented were approximately 123 kBq kg-1, 332, 562, 832, and 68 mSv y-1, respectively. Consequently, it was possible to define the region as of high radioactive background due to isolated rocky outcrops located in the rural area of the mentioned municipality.

RADIOACTIVE DISEQUILIBRIUM AND DYNAMIC OF NATURAL RADIONUCLIDES IN SOILS IN THE STATE OF PERNAMBUCO-BRAZIL

Environmental radioactivity studies have been allowed establishing radiometric patterns in several area of the earth's crust. The work was conducted through radiometric analyses of regions with high levels of radionuclides and others with no history of anomalies. The research allowed establishing the radiometric profile of soils in the state of Pernambuco, Brazil, using a gamma spectrometry system. The specific activities ranged from 16.5 to 287.5 Bq kg-1 for 238U, 2.0 to 191.7 Bq kg-1 for 226Ra, 1.3 to 281.4 Bq kg-1 for 232Th and from 5.0 to 2600.9 Bq kg-1 for 40K. The results showed areas with low levels of ionizing radiation. However, for 40K some points presented high values, although non-representative of the number of samples investigated. The 226Ra/238U and 232Th/238U ratios allowed to determine the radioactive imbalance condition and to obtain information about aspects of soil availability providing an assessment of the dynamics of these radionuclides.

ENVIRONMENTAL IONIZING RADIATION DOSE OUTDOOR IN AN INHABITED AREA WITH A HIGH CONCENTRATION OF URANO-PHOSPHATE IN NORTHEAST OF BRAZIL

A marine phosphorus region with high concentrations of phosphate, coastwise of Pernambuco, Northeast of Brazil, is densely inhabited. Rock phosphate deposits naturally contain uranium ore that produces ionizing radiation from it and its natural descendants, furthermore, its thorium and potassium concentrations are comparable to those usually found in soils. Radiological monitoring of this environment is important to verify the occurrence of harmful effective doses for the adjacent population. This study aimed at the in situ radiometric monitoring in four cities of the north of the Metropolitan Region of Recife-Pernambuco, estimating the effective environmental dose to which the local population is subject. In total, 91 points were monitored with a discriminator-type detector. The outdoor environmental effective dose rates ranged from 1.99 ± 0.09 to 7.59 ± 0.36 mSv y-1, with an average of 2.60 ± 0.69 mSv y-1.

Natural radionuclides in electronic waste: an initial approach

Some radionuclides are present in trace amount in the raw material of electronic devices that suffer obsolescence and are improperly disposed of. Obsolete personal computers become electronic waste and may contain potential environmental contaminants. Furthermore, there may be an additional concern: the ionizing radiation emission. This study aimed to assess qualitatively the possibility of alpha and beta particles and gamma rays reaching somehow workers involved in the handling of such wastes. Using gamma spectrometry method, we analyzed a set of 10 microprocessors randomly taken from motherboards incorrectly discarded. The analysis resulted in the occurrence of primordial radioisotopes in the microchips.

THERMOLUMINESCENT DOSIMETRY IN THE EVALUATION OF NATURAL RADIOACTIVITY INDOOR OF HOMES NEAR THE URANIUM DEPOSIT OF PARAÍBA, BRAZIL

High levels of primordial radionuclides have been reported in soils and rocks of São José de Espinharas, in the state of Paraiba, Brazil. These radionuclides are derived from high concentrations of natural uranium and thorium from a mine in the region. Thus, there is a need for a dosimetric evaluation in the area near the mine and the surrounding cities. In this study, the annual effective dose was analyzed in 178 points of five cities. The measurements were performed using thermoluminescent dosimetry with LiF:Mg, Ti (TLD-100). The annual effective dose from environmental exposure varied from 0.71 to 2.07 mSv, with an arithmetic mean of 0.99 mSv. This average is more than twice the estimated value for indoor environments adopted by the UNSCEAR, which is 0.41 mSv. These results will allow establishing reference values for background radiation of the region and criteria to infer a stochastic risk for the local population.