Environmental radioactivity measurements and applications – Difficulties, current status and future trends

The status of natural radioactivity in Nigerian environments

Proper documentation of baseline radiation data of different environments is an important step toward adequate environmental monitoring, and it provides quick means to quantitatively check and determine possible radionuclide contamination by anthropogenic sources. Besides, such documentation is useful for decision making processes, assessment of dose rates to the public, epidemiological studies, and environmental regulations. This review summarizes the results of studies conducted on radioactivity in Nigerian environments. For most soil samples, the levels of radioactivity are well within the world averages of 33, 45, and 420 Bq kg^-1 for ²²⁶Ra, ²³²Th and ⁴⁰K, respectively. Other soil samples from regions such as Abeokuta in the southwest, and Jos in the northcentral have been described as high background radiation areas with radioactivity values comparable with those obtained from known high background radiation areas such as the Odisha (formerly Orissa) coast in India (with values reported as 350, 2,825, and 180 Bq kg^-1 for ²³⁸U/²²⁶Ra, ²³²Th, and ⁴⁰K, respectively). In some parts of Nigeria, surface and underground water sources used for drinking and other purposes also present elevated levels of ²²⁶Ra above the world range of 0.01 to 0.1 Bq l^-1 and the tolerable levels recommended by the World Health Organization and U.S. Environmental Protection Agency. Corresponding radiation doses due to measured radioactivities from different environments were estimated and compared with those reported in similar studies around the world. More so, the human and environmental health hazards that might be associated with the reported radioactivity in different environmental settings are discussed. The present report is expected to support authorities in developing appropriate regulations to protect the public from radiation exposure arising from environmental radioactivity. The report also examines other areas of consideration for future studies to ensure adequate radiation monitoring in Nigeria.

Methods for tentative determination of presence of artificial nuclides in air using NuRMS EGS air sampler and WIMP 120 gross alpha/beta counter

The determination of the presence of artificial radionuclides in the air is mainly accomplished by using gamma spectrometry analysis of filter samples. This work suggests very fast, reliable and efficient methods for tentative quantitative determination of the activity of artificial nuclides such as transuranic elements, strontium, yttrium, etc. in the air based only on the gross alpha and beta volume activity. The main aspect of these methods is to provide information about approximate results for the gross alpha and beta activity of air filters, thus it is convenient as a triage technique. Unlike gamma spectrometry, the methods are not qualitative but it allows the preliminary estimation of the presence of non-natural radionuclides. The influence of increment of the dust layer on self-absorption of alpha/beta particles was also studied. The methods are particularly suitable for screening situations where radionuclide identification is not necessary.

INVESTIGATION OF NATURAL RADIOACTIVITY AS A POSSIBLE DRIVER OF CANCER INCIDENCE IN PARAÍBA, NORTHEASTERN BRAZIL

An increase of health problems has been reported in the city of Triunfo, Paraíba, NE Brazil. This pattern has been attributed to environmental radiation since there are uranium deposits in the neighboring municipalities. The present study aimed to carry a radiometric survey in Triunfo to determine effective dose from external outdoor radiation exposure. The results were obtained through 'in situ' measurements using a gamma spectrometry system. The results ranged from 0.06 to 0.38 mSv/y, mean of 0.20 mSv/y. Due to the low value of the effective dose rate, we concluded that the area is characterized by low background radiation. Therefore, natural radioactivity is probably not directly influencing the increase in cancer incidence in the region. However, there is a need for complementary studies in this area to evaluate the dose from potential exposure to ingested and inhaled natural radionuclides from natural radioactivity in soil, rocks, vegetation and water.

NORM contaminated area identification using radionuclides activity concentration pattern in a soil profile

According to the requirements set by European BSS the exposure of humans and biota to ionizing radiation originating from natural radionuclides but under anthropogenically changed conditions should be managed within the same regulatory framework as other practices. Such situation creates the strong needs to have a reliable method to distinguish whether the particular case of natural radioactivity occurrence has resulted from human activity or it is pure natural phenomenon. In case of current activity of particular NORM industry there are no doubts however, in case of a legacy site, such question becomes crucial. One of the first warnings that the evaluated case has resulted from human deliberate or accidental activity is the lack of secular equilibrium among radionuclides constituting natural decay series. On the other hand some radionuclides, deposited on the ground surface due to radioactive fallout (e.g. caesium or lead isotope ²¹⁰Pb), create in long term perspective a specific pattern that remains characteristic for un undisturbed soil. Hence, it can be assumed that every observed change in it proves a human activity. In order to check this 19 soil profiles taken at undisturbed area and around different NORM heaps were analyzed. The measured radionuclides concentrations were used to anatomize any alternation of natural state, assess radionuclides migration and even investigate the history of a site of concern in the time horizon, usually long enough to identify any human activity. Results procured an easy method of identification different NORM sites based on observed ratios of particular natural radionuclides.