Pilot groundwater radon mapping and the assessment of health risk from heavy metals in drinking water of southwest, Nigeria

Determination of radon source in basaltic groundwater, using geochemical tracers and chemometric statistical analysis

Geochemical tracers such as stable isotopes are widely used in groundwater studies for determining aquifer connectivity and groundwater-surface water interactions. An analysis of dissolved radon (222Rn), major ions and trace element chemistry in groundwater was conducted in the fractured-rock aquifer system of Springbrook plateau, southeast Queensland, Australia. Chemical tracers were used to explore hydrological connectivity between the basalt formation and the underlying rhyolite formation. Water samples were collected from groundwater bores installed in both rock formations, from August 2021 to November 2023. Analysis revealed higher than expected concentrations of radon present in groundwater extracted from the basaltic aquifers (>20 Bq/L). A geochemical analysis of rock samples collected from the plateau, combined with a statistical analysis of water sample chemistry, confirmed the rhyolite formation as the primary source of radon. This indicates a strong hydrological connectivity between the rhyolite and basalt formations, such that the dissolved radon gas in groundwater is easily able to migrate through the network of fractures from the rhyolite formation into the overlying basalt formation. There are indications that seasonal rainfall events may be an important factor controlling the extent of vertical groundwater movement, as shown by temporal changes in radon concentrations. Hence, the groundwater aquifers in both formations should not be considered as discrete, disconnected systems. The geochemical tracers in both water and rock samples used in this investigation, combined with a chemometric statistical analysis, proved to be useful for identifying inter-aquifer connectivity in an area with no previous groundwater investigations.

Comprehensive investigation of carcinogenic radon levels in water within the Ikorodu axis of Lagos State, Nigeria

This study investigates radon concentration in drinking water from twenty samples collected at two tertiary Institutions in Ikorodu, Lagos State, using the RAD-7 detector. The objective is to evaluate the health risks associated with radon exposure, a known carcinogen linked to lung and stomach cancer. Radon in drinking water contributes to approximately 168 cancer deaths annually, predominantly from lung cancer due to inhalation of radon released indoors and stomach cancer from ingesting contaminated water. The measured radon concentrations ranged from 4.5 ± 1.1 Bq/m³ to 25.5 ± 2.1 Bq/m³, with 70% of samples exceeding the EPA's maximum contamination level of 11.1 Bq/L. Despite these high levels, the annual effective doses from ingestion and inhalation varied from 0.4545 to 24.37 μSv/y, remaining below the global average of 300 μSv/y and WHO limit of 100 μSv/y. While the presence of radon in Ikorodu's water sources indicates a radiological risk, the associated health risks are comparatively low according to international standards. These findings underscore the importance of ongoing monitoring and potential mitigation measures to ensure the continued safety of drinking water in the region.

Geographical distribution of radon and associated health risks in drinking water samples collected from the Mulazai area of Peshawar, Pakistan

Geospatial methods, such as GIS and remote sensing, map radon levels, pinpoint high-risk areas and connect geological traits to radon presence. These findings direct health planning, focusing tests, mitigation, and policies where radon levels are high. Overall, geospatial analyses offer vital insights, shaping interventions and policies to reduce health risks from radon exposure. There is a formidable threat to human well-being posed by the naturally occurring carcinogenic radon (222Rn) gas due to high solubility in water. Under the current scenario, it is crucial to assess the extent of 222Rn pollution in our drinking water sources across various regions and thoroughly investigate the potential health hazards it poses. In this regard, the present study was conducted to investigate the concentration of 222Rn in groundwater samples collected from handpumps and wells and to estimate health risks associated with the consumption of 222Rn-contaminated water. For this purpose, groundwater samples (n = 30) were collected from handpumps, and wells located in the Mulazai area, District Peshawar. The RAD7 radon detector was used as per international standards to assess the concentration of 222Rn in the collected water samples. The results unveiled that the levels of 222Rn in the collected samples exceeded the acceptable thresholds set by the US Environmental Protection Agency (US-EPA) of 11.1 Bq L-1. Nevertheless, it was determined that the average annual dose was below the recommended limit of 0.1 mSv per year, as advised by both the European Union Council and the World Health Organization. In order to avoid the harmful effects of such excessive 222Rn concentrations on human health, proper ventilation and storage of water in storage reservoirs for a long time before use is recommended to lower the 222Rn concentration.

A systematic review and meta-analysis of radon risk exposure from drinking water resources in Nigeria

Elevated radon concentrations in drinking water pose an increased risk of cancer among nonsmokers. A Monte-Carlo Simulation was employed to assess the effective dose and cancer risk associated with radon exposure in humans, utilizing a systematic review and meta-analysis of related studies. These studies were sourced from databases including PubMed, Web of Science, Scopus, Science Direct, and Google Scholar, focusing on drinking water from Nigeria's six geopolitical zones. The random effects models revealed a 222Rn concentration in drinking water of Nigeria at 25.01, with 95% confidence intervals (CI) of 7.62 and 82.09, indicating significant heterogeneity of (I2 = 100%; p < 0.001). The probabilistic risk of effective dose revealed a best-scenario (P 5%) at Kundiga and Magiro that exceeded the World Health Organization's (WHO) recommended effective dose limit of 200 µSv/y. Conversely, the worst-case scenario (P 95%) indicated concentrations surpassing the recommended limit at Kundiga, Edbe, Magiro, Ekiti, and Abeokuta. Excess Life Cancer Risk for infants, children, and adults attributed to the ingestion and inhalation of radon from various drinking water sources exceeded the recommended values of 0.2 x 10-3 established by the International Commission on Radiological Protection (ICRP) and the United Nations Scientific Committee on the Effect of Atomic Radiation (UNSCEAR). It underscores the necessity for treating radon-polluted water, employing methos such as aeration and granular activated carbon (GAC) processes.

Heavy metals in influent and effluent from 146 drinking water treatment plants across China: Occurrence, explanatory factors, probabilistic health risk, and removal efficiency

Heavy metals (HMs) in drinking water have drawn worldwide attention due to their risks to public health; however, a systematic assessment of the occurrence of HMs in drinking water treatment plants (DWTPs) at a large geographical scale across China and the removal efficiency, human health risks, and the correlation with environmental factors have yet to be established. Therefore, this study characterised the occurrence patterns of nine conventional dissolved HMs in the influent and effluent water samples from 146 typical DWTPs in seven major river basins across China (which consist of the Yangtze River, the Yellow River, the Songhua River, the Pearl River, the Huaihe River, the Liaohe River and the Haihe River) for the first time and removal efficiency, probabilistic health risks, and the correlation with water quality. According to the findings, a total of eight HMs (beryllium (Be), antimony (Sb), barium (Ba), molybdenum (Mo), nickel (Ni), vanadium (V), cobalt (Co) and titanium (Ti)) were detected, with detection frequencies in influent and effluent water ranging from 2.90 (Mo) to 99.30% (Ba) and 1.40 (Ti) to 97.90% (Ba), respectively. The average concentration range was 0.41 (Be)- 77.36 (Sb) μg/L. Among them, Sb (exceeding standard rate 8%), Ba (2.89%), Ni (21.43%), and V (1.33%) were exceeded the national standard (GB5749-2022). By combining Spearman's results and redundancy analysis, our results revealed a close correlation among pH, turbidity (TURB), potassium permanganate index (COD_Mn), and total nitrogen (TN) along with the concentration and composition of HMs. In addition, the concentration of HMs in finished water was strongly affected by the concentration of HMs in raw water, as evidenced by the fact that HMs in surface water poses a risk to the quality of finished water. Metal concentration was the primary factor in assessing the health risk of a single metal, and the carcinogenic risk of Ba, Mo, Ni, and Sb should be paid attention to. In DWTPs, the removal efficiencies of various HMs also vary greatly, with an average removal rate ranging from 16.30% to 95.64%. In summary, our findings provide insights into the water quality and health risks caused by HMs in drinking water.

Investigation of radioactivity level in drinking water resources and soil samples collected from the Hawraman villages, Iraq

In the present study, the RAD7 and NaI(Tl) techniques were utilized to determine the radon concentrations in drinking water resources and the natural primordial radionuclides in soil samples collected from Hawraman villages. The measured radon concentrations ranged from 1.7 ± 0.6 to 34.0 ± 2.8 Bq L^-1 with an arithmetic mean of 14.8 ± 1.2 Bq L^-1. This research demonstrates that roughly 54% of drinking water samples exceed the EPA-recommended level of 11.1 Bq L^-1. For adults, children, and infants, the total annual effective doses for the three types (D_ing, D_inh, and D_di) vary from 7.6 to 149.2 μSv y^-1 with an average of 65.0 μSv y^-1, 8.1-160.0 μSv y^-1 with an average of 69.7 μSv y^-1, and 10.5-207.0 μSv y^-1 with an average of 90.2 μSv y^-1.18.2%, 22.7%, and 36.4%, respectively, of the annual effective dose for adults, children, and infants exceeds the 100 μSv y^-1 level recommended by WHO and UNCEAR 2000. The activity concentrations of ²²⁶Ra, ²³²Th, and ⁴ K in soil samples varied from 10.9 ± 0.1 to 32.6 ± 0.2 Bq kg^-1, 18.3 ± 0.4 to 52.1 ± 0.6 Bq kg^-1, and 252.7 ± 2.5 to 585.6 ± 3.7 Bq kg^-1. The arithmetic mean concentrations of ²²⁶Ra, ²³²Th, and ⁴ K were determined to be 19.4 ± 0.2 Bq kg^-1, 36.2 ± 0.5 Bq kg^-1and 426.6 ± 3.2 Bq kg^-1, respectively. This research reveals that the average soil activity concentrations of ²²⁶Ra, ²³²Th, and ⁴ K are within the global average limits of 32, 45, and 420 Bq kg^-1, respectively. Comparing the concentrations to global averages, some soil samples revealed significant amounts of radionuclides, with around 18% of ²³²Th and 41% of ⁴ K. The computed radiological hazard indices of 100% of Ra_eq., 82% of D_out, 82% of E_out, and 95.5% of ELCR_out are all below the internationally recommended levels declared by Unscear 2000.

Hydrochemical and geological controls on dissolved radium and radon in northwestern Algeria hydrothermal groundwaters

This study presents the results of the first investigation on natural occurrence of radium and radon in Algerian thermal water systems. Activity concentrations of Rn and Ra isotopes were measured in sixteen hydrothermal springs of northwestern Algeria. Samples displayed high activities, especially for ²²²Rn, ²²⁴Ra and ²²⁶Ra (up to 377 × 10³ Bq/m³, 730 Bq/m³ and 4470 Bq/m³, respectively). Approximately, 50% of the investigated springs displayed activities of combined long-lived Ra (²²⁶Ra + ²²⁸Ra) in excess of the maximum contaminant level (MCL) of the WHO and EPA for drinking water. Factors controlling the distribution of radionuclides in the aquifer system are investigated. The observed correlation between Ra isotope and TDS suggests that adsorption/desorption is not the dominant process controlling the distribution of Ra in waters. Our results indicate that the excess SO₄^2- limits the concentration of dissolved Ba²⁺ and thereby, the elevated Ra activities in these hydrothermal systems are not simply limited by co-precipitation with BaSO₄ (barite). The data shows that Ra activities are likely dominated by the recoil process of parent isotopes in the aquifer solids. The minimal abundance of clay minerals and oxides in the aquifer, in addition to thermal activities in northwestern Algeria, significantly enhances the mobilization of Ra into waters.

Evaluation of soil-gas radon concentrations from different geological units with varying strata in a crystalline basement complex of southwestern Nigeria

The aim of this study is to determine the variation of soil-gas radon concentrations from different rock formations in Ogbomoso, southwestern Nigeria. The radon concentrations at different five geological domains in Ogbomoso are determined with respect to depth. The measurements varied from the surface (0 cm) to 100 cm depth, with an interval of 20 cm. At all the geological domains (Porphyroclastic, Granite, Quartzite, Migmatite and Banded gneiss), radon has its minimum emission over migmatite at 0 cm, while its maximum emissions occured over granite and banded gneiss at 80 cm. The overall soil-gas radon concentrations in Ogbomoso varied from 0.06 to 26.5 kBq/m³, which is within the natural limit of 0.4 to 40 kBq/m³ based on the International Commission on Radiological Protection's recommendation. An F-ratio of 6.989 and a p-value of 0.001 were obtained for the first inferential hypothesis, while an F-ratio of 2.489 and a p-value of 0.076 were obtained for the second inferential hypothesis using ANOVA test. The post hoc (using Tukey HSD and Duncan) tests revealed that at 60 + cm, depth controls the level of radon concentrations being emanated from the subsurface. The pollution index in Ogbomoso is of level 1 at 80 cm and level 0 (safe limit) at other depths. In conclusion, the soil-gas radon emission depends on the local geology and lithological sequences (depths). Cracks that could act as passage for indoor radon at the floors of the buildings around the polluted zones should be avoided in order to have a sustainable city.