A research team collected sand from 33 locations stretching along the entire 354-kilometre Bulgarian coastline, from the village of Durankulak near the Romanian border down to Rezovo at the Turkish frontier. Roughly 200 kilometres of this shore consists of sandy beaches, formed over millennia by the weathering and erosion of igneous and metamorphic rocks in the surrounding terrain. Because such sediments naturally carry traces of radioactive elements from the Earth’s crust, measuring them offers a direct window into the radiological environment that residents and tourists experience every day.

Each sample was cleaned and dried in a laboratory oven at temperatures up to 60 degrees Celsius, then sealed into cylindrical containers for gamma-spectrometric analysis. The measurements relied on a semiconductor detector with a 60-cubic-centimetre crystal, operating at 1 kilovolt with a relative efficiency of 4.5 percent for the caesium-137 gamma line. To keep ambient background radiation from contaminating the results, the detector was wrapped in layered shielding of lead, aluminium, cadmium and polyethylene, and the resulting spectra were processed with dedicated software that calculated each isotope’s specific activity from its characteristic gamma peaks.

The analysis identified the classic natural radioactive fingerprint of beach sands: isotopes from the uranium-radium and thorium decay series, detected through gamma lines of daughter products such as lead-214, bismuth-214, actinium-228 and thallium-208, plus the primordial isotope potassium-40, identified by its 1460.80-kiloelectronvolt gamma line. On average, the sands contained 11.62 becquerels per kilogram of uranium-238, 6.82 becquerels per kilogram of thorium-232 and 396.55 becquerels per kilogram of potassium-40. Every one of these figures falls below the global averages of 35, 30 and 370 becquerels per kilogram respectively, as compiled by the United Nations Scientific Committee on the Effects of Atomic Radiation.

The spread between individual beaches tells its own story. Uranium-238 activities ranged from 5.80 becquerels per kilogram at Rezovo Beach to 28.30 at Irakli Beach, while thorium-232 mostly stayed between 3 and 12 becquerels per kilogram, with Irakli again standing out at 19.06. Potassium-40, the most abundant of the three natural isotopes, varied from roughly 209 to 705 becquerels per kilogram, peaking at Rapongi Beach in Varna and dipping lowest near the village of Tyulenovo. Frequency analysis showed that 84 percent of uranium measurements clustered between 7 and 16 becquerels per kilogram, 87 percent of thorium values sat between 5 and 10, and 70.5 percent of potassium readings fell between 240 and 550.

One artificial isotope also made an appearance. Caesium-137, a fission product of atmospheric nuclear weapons tests and reactor accidents, was detected in 11 of the 33 samples at concentrations between 1.4 and 3.4 becquerels per kilogram, with the highest value at Kavarna Beach. That average of 3.16 becquerels per kilogram is modest by any measure, and consistent with recent regional surveys, which have recorded caesium-137 in Black Sea sands at anywhere from 0.8 to 12.3 becquerels per kilogram. Its presence is a faint echo of mid-twentieth-century fallout in a basin that has long been considered one of the more radioactively studied marine environments in the world.

Using the GPS coordinates of every sampling point, the team generated geostatistical distribution maps that reveal how radioactivity varies along the coast. Uranium-238 proved fairly uniform, with its maximum at Irakli. Thorium-232 showed its lowest values in the northern Black Sea, with a single pronounced hot spot at Irakli Beach. Potassium-40 peaked near Tyulenovo and the Rai campsite at Kamchiya, while caesium-137 reached its highest concentrations around Kranevo village and the central beach of Golden Sands, with levels gradually rising toward the southern stretch of the coast.

Beyond raw isotope counts, the researchers calculated a battery of internationally recognised radiation hazard indices, including radium equivalent activity, gamma index, external and internal hazard indexes, outdoor absorbed dose rate, annual effective dose, excess lifetime cancer risk and absorbed dose rate in air. The averages were unremarkable in the best sense: an absorbed dose rate in air of 26.32 nanogray per hour against a world average of 84, an annual effective dose of 0.16 millisieverts per year against a global benchmark of 0.48, and a radium equivalent activity of 51.90 becquerels per kilogram, far under the 370 limit. External and internal hazard indexes came in at 0.14 and 0.17, both well below the safety threshold of one, and the estimated excess lifetime cancer risk of 0.11 per thousand sat below the reference value of 0.29. The maps of these indices flagged mild hot spots at Tyulenovo, the Rai campsite and Primorsko’s southern beach, with the lowest readings at Rezovo.

The statistical treatment went further than simple averages. Pearson correlation analysis across twelve radiological variables showed that 83 percent of the coefficients fell into the high or very high correlation ranges, confirming that the calculated hazard indices move in lockstep with the underlying isotope concentrations. Notably, thorium-232 correlated only weakly with the radiological parameters, leading the authors to conclude that thorium and its decay products exert the least influence on the natural radioactivity of these beaches. A hierarchical cluster analysis reinforced this picture, grouping ten radiological factors together while potassium-40 stood apart in its own cluster, and linking uranium-238 and thorium-232 most closely to the overall radiological parameter levels.

For beachgoers, the practical takeaway is simple: the sands of the Bulgarian Black Sea coast deliver a radiation dose well within internationally published limits set by UNSCEAR, the NEA-OECD and the International Commission on Radiological Protection. For scientists, the study provides a detailed baseline, complete with distribution maps and statistical relationships, against which any future changes in the coastal radiological environment can be judged, whether they stem from erosion, coastal development or the slow decay of legacy fallout still working its way through the Black Sea ecosystem.

Subject of Research: Radioactivity levels and radiation hazard indices in beach sands along the Bulgarian Black Sea coast

Article Title: Investigation of the radioactivity of sands collected from Bulgarian Black Sea coast

Article References: Arhangelova, N., & Salim, S. (2026). Investigation of the radioactivity of sands collected from Bulgarian Black Sea coast. BioRisk, 24, 103-117. https://doi.org/10.3897/biorisk.24.178091

Image Credits: AI Generated

DOI: 10.3897/biorisk.24.178091

Keywords: radioactivity, Black Sea, Bulgaria, beach sand, gamma spectrometry, radionuclides, caesium-137, potassium-40, uranium-238, thorium-232, radiation hazard indices, radiological assessment

Naturally occurring radioactive materials, often abbreviated as NORM, are present in virtually all soils and rocks on Earth. The three radionuclides at the center of this investigation are potassium-40, a primordial isotope that makes up a tiny fraction of all natural potassium; radium-226, a member of the uranium-238 decay chain; and thorium-232, the head of its own long decay series. These isotopes are generally harmless at the low concentrations found in most agricultural land, but mining activities can concentrate them. When excavators and hand diggers bring deep material to the surface, process ore, and leave tailings exposed to wind and water, the normal geochemical balance is disturbed, and the radiation environment of a community can change in ways that are impossible to sense without instruments.

To measure those concentrations, the team collected soil samples from the three study regions and analyzed them using a sodium iodide detector doped with thallium, a workhorse instrument of gamma-ray spectroscopy. The NaI(Tl) detector registers the characteristic gamma photons emitted by each radionuclide and its decay products, allowing researchers to convert counts into activity concentrations expressed in becquerels per kilogram of soil. The results placed the average activity concentrations at 18.79 plus or minus 0.91 Bq/kg for radium-226, 7.87 plus or minus 1.23 Bq/kg for thorium-232, and 346.39 plus or minus 10.35 Bq/kg for potassium-40. These figures provide the essential input for any dose assessment, because the intensity of exposure in a contaminated landscape is governed first and foremost by how much radioactive material is actually present.

Measuring concentrations, however, is only the first step. The central question for radiation protection is what those numbers mean for human health over decades of exposure. To answer it, the researchers turned to the RESRAD code, short for residual radioactivity, a simulation package developed originally to support the cleanup of contaminated sites and now a standard tool for translating soil radioactivity into dose and risk estimates. RESRAD models the full web of exposure pathways that connect buried or surface-deposited radionuclides to human beings: direct external gamma irradiation from the soil itself, inhalation of dust particles carrying radioactive atoms, ingestion of soil, and the transfer of radionuclides through water, crops, and animal products into the food chain. By parameterizing the model with site-specific conditions and running it across a one-hundred-year horizon, the team could project how risk accumulates for two distinct populations, artisanal miners who spend long hours in intimate contact with disturbed soil, and resident farmers whose exposure comes through tilling, planting, and living on the same land.

The simulation results are striking for their clarity. Across the entire evaluated time period, from one to one hundred years, the excess lifetime cancer risk ranged from 2.33 times ten to the minus six to 5.40 times ten to the minus six. The minimum value was associated with thorium-232, while the maximum was driven by radium-226. In other words, of the three radionuclides studied, radium-226 emerged as the dominant contributor to long-term cancer risk in the mining soils, followed by thorium-232, with potassium-40 playing a comparatively smaller role despite its higher activity concentration. This inversion is scientifically meaningful: activity concentration alone does not determine risk, because each radionuclide carries its own decay energy, its own decay chain behavior, and its own dose coefficients that describe how effectively a given intake or external exposure translates into absorbed energy in human tissue.

The pathway analysis added another layer of insight. According to the simulation, the dominant exposure routes were direct radiation from the soil, both the direct gamma shine from the ground surface and the airborne component, together with inhalation. This finding matters enormously for practical protection. If inhalation and direct external exposure dominate, then the most effective interventions are those that reduce dust generation and limit time spent on freshly disturbed, unshielded soil. Simple measures such as wetting down working areas, wearing respiratory protection, and restricting the processing of ore in enclosed or poorly ventilated spaces can disproportionately reduce dose when inhalation is a leading pathway. Conversely, if food-chain transfer had dominated, the response would have focused instead on soil remediation and crop selection, a very different and more expensive set of actions.

The excess lifetime cancer risk metric itself deserves explanation, because it is the number that ultimately connects environmental measurement to human fate. The ELCR represents the probability, over and above the baseline cancer rate in any population, that a person will develop fatal cancer as a result of a lifetime of exposure to a given radiation source. Values on the order of ten to the minus six, as found in this study, correspond to roughly one additional cancer case per million exposed individuals, a magnitude that international guidance often treats as a threshold of concern for prolonged public exposure. The fact that the modeled risks in the Niger State mining regions fall within this low range is reassuring at first glance, but the authors emphasize that the findings are intended to inform radiation protection decisions, and the cumulative burden across large populations of miners and farmers, combined with other hazards of artisanal mining, is precisely the kind of information regulators need before risks grow.

The context of artisanal gold mining in Nigeria gives the study its urgency. Artisanal and small-scale mining provides livelihoods across parts of West Africa but operates largely outside formal regulatory frameworks, with minimal environmental monitoring and little occupational health oversight. Previous research in the same region has documented serious chemical hazards, including mercury contamination in soil at artisanal gold mine sites in Niger State, where the metal is used to amalgamate gold. The new radiological assessment adds a third dimension to this picture of cumulative environmental burden, showing that the same soils that carry toxic metals also carry measurable quantities of primordial and decay-chain radionuclides. For communities where mining and agriculture coexist on the same land, the combined evidence paints a portrait of chronic, low-level exposure that is easy to ignore precisely because no single measurement triggers alarm.

Methodologically, the study demonstrates the value of pairing direct spectroscopic measurement with process-based simulation. The NaI(Tl) measurements anchor the model in reality, capturing the actual gamma-emitting inventory of the soil, while RESRAD extends that snapshot across time and across exposure scenarios that would be impossible to observe directly. The one-hundred-year simulation window is particularly important for radionuclides like radium-226 and thorium-232, whose long half-lives mean that contamination does not simply decay away within a human generation. The authors note that the RESRAD-OFFSITE software used for the simulations is publicly available and that the model inputs are described in the article, an openness that allows other researchers to replicate the analysis in other mining regions where NORM data are scarce.

The broader significance of the work lies in its contribution to a growing global dataset on natural radioactivity in mining environments. Comparable assessments have been carried out around gold mines in Ghana, coal mining areas in Brazil, granite quarries in Iran, and iron beneficiation plants in China, each adding pieces to a picture of how extractive industries redistribute the Earth’s natural radioactivity into human contact. The Niger State study stands out for its explicit comparison of two vulnerable populations, miners and farmers, and for its pathway-resolved risk estimates that point directly toward mitigation. As demand for gold and other minerals continues to drive informal mining deeper into rural landscapes, studies of this kind provide the evidence base for radiation protection policies that can be implemented before, rather than after, health effects emerge. For the farming and mining communities of north-central Nigeria, the message of the numbers is measured but clear: the risk today is small, the dominant pathways are known, and the window for inexpensive prevention is open.

Subject of Research: Assessment of radiation dose and excess lifetime cancer risk from naturally occurring radionuclides in soil at artisanal gold mining sites in Nigeria using the RESRAD code

Article Title: Assessment of effective dose and radiation risk due to 226Ra, 40K, and 232Th exposure within the soil of artisanal gold mine using the RESRAD code

Article References: Muhammad, A., & Abbasi, A. (2026). Assessment of effective dose and radiation risk due to 226Ra, 40K, and 232Th exposure within the soil of artisanal gold mine using the RESRAD code. Environmental Monitoring and Assessment, 198(10), Article 1039. https://doi.org/10.1007/s10661-026-15887-w

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15887-w

Keywords: natural radioactivity, radium-226, thorium-232, potassium-40, RESRAD, artisanal gold mining, excess lifetime cancer risk, Nigeria, gamma-ray spectrometry, radiation protection, NORM, exposure pathways

The research, published in Environmental Monitoring and Assessment, was carried out by a team from Hassan II University, the Moroccan National Centre for Nuclear Energy, Science and Technology (CNESTEN) and the National Institute of Agricultural Research, working within an International Atomic Energy Agency coordinated research project on radionuclide transfer in arid and semiarid environments. Led by Zineb Elaboudi, the scientists sampled soil and nine commonly consumed crops, including coriander, red pepper, potato, onion, pomegranate, cardoon, beet, tomato and eggplant, from farmland in a semiarid Moroccan agricultural area. Their goal was to quantify activity concentrations, calculate soil-to-plant concentration ratios and estimate the potential annual effective dose that people could receive from eating locally grown food.

The analytical work relied on high-resolution alpha- and gamma-spectrometry using high-purity germanium detectors, instruments capable of distinguishing the characteristic energy signatures of individual isotopes even at very low concentrations. The team measured eight radionuclides in both soil and plants: polonium-210, thorium-234, radium-226, thorium-228, radium-228, lead-210, potassium-40 and cesium-137. Together these isotopes span the full spectrum of environmental radioactivity, from members of the uranium and thorium decay chains that have leached slowly through bedrock for millennia, to potassium-40 dispersed uniformly through all living tissue, to cesium-137, a fission product whose global fallout from mid-twentieth-century nuclear weapons testing still lingers in surface soils.

In the soil, activity concentrations painted a picture of typical natural background. Polonium-210 ranged from 16.37 to 39.59 becquerels per kilogram, thorium-234 from 6.21 to 29.15, radium-226 from 4.84 to 26.26, thorium-228 from 9.37 to 46.04, radium-228 from 10.10 to 51.04, and lead-210 from 5.92 to 31.39. Potassium-40, as expected, dominated with values between 107.21 and 434.20 becquerels per kilogram, while cesium-137, the sole anthropogenic contributor, registered only 1.15 to 2.98 becquerels per kilogram, a faint residue of atmospheric fallout rather than any local contamination source.

Inside the plants, the story changed dramatically. Activity concentrations were generally far lower than in the underlying soil, with polonium-210 between 0.12 and 4.76 becquerels per kilogram, radium-226 between 0.36 and 5.89, and thorium-228 between 0.22 and 1.61. Potassium-40, however, ran in the opposite direction, reaching 386.33 to 3265.53 becquerels per kilogram, sometimes exceeding its soil concentration. The reason is biochemical rather than radiological: potassium is an essential plant macronutrient, recruited in large quantities to regulate osmotic pressure and enzyme function, and potassium-40 constitutes a fixed fraction of all natural potassium. Because the isotope cannot be separated chemically from its stable siblings, plants that accumulate potassium necessarily accumulate its radioactivity. Meanwhile thorium-234, radium-228, lead-210 and cesium-137 mostly fell below detection limits in the crops, indicating that roots act as effective barriers against these species.

The concentration ratio, defined as the activity concentration in plant tissue divided by that in dry soil, is the single most important parameter in radiological dose models, and the Moroccan values revealed striking crop-specific differences. Ratios spanned 0.01 to 0.14 for polonium-210, 0.02 to 0.43 for radium-226, and 0.01 to 0.17 for thorium-228, but climbed as high as 20.03 for potassium-40. Two crops stood out as the strongest accumulators: cardoon, a thistle-like vegetable with deep roots and a place of honor in North African cuisine, and eggplant. Elevated transfer in these species suggests that rooting depth, plant family physiology and nutrient demand all shape which isotopes cross the root membrane, a finding consistent with observations from Syria, Saudi Arabia, Abu Dhabi and other dry regions where comparable studies have been conducted.

Perhaps the most scientifically valuable contribution lies in the correlation analysis linking radionuclide uptake to soil chemistry. The researchers found strong interrelationships among the measured isotopes and demonstrated that transfer processes are governed primarily by soil physicochemical properties, particularly organic matter content, cation exchange capacity and the suite of exchangeable cations held on clay and humus surfaces. These parameters control how tightly radionuclides are bound to soil particles and therefore how available they are for root uptake. In contrast, carbonate content and salinity tended to restrict radionuclide mobility, effectively locking the isotopes in place. This has a counterintuitive implication for semiarid agriculture: the very conditions that make soils challenging for crop productivity, including high carbonate levels and salt accumulation under intense evaporation, may also suppress the movement of radioactive elements into the food chain.

The study also estimated the potential annual effective dose from food ingestion, the standard metric used by the International Commission on Radiological Protection to translate environmental measurements into health-relevant terms. By combining crop activity concentrations with consumption rates and isotope-specific dose coefficients, the team could assess whether locally grown vegetables contribute meaningfully to the radiation burden that residents already receive from cosmic rays, radon and terrestrial gamma radiation. The dominance of potassium-40 in plant tissues means it inevitably drives much of the ingested dose, yet because the human body maintains potassium homeostasis, biologically regulated excretion keeps the internal burden from this isotope essentially constant regardless of dietary source, a nuance that distinguishes potassium-40 from radium or polonium, which follow bone and soft-tissue metabolism and are treated with greater regulatory caution.

For the wider scientific community, the Moroccan dataset fills a recognized gap. The IAEA has repeatedly noted that most soil-to-plant transfer parameters in its handbooks derive from temperate European and North American ecosystems, while arid and semiarid environments, home to a large share of the world’s irrigated agriculture, remain underrepresented. Studies from Turkey, Jordan, Nigeria, Vietnam, Australia and now Morocco are steadily building the evidence base needed to adapt radiological environmental impact assessment to dry climates. The finding that organic matter and cation exchange capacity promote transfer while carbonates and salinity suppress it offers modelers concrete, measurable soil descriptors that can be incorporated into transfer predictions without requiring site-specific experiments at every location.

The practical message for consumers is reassuring. Cesium-137 was barely detectable, the natural radionuclides were mostly well below levels of concern, and the estimated doses fall within the range regarded as normal background exposure from food. Yet the research carries lasting value beyond its immediate conclusions. As phosphate fertilizer use, water scarcity and climate change reshape agriculture across the semiarid world, understanding the soil chemistry that governs radionuclide mobility becomes essential for protecting both food safety and the environmental systems that sustain it. This Moroccan study, rooted in rigorous gamma and alpha spectrometry and framed by international collaboration, demonstrates that even the quiet radioactivity of an ordinary vegetable patch can be measured, modeled and managed with precision.

Subject of Research: Soil-to-plant transfer of natural and artificial radionuclides and associated radiological doses in semiarid Moroccan agriculture

Article Title: Radiological impact of radionuclides in Moroccan food crops under semiarid conditions

Article References: Elaboudi, Z., Aouidi, S. E., Saadi, R., Benkdad, A., Mouridi, Z. E., Laissaoui, A., Madinzi, A., & Souabi, S. (2026). Radiological impact of radionuclides in Moroccan food crops under semiarid conditions. Environmental Monitoring and Assessment, 198(11), Article 1160. https://doi.org/10.1007/s10661-026-15992-w

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15992-w

Keywords: radionuclides, soil-to-plant transfer, concentration ratio, potassium-40, radium-226, polonium-210, cesium-137, semiarid agriculture, Morocco, gamma spectrometry, radiological dose, soil chemistry

The team collected thirty-eight soil samples from across the district, preparing them under controlled laboratory conditions before analysis. The measurement technique of choice was gamma ray spectrometry using a high-purity germanium detector, an instrument prized in radiation science for its exceptional energy resolution. Unlike simpler sodium iodide detectors, high-purity germanium crystals can separate the closely spaced gamma ray lines emitted by different radionuclides, allowing researchers to identify and quantify specific isotopes with confidence. In this study, the detector was calibrated and used to measure the activity concentrations of three radionuclides that dominate the natural radiation environment: potassium-40, thorium-232, and radium-226, the latter serving as a proxy for the uranium decay chain in soil.

The results reveal a clear hierarchy among the three isotopes. Potassium-40, a long-lived isotope that makes up a tiny fraction of all natural potassium, showed the highest activities, ranging from 342 plus or minus 10 to 760 plus or minus 16 becquerels per kilogram, with an average of 568 becquerels per kilogram. Thorium-232 activities ranged from 35 plus or minus 1.0 to 83 plus or minus 3.4 becquerels per kilogram, averaging 55 becquerels per kilogram, while radium-226 ranged from 48 plus or minus 1.9 to 90 plus or minus 3.7 becquerels per kilogram, with a mean of 65 becquerels per kilogram. These values sit within the ranges typically reported for soils worldwide, though the upper end of the potassium-40 distribution is notable, reflecting the mineralogy of the local geological formations from which the soils derive.

What makes the study more than a simple catalog of numbers is its statistical treatment of the data. Because environmental radioactivity measurements are frequently skewed by outliers and by the heterogeneous nature of soil, the authors first applied the Shapiro-Wilk test to assess whether the activity distributions followed a normal distribution. This test, widely regarded as one of the most powerful normality tests for moderate sample sizes, informs which subsequent statistical tools are appropriate. The researchers then employed the Spearman rank correlation test, a non-parametric method that measures monotonic relationships without assuming linearity or normality, to probe whether the three radionuclides vary together across sampling sites. Strong positive correlations between radionuclides can indicate a shared mineralogical origin, for example when uranium, thorium, and potassium-bearing minerals are concentrated together in the same parent rocks and weathering products.

To investigate whether the underlying geology, or lithology, exerts a measurable influence on radionuclide levels, the team turned to the Kruskal-Wallis test, a non-parametric analysis of variance that compares multiple groups without requiring normally distributed data. Gurugram’s geology is diverse, with the Aravali hill range skirting the district and alluvial plains covering much of its area, so differences in radionuclide concentrations between zones with different geological character are scientifically expected. The combination of these tests, descriptive statistics, normality assessment, rank correlation, and group comparison, represents a methodologically rigorous framework that is increasingly standard in environmental radioactivity studies, allowing researchers to distinguish genuine geological signals from random spatial variation.

Beyond characterizing the distribution of radionuclides, the study translated its measurements into quantities that matter for human health. From the measured activity concentrations, the authors calculated the absorbed gamma dose rate in air, which describes the energy deposited by gamma radiation per unit mass of air at ground level, and from that the annual effective dose rate for both indoor and outdoor exposure scenarios. Indoor doses are typically weighted more heavily in radiological assessments because people spend the majority of their time inside buildings, where gamma rays from construction materials derived from soil add to the outdoor background. The comparison of these derived doses with reference values established by international agencies such as the United Nations Scientific Committee on the Effects of Atomic Radiation provides the practical yardstick for judging whether the measured levels pose any concern to the public.

The team also computed two widely used screening indices. The gamma index, which ranged from 0.48 to 0.95 across the sampled soils, is designed to flag materials whose gamma radiation could become significant if used in building construction; values below unity are generally considered acceptable under international guidance. The alpha index, which ranged from 0.24 to 0.45, serves as a screening tool for potential radon inhalation hazards associated with radium-226 content, since radon-222 is a radioactive gas in the uranium decay chain that can accumulate in enclosed spaces. Both indices remained below their conventional thresholds across all thirty-eight samples, indicating that the natural radioactivity of Gurugram’s soils falls within the range considered safe for ordinary exposure and typical construction use.

The Gurugram survey is the latest entry in a growing body of work on natural radioactivity across northern India, much of it involving overlapping research groups. Previous studies by the same lead author and collaborators have examined radon and thoron exhalation from Gurugram soils, radionuclides in the soils of neighboring Palwal district, seasonal and geological influences on gamma radiation in Faridabad, and radon doses from groundwater in the same region. Parallel investigations elsewhere in Haryana and Punjab, including assessments of Rohtak, Jind, Bathinda, and Sirsa, and geospatial surveys of urban soils in Chennai, contribute to a national picture in which terrestrial gamma dose varies principally with local geology rather than with human activity. Such baseline datasets are valuable not only for radiation protection but also as reference points against which any future anthropogenic contamination, whether from industrial activity, construction, or accidents, could be detected and quantified.

For the residents of Gurugram, the practical message of the study is reassuring: the natural radioactivity of the district’s soils, from the potassium-rich alluvium to the thorium-bearing sediments near the Aravalis, produces radiation doses that international agencies would classify as within normal background levels. But the scientific significance runs deeper. As urbanization transforms land use across the National Capital Region, soils that once lay undisturbed are being excavated, processed into building materials, and incorporated into the homes and offices of millions. Understanding the radiological properties of that raw material, and the geological factors that control its variability, is a quiet but essential piece of public health infrastructure. With rigorous measurement, transparent statistics, and comparison against international standards, this study demonstrates how even an invisible, omnipresent hazard can be brought into sharp, quantifiable focus.

Subject of Research: Measurement of natural radionuclides and radiological hazard assessment in soils of Gurugram district, India

Article Title: Monitoring of natural radionuclides in soil of District Gurugram, Haryana (India), by gamma spectrometry and statistical analysis

Article References: Singh, B., Gupta, U., Kant, K., Yadav, S., & Tanwer, N. (2026). Monitoring of natural radionuclides in soil of District Gurugram, Haryana (India), by gamma spectrometry and statistical analysis. Environmental Monitoring and Assessment, 198(10), Article 1106. https://doi.org/10.1007/s10661-026-15925-7

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15925-7

Keywords: natural radioactivity, gamma spectrometry, potassium-40, thorium-232, radium-226, soil, Gurugram, Haryana, radiation dose, gamma index, statistical analysis, environmental monitoring

The study, published in the journal Discover Oceans, involved measuring gamma radiation at thirty locations spread across an area of roughly two kilometres by six hundred metres, arranged on an imaginary grid with two hundred metres between adjacent points. The researchers used a portable sodium iodide detector sealed inside a PVC pipe to record total gamma counts directly on the beach, logging each position with a handheld GPS receiver. Back in the laboratory, sediment collected from the same thirty sites was dried, sieved and analysed with a high-resolution germanium detector to quantify specific radionuclides. The in-situ counts ranged from 1800 to 6498 counts per minute, and the interpolated map showed that radioactivity was noticeably higher toward the south-west of the beach than the north-east.

What makes the pattern scientifically interesting is that different radionuclides behave in opposite ways depending on the size of the sand grains they inhabit. In the finest fraction studied, grains between 53 and 100 micrometres, the mean activity concentrations of radium-226, radium-228 and potassium-40 were 151.2, 369.4 and 209.7 becquerels per kilogram respectively. In the dominant medium fraction, between 101 and 250 micrometres, the same isotopes averaged just 28.7, 60.6 and 272.6 becquerels per kilogram. In other words, radium concentrates in fine grains while potassium-40 favours coarse ones, a split that reflects two entirely different geochemical stories.

The radium story is one of surface chemistry. Radium-226 and radium-228 are daughter products of the uranium-238 and thorium-232 decay chains, and both isotopes are strongly adsorbed onto particle surfaces. Fine grains carry far more surface area per unit mass than coarse grains, so they adsorb more radium from seawater and pore fluids. Potassium-40 behaves differently: it is an integral constituent of silicate minerals derived from igneous rocks, and its compatibility with silica means it travels locked inside the mineral lattice rather than clinging to grain surfaces. Coarse sediments, being richer in such minerals and less easily washed back out by the tide, end up enriched in potassium-40. The tidal sorting mechanism is simple but effective: waves wash lighter fine grains away and leave heavier particles behind on the beach.

To characterise the sediments chemically, the team used energy-dispersive X-ray fluorescence on the medium grain fraction, which makes up more than seventy percent of the sediment by weight at most locations. The dark grey sand proved mineral-rich, with iron, aluminium, calcium, magnesium, titanium, potassium, vanadium, manganese, zirconium, chromium and lanthanum as the major elements. Mean iron concentration reached about 84,900 parts per million, with aluminium near 54,000 and calcium around 50,000 parts per million. This composition points to substantial heavy-mineral content, the kind of material that waves and currents concentrate into placers and that can markedly raise local radioactivity, as seen dramatically in the monazite-rich black sands of Kerala on India’s south-west coast.

Compared with other Indian and international beaches, Jampore sits in a middle ground. Kerala’s high-background radiation area shows thorium-232 activities that can reach thousands of becquerels per kilogram, far beyond anything measured at Daman. Tamil Nadu beach sands typically report radium-226 between 13 and 198 becquerels per kilogram, while the Odisha and Andhra coasts fall in the tens to low hundreds. Globally, beaches in Ghana, Turkey and Thailand report broadly similar values, with radium isotopes in the tens and potassium-40 in the low hundreds of becquerels per kilogram. Jampore’s fine fraction is moderately elevated relative to many of these sites, but remains well below the classical high-background zones, meaning the beach is radiologically ordinary while still being dynamically informative.

The most consequential finding concerns the ratio of the two radium isotopes. Across the fine fraction the radium-226 to radium-228 ratio ranged from 0.29 to 0.55, and in the medium fraction from 0.39 to 0.61. Crucially, zones with lower ratios coincided with higher total gamma counts. Building on earlier work in the Yangtze Estuary, where smaller radium ratios were linked to sediment accretion, the researchers interpret the low-ratio, high-count areas of Jampore beach as zones where sand is accumulating. The strong linear correlation between the two radium isotopes, with a coefficient of determination of 0.9878, suggests they share a common origin and are governed by the same adsorption and desorption processes, which makes their ratio a stable and interpretable indicator.

The in-situ measurements also proved to be a surprisingly faithful proxy for laboratory analysis. Correlation plots showed that the spatial pattern of total gamma counts closely mirrors the distributions of both radium-226 and radium-228, but not potassium-40. The reason lies in nuclear structure: the uranium and thorium series emit multiple high-intensity gamma lines, including strong peaks at 609.3 and 1764.5 kiloelectronvolts for the radium-226 chain and at 583.2 and 2614.5 kiloelectronvolts for the radium-228 chain, whereas potassium-40 emits only a single gamma ray at 1460.82 kiloelectronvolts with a modest ten percent emission probability. The integrated field signal is therefore dominated by the radium chains, which is precisely what makes a rapid field survey with a portable detector a viable stand-in for detailed laboratory spectrometry when the goal is mapping sediment regimes.

The broader motivation is methodological. Since 1954, investigations of coastal sediment dynamics have relied on artificial radiotracers produced in nuclear reactors, materials that are effective but burdened by public concern and strict regulatory clearance requirements from nuclear safety authorities. Natural radionuclides embedded in the sediment offer an alternative that requires nothing to be released. Researchers in Spain, the Canary Islands, South Africa and elsewhere have already proposed radium isotopes and lead-210 as tracers of erosion and accretion, and the Indian team frames its Jampore survey as a first step toward establishing a radiometric database and a methodology for using natural isotopes as tracers along Indian coasts. The data could also serve as benchmarks against which numerical sediment transport models can be validated, increasing confidence in their predictions.

For a beach flanked by the mouths of the Daman Ganga and Kolak rivers, where fluvial supply, wave sorting and monsoon-driven erosion continuously redistribute the sand, the ability to read accretion and erosion directly from the sediment’s own radioactivity is a genuinely practical tool. Harbour dredging, dumping-site selection and coastal protection all depend on knowing where sediment goes, and a technique that replaces costly and regulated artificial tracers with a portable detector and a GPS unit could change how coastal engineers gather that knowledge. The Jampore map is a modest survey of one four-and-a-half-kilometre beach, but it demonstrates a principle with wide reach: every shoreline already carries its own radioactive diary of movement, and learning to read it may be as simple as walking the sand with a detector in hand.

Subject of Research: Spatial distribution of natural radioactivity in beach sediments as a tracer of coastal sediment dynamics

Article Title: Investigation of distribution pattern of natural radioactivity in the sediments of Jampore beach, Daman, India

Article References: Biswal, J., Goswami, S., Yadav, V. B., Sartandel, S. J., Samantray, J. S., Pulhani, V., & Sharma, V. K. (2026). Investigation of distribution pattern of natural radioactivity in the sediments of Jampore beach, Daman, India. Discover Oceans, 3(1), Article 12. https://doi.org/10.1007/s44289-026-00124-6

Image Credits: AI Generated

DOI: 10.1007/s44289-026-00124-6

Keywords: natural radioactivity, Jampore beach, Daman, sediment dynamics, gamma spectrometry, radium-226, radium-228, potassium-40, heavy minerals, coastal erosion, accretion, EDXRF

The research team, led by geologists from Ekiti State University and collaborating institutions in Nigeria and China, collected 274 samples in December 2023—137 soils and 137 stream sediments—using a hand auger at depths of zero to ten centimeters, the layer where human contact with radionuclides is most direct. The sampling grid covered more than seventy percent of the study area, which lies between the towns of Gana, Pako, Korgadzhi, and Mokwa, and spans terrain underlain by granite gneiss, quartzo-feldspathic gneiss, quartz mica schist, quartzite, and metagraywacke, all intruded by Neoproterozoic Pan-African granitic rocks. These metamorphic and igneous units contain varying amounts of radioactive minerals, which weathering steadily releases into nearby soils and drainage systems.

Analysis was performed using high-performance liquid chromatography coupled with inductively coupled plasma-mass spectrometry at the Bureau Veritas Minerals Laboratory in Vancouver, Canada, with quality assurance anchored to the IAEA-375 reference material. Concentrations measured in parts per million were converted to becquerels per kilogram using standard International Atomic Energy Agency conversion factors. The results showed that uranium-238 activity in soils ranged from 2.11 to 77.38 Bq/kg with a mean of 12.95 Bq/kg, thorium-232 ranged from 8.08 to 66.25 Bq/kg with a mean of 26.87 Bq/kg, and potassium-40 spanned 1.57 to 178.41 Bq/kg with a mean of 39.77 Bq/kg. All three soil averages fell below the UNSCEAR worldwide benchmarks, painting Jebba’s farmland in a comparatively reassuring light.

The stream sediments, however, were a different matter entirely. Uranium-238 in sediments averaged 26.21 Bq/kg, roughly double the soil value, and thorium-232 averaged 109.39 Bq/kg—more than four times the soil mean and well above the international standard limit, with individual samples reaching a remarkable 572.47 Bq/kg. Potassium-40 remained modest at an average of 48.16 Bq/kg. The radium equivalent activity, a composite index that weights the three radionuclides according to their gamma-emission potential, averaged 54.44 Bq/kg in soils but 186.34 Bq/kg in sediments, with a maximum of 926.17 Bq/kg—far beyond the 370 Bq/kg ceiling considered acceptable for construction materials.

The dose metrics reinforce this divide. The average absorbed gamma dose rate was 24.23 nGy/h for soils but 82.05 nGy/h for sediments, against a global outdoor average of 57 nGy/h. The internal hazard index, which captures the respiratory risk from inhaling radon and thoron gases released by building materials, averaged 0.41 for soils—comfortably below the safety threshold of one—but 1.44 for sediments, meaning that if these sediments were quarried and used in home construction, occupants could face meaningful internal exposure. External hazard indices followed the same pattern, with sediments approaching the unity limit at a mean of 0.94 while soils sat at just 0.26.

Perhaps the most consequential finding concerns long-term cancer risk. The excess lifetime cancer risk values ranged from 0.33 to 2.43 for soils but from 0.71 to 18.10 for stream sediments, exceeding UNSCEAR thresholds across both media but dramatically so in the depositional environments. The annual effective dose equivalent for indoor scenarios built on sediment-derived material also surpassed global averages. Organ-specific calculations identified the testes as the most vulnerable tissue, followed by bone marrow, lungs, and ovaries, with total effective dose rates reaching 8.16 mSv per year for sediments compared with 2.30 mSv per year for soils.

Statistical analysis pinpointed the culprit behind these hazards. Pearson correlation matrices revealed that thorium-232 correlated almost perfectly with nearly every radiological index—r values exceeding 0.99 for radium equivalent, hazard indices, and the annual gonadal dose equivalent in sediments—while potassium-40 showed weak correlations below 0.1, reflecting its comparatively low gamma emission. Principal component analysis confirmed the pattern: in soils, the first component explained 90.91 percent of total variance and grouped thorium with all the integrated hazard indices, while uranium and potassium clustered separately. In sediments, the first component accounted for 92.58 percent of variance and pulled thorium, radium equivalent, and the hazard metrics into a single dominant cluster.

The spatial distribution of the radionuclides maps directly onto the region’s geology and hydrology. Uranium activities peaked in the southeastern sector around the Jebba Hills, consistent with weathering of uranium-bearing minerals, while thorium concentrated in the southwestern and northern zones near Shika and the Moga Hills. Potassium-40 showed a gradient toward the south and southwest, reflecting the distribution of feldspar- and mica-rich rocks. Elevated radium equivalent values near the hills suggest geochemical leaching from elevated terrain into surrounding soils, and sediment enrichment around Bajijo and the southern areas points to the decisive role of erosion, transport, and deposition in concentrating fine-grained, radionuclide-bearing particles in stream channels. The authors also note that agricultural practices may contribute: phosphate-based NPK fertilizers, derived from naturally enriched phosphate rocks, can accumulate uranium and thorium in soils through repeated application, while irrigation water carrying dissolved potassium-40 and uranium adds to the radiological load.

Why do sediments outperform soils as radiation reservoirs? The physics and chemistry of sorption provide the answer. Fine-grained particles offer large surface areas and chemically reactive mineral surfaces onto which dissolved radionuclides adsorb readily, promoting their deposition and accumulation in bottom sediments. Once trapped, however, these radionuclides are not permanently immobilized: shifts in pH, redox potential, or organic matter content can remobilize them—under reducing conditions, for instance, uranium can convert to more soluble forms and diffuse back into the water column—while flooding, dredging, and storm events can resuspend contaminated particles and increase their bioavailability. Benthic organisms that ingest contaminated particles can then carry radionuclides into the aquatic food web, opening pathways for bioaccumulation and trophic transfer to humans.

The study’s implications extend beyond Jebba. Across much of West Africa, rural communities routinely draw sand and sediment from streams and riverbeds for building construction, and the finding that Jebba’s sediments exceed internal hazard thresholds sounds a cautionary note for any similar geological setting. The authors recommend continuous monitoring, denser spatial sampling to refine hotspot maps, measurement of additional radionuclides such as cesium-137 and cobalt-60, evaluation of radon emissions from soils and sediments, and the integration of radiological assessments into Nigeria’s national environmental management frameworks. They acknowledge limitations—a single-season snapshot, no epidemiological linkage to actual health outcomes, and limited treatment of hydrodynamic transport—but the core message stands: in this corner of the Niger River basin, thorium-232 is the primary risk driver, and the sediments that quietly collect it in the region’s waterways deserve far closer attention than the ground above them.

Subject of Research: Distribution and radiological health risks of natural radionuclides in soils and stream sediments in Jebba, Nigeria

Article Title: Distribution of 238U, 232Th, and 40K in soils and stream sediments in the Jebba area, Nigeria-an integrated environmental, health and radiological risk assessment

Article References: OlaOlorun, O. A., Popoola, O. J., Oyebamiji, A. O., Abdu‑Raheem, Y. A., & Ukaogo, P. (2025). Distribution of 238U, 232Th, and 40K in soils and stream sediments in the Jebba area, Nigeria-an integrated environmental, health and radiological risk assessment. BMC Environmental Science, 2(1), Article 21. https://doi.org/10.1186/s44329-025-00035-5

Image Credits: AI Generated

DOI: 10.1186/s44329-025-00035-5

Keywords: radionuclides, uranium-238, thorium-232, potassium-40, stream sediments, radiological risk, Nigeria, Jebba, natural radioactivity, cancer risk, soil contamination, environmental health

The research, published in Environmental Geochemistry and Health by a team from Fire University, the Central Laboratory for Radiological Protection and Warsaw University of Technology in Poland, addressed a long-standing blind spot in the assessment of naturally occurring radioactive materials, known as NORM. Most previous studies have treated coal and its combustion residues as independent sample sets, comparing average ash concentrations from power plants with average coal concentrations from mines. That approach obscures the crucial question of whether combustion itself acts as a predictable amplifier of radiological risk. The Polish team instead burned nine hard coals and measured the radioactivity of each ash against its own parent coal, establishing a direct quantitative link between the two.

The nine coals were deliberately chosen for geological diversity. Samples came from the Bowen Basin in Queensland, Australia; the Central Appalachian coalfield in Virginia, United States; the Karaganda and Ekibastuz basins in Kazakhstan; the Moatize Basin in Mozambique; the Cerrejón Formation in Colombia; and two Polish sources, including the Carboniferous Upper Silesian Coal Basin. Together they span depositional ages from the Carboniferous to the Paleogene and represent markedly different tectonic and sedimentary settings. All were collected from shipments transhipped at the Port of Gdansk using a random representative sampling procedure compliant with the ISO 18283:2008 standard, and each was treated as an independent observation of a distinct geological origin.

Measurement relied on gamma-ray spectrometry using a MAZAR analyser coupled to a sodium iodide scintillation probe housed in lead shielding. The activity concentrations of radium-226 and thorium-232 were determined indirectly through their secular equilibrium daughter products, bismuth-214 at 1764 kiloelectronvolts and thallium-208 at 2610 kiloelectronvolts, while potassium-40 was measured directly from its 1460 kiloelectronvolt photopeak. Each crushed and sieved sample was sealed in a 1.7-litre Marinelli vessel and stored for four weeks to allow radioactive equilibrium to be reached before being measured nine times over 18,000-second counting intervals. Combined relative uncertainties typically fell within 10 to 15 percent for radium and thorium and 10 to 12 percent for potassium, with minimum detectable activities of a few becquerels per kilogram.

The combustion stage took place in a Kolton UNIX 20 solid-fuel boiler, a domestic bottom-feed unit operating under natural draught in a fixed-bed grate configuration, with active-zone temperatures typically between 700 and 1050 degrees Celsius. Each coal was burned to completion, the boiler cooled, and the bottom ash carefully collected. The authors acknowledge that domestic grate firing differs from industrial pulverised-coal or fluidised-bed systems in temperature profile, residence time and ash fractionation, but the fundamental mechanism is the same: the organic fraction of coal is oxidised to gas, while mineral-bound radionuclides are retained and concentrated in the solid residue. Notably, fly ash separated in industrial plants often carries even higher radionuclide concentrations than bottom ash, meaning the enrichment factors reported here may be conservative.

In their raw state, all nine coals proved radiologically unremarkable. Activity concentrations of radium-226, thorium-232 and potassium-40 sat below global average values for hard coal and for the Earth’s crust, with the lowest readings in the Colombian sample and the highest radium and thorium values in the Mozambican coal. The Polish Upper Silesian sample contained the most potassium-40. None of the coals exceeded any of the standard radiological screening indices: radium equivalent activity ranged from 19.3 to 57.7 becquerels per kilogram, far below the 370 becquerel per kilogram safety threshold, external hazard indices stayed well under unity, and gamma dose rates of 1.74 to 25.90 nanogray per hour remained below both the global average of 54 nanogray per hour and the Polish average of 47.4. As fuels, these coals posed negligible radiological concern.

Combustion changed the picture dramatically. Enrichment factors relating ash activity to coal activity ranged from approximately 3.8 to 9.9, clustering around a median of about six for every radionuclide and every derived hazard index. A paired Wilcoxon signed-rank test confirmed the increase was statistically robust, with a very large effect size of r = 0.889 and complete directional consistency: in all nine coal-ash pairs, every measured parameter rose. The mechanism is essentially a mass-balance effect. When the organic matter burns away, the ash yield drops to an estimated 10 to 27 percent of the original coal mass, so the same absolute quantity of radionuclides is packed into a much smaller mass. Earlier studies had reported enrichment factors of two to five; the tighter, higher and more uniform amplification observed here likely reflects the paired experimental design, which excludes the confounding effects of fuel blending and heterogeneous ash streams in large power stations.

The radiological consequences of this amplification were visible in every index calculated for the ash. Radium equivalent activity in the ashes ranged from 149 to 418 becquerels per kilogram, external hazard indices from 0.46 to 1.13, gamma dose rates from 68 to 185 nanogray per hour, annual effective doses from 0.018 to 0.226 millisieverts per year, and the radioactivity concentration index from 0.52 to 1.46. The most radioactive ash, derived from the Mozambican coal, exceeded regulatory thresholds across multiple parameters. Critically, the external gamma dose rate surpassed the recommended reference level of 54 nanogray per hour in all nine ash samples, even though most other indices remained within limits. The authors stress that the study assessed the potential for environmental impact based on the elevated activity of the ash itself, not on direct observation of radionuclide migration into soil, water or air.

Why does this matter beyond the laboratory? Coal ash is one of the most heavily reused industrial by-products on Earth, finding its way into concrete, road base layers, land reclamation schemes and even, occasionally, agricultural applications mixed with sewage sludge. Each of these uses creates a potential pathway for concentrated NORM to disperse into soil, groundwater and the built environment. The difference between a two- or three-fold enrichment and a six-fold one is far from trivial when millions of tonnes of residue are involved, and the authors argue that risk assessments based on average literature ash values may systematically underestimate exposure if coal-specific transformation factors are ignored. Under the Euratom Basic Safety Standards, which set activity concentration reference levels for building materials, some combustion residues may fall within regulatory scope when used in construction.

The study’s conclusions come with honest caveats. Nine coal-ash pairs, while sufficient for the non-parametric statistical framework applied, cannot capture the full global variability of coal composition, and a single prepared sample per pair means the reported uncertainties reflect counting statistics rather than within-material heterogeneity. The domestic boiler used cannot reproduce industrial combustion conditions exactly. Yet the central message stands with unusual statistical clarity: combustion acts as a proportional and predictable amplifier of natural radioactivity, so the radiological properties of an ash can be inferred from its parent coal. As Poland and other nations continue importing coals from geologically diverse basins while promoting circular-economy reuse of combustion residues, the authors call for continuous monitoring of both domestic and imported coal, and for transformation processes to be built into environmental risk assessment frameworks. A material that enters the furnace radiologically harmless may not leave it that way.

Subject of Research: Radionuclide enrichment and radiological hazard transformation during coal combustion

Article Title: Radiological characteristics of coal-to-ash transformation: a paired coal-ash assessment of natural radionuclides

Article References: Łukaszek-Chmielewska, A., Rachwał, M., Rakowska, J., Piotrowska, B., Isajenko, K., & Szyłak-Szydłowski, M. (2026). Radiological characteristics of coal-to-ash transformation: a paired coal-ash assessment of natural radionuclides. Environmental Geochemistry and Health, 48(15), Article 612. https://doi.org/10.1007/s10653-026-03509-w

Image Credits: AI Generated

DOI: 10.1007/s10653-026-03509-w

Keywords: coal ash, NORM, radionuclides, gamma-ray spectrometry, radiological hazard, TENORM, bottom ash, coal combustion, environmental radioactivity, radium-226, thorium-232, potassium-40

The research, published in the journal Environmental Geochemistry and Health, was conducted by a team from PES College of Engineering in Mandya, ATME College of Engineering in Mysuru and Visvesvaraya Technological University in Belagavi. The researchers collected soil samples from twenty-one quarry sites scattered across the district, a region whose geology is dominated by granitic terrain. Granite is chemically notorious among radiation scientists: it tends to be enriched in the minerals that carry uranium-series and thorium-series isotopes as well as potassium-40, so soils weathered from granitic bedrock typically register activity concentrations well above the global averages for ordinary soils. This geological signature is precisely what the team’s measurements captured.

Quantifying trace radioactivity requires a sensitive analytical instrument, and the study relied on high-purity germanium (HPGe) gamma-ray spectrometry, the workhorse technique of environmental radiometry. HPGe detectors, when cryogenically cooled, resolve the characteristic gamma-ray energies emitted by each decay chain with exquisite precision, allowing researchers to identify individual radionuclides within a mixed sample. By measuring the intensity of gamma lines characteristic of radium-226, thorium-232 and potassium-40, the team computed the activity concentrations of each isotope in becquerels per kilogram — a measure of how many atomic disintegrations occur per second in each kilogram of soil. The mean values they reported were 39.5 Bq/kg for radium-226, 81.5 Bq/kg for thorium-232 and 656 Bq/kg for potassium-40, confirming the influence of the granitic geology, particularly the elevated thorium and potassium content.

These individual numbers become far more informative when combined into composite indices that radiation protection agencies have designed to summarise risk. The researchers calculated the radium equivalent activity, Ra_eq, which weights the three radionuclides according to their respective gamma contributions; it averaged 206.5 Bq/kg, below the widely used ceiling of 370 Bq/kg associated with a dose of 1 mSv per year. They also computed the gamma radiation representative index (Iγr), the external hazard index (Hex) and the internal hazard index (Hin), which came out at averages of 1.52, 0.56 and 0.66 respectively. The two hazard indices both sit below unity, the conventional threshold indicating that the materials would pose no unacceptable radiological risk if used in construction, either outdoors where exposure is external or indoors where radon inhalation and gamma irradiation combine.

The ratios between the three radionuclides tell their own geological story. The team reported average activity concentration ratios of 2.05 for thorium-232 to radium-226, 16.65 for potassium-40 to radium-226 and 8.15 for potassium-40 to thorium-232. A thorium-to-radium ratio above two is characteristic of soils derived from rocks in which thorium-bearing minerals such as monazite accumulate preferentially, a hallmark of many Indian granitic terrains. Such ratios serve as fingerprints that connect surface soil measurements to the deeper petrology of the region, and they help distinguish natural geological enrichment from any anthropogenic contamination, which was not indicated at these sites.

Laboratory spectrometry alone does not capture the full radiological picture, because real-world exposure happens in situ, under open skies and variable conditions. To complement the sample analysis, the team deployed a calibrated ER-709 portable dosimeter at the quarry locations to measure ambient gamma radiation directly. The instrument recorded an average absorbed gamma dose rate of 89.06 nanogray per hour. Converting this absorbed dose into a quantity that health physicists can compare against international exposure standards yields an annual effective dose of approximately 0.11 millisieverts per year — a figure far below the roughly 2.4 millisieverts per year that every human being receives on average from all natural sources, including cosmic rays, food and inhaled radon.

From the dose measurements the researchers extrapolated two widely used risk metrics. The excess lifetime cancer risk, a statistical estimate of the additional lifetime cancer probability attributable to the measured exposure, averaged 0.38 × 10⁻³, meaning an additional cancer risk of roughly one in twenty-six hundred — within the range that international bodies such as the World Health Organization and the International Commission on Radiological Protection consider acceptable for natural background exposure. The team also estimated an annual gonadal dose equivalent of 671.22 microsieverts per year, a quantity relevant to hereditary effects because gonadal tissues are among the most radiation-sensitive in the body. Again, this value remained within the range documented for ordinary terrestrial environments worldwide and did not approach levels of concern.

The findings carry practical significance beyond academic interest. India’s construction industry consumes enormous quantities of crushed granite aggregate, dimension stone and quarry dust, and regulators must decide whether quarry-derived materials can be used safely in dwellings, schools and infrastructure. The study’s hazard indices below unity provide direct evidence that, for the sites examined in Mandya district, these materials do not exceed radiological constraints for building use. Equally important, the work establishes a baseline: because natural radioactivity varies with geology, long-term monitoring programmes need reference data to detect future changes, whether caused by new excavation, land-use shifts or industrial inputs. The authors emphasise that the dataset provides exactly such a foundation for future soil radioactivity monitoring and radiological assessments in the region.

The Mandya results also sit within a growing body of Indian and international literature on naturally occurring radioactive materials. Comparable surveys of granite quarries in the Bangalore rural district of Karnataka, of soils in neighbouring districts and of quarry sites in states such as Tamil Nadu, Punjab and Kerala have documented similar patterns of granitic enrichment, with regional variations driven by local mineralogy. Globally, studies from Egypt, Turkey, Brazil, Bangladesh, Nigeria and China have applied the same battery of indices — Ra_eq, Hex, Hin, Iγr and excess lifetime cancer risk — to quarry soils, building stones and beach sands, creating a common framework for comparing radiological safety across continents. Against that backdrop, Mandya’s quarry soils emerge as geologically distinctive but radiologically unremarkable.

For the workers and residents of Mandya district, the practical message of the study is one of reassurance grounded in careful measurement rather than assumption. Natural radioactivity is inescapable — it emanates from the bedrock beneath our feet, the minerals in our building materials and even the potassium in our own cells — and the relevant question is always whether local levels exceed the thresholds that decades of radiobiological research have established. In this corner of southern India, where ancient granites meet one of the world’s busiest quarrying economies, the answer is a measured no. The radiation written into the stone is real, quantifiable and now well documented, but it remains a modest contributor to the background radiation that all life on Earth has always lived with.

Subject of Research: Assessment of natural radioactivity from radium-226, thorium-232 and potassium-40 in quarry soils of Mandya district, Karnataka, India

Article Title: Assessment of 226Ra, 232Th and 40K in soil with gamma dose rates from quarries of the Mandya district, Karnataka, India

Article References: Nagaraju, R. M., Siddaiah, S. T., Dudda, C., Halligudra, G., & Jayaram, A. K. (2026). Assessment of 226Ra, 232Th and 40K in soil with gamma dose rates from quarries of the Mandya district, Karnataka, India. Environmental Geochemistry and Health, 48(15), Article 598. https://doi.org/10.1007/s10653-026-03470-8

Image Credits: AI Generated

DOI: 10.1007/s10653-026-03470-8

Keywords: natural radioactivity, radium-226, thorium-232, potassium-40, gamma-ray spectrometry, HPGe detector, quarry soils, granite, radiation dose, radiological hazard assessment, Karnataka, environmental radioactivity

The team used gamma-ray spectroscopy with a sodium iodide detector coupled to a multichannel analyser, calibrating the system with traceable reference sources to identify the characteristic energy peaks of potassium-40, uranium-238 and thorium-232. Samples were collected in acid-rinsed containers, treated with concentrated hydrochloric acid to fix the radioactive elements, and stored for four weeks to allow secular equilibrium between the parent radionuclides and their decay products before counting. Background radiation was characterised by counting an empty container for 36,000 seconds, and minimum detectable activities were calculated for each radionuclide to ensure the measurements were statistically meaningful rather than noise.

The results show a consistent pattern of elevated radioactivity. In Benin City, mean activity concentrations were 56.1 plus or minus 1.5 becquerels per litre for potassium-40, 4.3 plus or minus 0.8 becquerels per litre for uranium-238 and 9.3 plus or minus 1.5 becquerels per litre for thorium-232. In Ogwa, potassium-40 averaged even higher at 67.3 plus or minus 1.8 becquerels per litre, while uranium-238 and thorium-232 averaged 2.5 and 6.9 becquerels per litre respectively. Against guideline values of roughly 10, 10 and 1.0 becquerels per litre for these three radionuclides, potassium-40 and thorium-232 were clearly out of bounds, with about ninety-three percent of samples exceeding the safe limits for those isotopes. The highest potassium-40 reading in Benin City reached 132.6 becquerels per litre, while uranium-238 remained within acceptable limits everywhere except two locations.

Dose calculations converted these activity concentrations into annual effective doses using standard ingestion coefficients and age-specific water intake rates for six age categories: infants, one-year-olds, five-year-olds, ten-year-olds, fifteen-year-olds and adults. In Benin City, mean annual effective doses ranged from 3.7 millisieverts per year for infants down to 1.3 millisieverts per year for ten-year-olds, while Ogwa produced values between 3.0 and 1.1 millisieverts per year. Every mean value in every age group exceeded the World Health Organization’s tolerable limit of 0.1 millisieverts per year by more than an order of magnitude, and infants emerged as the most vulnerable group because of their comparatively high water intake per unit body mass.

Thorium-232 proved to be the dominant contributor to the total dose, accounting for roughly eighty-one percent of the annual effective dose for infants in Benin City and nearly eighty percent for adults, followed by potassium-40 and finally uranium-238. This ordering matters because the dose conversion factor for ingested thorium is several times higher than for uranium or potassium, meaning even moderate thorium levels translate into disproportionately large effective doses. The researchers attribute the thorium enrichment to the local geology: the region sits atop the Benin Formation, a sedimentary sequence rich in heavy minerals such as monazite and zircon that host thorium in their crystal lattices. Unlike uranium, which migrates readily as soluble U(VI), thorium exists as highly insoluble Th(IV) and reaches groundwater mainly through colloid-mediated transport of fine particles and alpha recoil during prolonged water-rock interaction.

The study also computed a suite of radiological hazard indices. Radium equivalent activity averaged 21.9 becquerels per litre in Benin City and 17.5 in Ogwa, well below the recommended ceiling of 370 becquerels per litre, and the external and internal hazard indices and the representative gamma index all remained far below unity. The annual gonadal equivalent dose averaged 69.7 and 57.6 for the two locations respectively, beneath the standard reference value. In other words, the acute external hazard posed by the water is modest. The concern centres instead on chronic ingestion: the excess lifetime cancer risk exceeded the global mean of 0.2 times ten to the minus three at every sampling point. Mean ELCR values in Benin City reached 10.0 times ten to the minus three per year for infants and 5.3 for adults, while Ogwa’s values, though lower, remained above the safe benchmark.

One of the most striking findings lies in the statistical structure of the data. In Benin City, all radionuclides and hazard indices showed strong positive correlations, statistically significant at the one percent level, with coefficients approaching one for pairs such as radium equivalent and absorbed dose rate. The researchers interpret this as the signature of a homogeneous hydrogeochemical regime in the sedimentary coastal plain aquifer, where high infiltration rates and uniform leaching move the radionuclides together. Ogwa told a different story. Sitting on the fractured Precambrian Basement Complex of the Esan Plateau, the town’s aquifer produced a negative correlation of minus 0.79 between potassium-40 and thorium-232, and potassium-40 correlated negatively with nearly every hazard index. This suggests that thorium and uranium, locked in accessory minerals like zircon and monazite, follow entirely different mobilisation pathways from potassium released by weathering feldspars, and that agricultural fertiliser use may further elevate potassium levels in the rural setting.

Comparisons with international studies place the Edo State values in an intermediate to high range. Uranium concentrations here fall below those reported for crystalline basement regions of Kwara State and Abuja but exceed levels found in Ghana, Burkina Faso, Brazil, Malaysia, Serbia and Spain. Thorium levels are far above the 1.0 becquerel per litre benchmark and comparable to values in Iraq, Pakistan, Bangladesh and Kenya. Perhaps most tellingly, the estimated ingestion doses for adults, between 1.6 and 2.0 millisieverts per year, exceed exposure pathways usually considered dominant in Nigeria, including seafood consumption in petroleum-impacted Niger Delta communities, indoor exposure near petroleum facilities, vegetable intake in Ilorin and even doses received by artisanal gold miners. Untreated groundwater from thorium-enriched formations, the authors conclude, represents a greater cancer burden than industrial pollution or mining occupations in the populations studied.

The researchers acknowledge that the imbalance between thirty samples from Benin City and only four from Ogwa limits statistical power for the rural site, and they frame the Ogwa findings as preliminary. Nevertheless, they argue the case for action is urgent. They recommend continuous radiological monitoring of borehole water, household-level mitigation using reverse osmosis, activated alumina or ion-exchange systems capable of removing more than ninety-five percent of radionuclides, and the integration of radiological screening into borehole registration and drinking water certification by regulatory bodies such as NAFDAC and the Edo State Ministry of Environment. Future work, they suggest, should examine seasonal variation linked to rainfall and recharge, food chain transfer of the isotopes into crops, and epidemiological studies of cancer incidence among dependent populations. For now, the message for the roughly 1.8 million residents of Benin City and the communities of Esan Land is clear: the aquifer beneath their feet is quietly radioactive, and the water drawn from it deserves systematic scrutiny before long-term exposure turns a geological fingerprint into a public health crisis.

Subject of Research: Natural radionuclide contamination and radiological health risks in borehole drinking water in Benin City and Ogwa, Edo State, Nigeria

Article Title: Assessment of natural radionuclides and radiation hazard indices of borehole water samples collected from selected locations in Benin City and Ogwa, Edo State, Nigeria

Article References: Popoola, F. A., & Osahon, O. D. (2026). Assessment of natural radionuclides and radiation hazard indices of borehole water samples collected from selected locations in Benin City and Ogwa, Edo State, Nigeria. BMC Environmental Science, 3(1), Article 14. https://doi.org/10.1186/s44329-026-00057-7

Image Credits: AI Generated

DOI: 10.1186/s44329-026-00057-7

Keywords: radionuclides, borehole water, groundwater, radiation hazard, thorium-232, potassium-40, uranium-238, annual effective dose, excess lifetime cancer risk, gamma-ray spectroscopy, Benin City, Nigeria

The team, led by Xuan-Quang Nguyen of Dong Nai Technology University and Trung-Tien Chu of VNU School of Interdisciplinary Sciences and Arts, together with Van-Hao Duong and Thanh-Xuan Pham-Thi, found striking differences between the isotopes. Potassium-40 dominated every sample by a wide margin, with mean activity concentrations of 101 plus or minus 8.6 becquerels per kilogram, ranging from 65 to 169 becquerels per kilogram. This was expected, since potassium is an essential element that fish regulate biologically regardless of environmental conditions, and its radioactive isotope makes up a fixed fraction of all natural potassium. Polonium-210 followed at 11.8 plus or minus 0.9 becquerels per kilogram, lead-210 at 9.1 plus or minus 1.7, radium-226 at 7.69 plus or minus 1.04, and radium-228 at just 1.22 plus or minus 0.2 becquerels per kilogram, with some measurements falling below detection limits.

These differences are not random. Each radionuclide behaves according to its own chemistry in aquatic systems. Polonium-210, a highly radiotoxic alpha emitter from the uranium-238 decay chain, is known to bind strongly to proteins and organic matter, making it particularly prone to bioaccumulation in fish tissue. Lead-210, its precursor in the same decay chain, behaves differently, attaching to particles and sediments. Radium isotopes, chemical analogs of calcium, tend to concentrate in bone and calcified structures. Potassium-40, as an essential element analog, is homeostatically controlled. The Red River itself carries a heavy sediment load shaped by decades of dam construction and land-use change in its watershed, and earlier work by some of the same authors documented elevated natural radioactivity in the river’s surface sediments, providing a plausible source term for the isotopes measured in fish.

One of the most intriguing findings concerns fish biology. The researchers observed a negative correlation between radium-226 concentrations and body weight, suggesting that smaller fish accumulate proportionally more of this isotope than larger individuals. This morphological influence on radioactivity absorption has practical implications for monitoring programs, which often assume that radionuclide concentrations scale simply with size or trophic position. If body weight systematically modulates uptake, then sampling strategies that ignore biological characteristics could misestimate the radiological burden carried by a fish population, and by extension the dose delivered to human consumers who prefer particular size classes.

To translate these measurements into human health terms, the team calculated annual effective doses from fish consumption. The average annual effective dose came to 0.105 millisieverts per year, with individual values ranging from 0.030 to 0.247 millisieverts per year. These figures sit comfortably below internationally recognized safety thresholds, which typically allow on the order of 1 millisievert per year of additional exposure from all practices combined. Lifetime cancer risk estimates ranged from 1.4 times ten to the minus seven to 7.7 times ten to the minus seven, well within the acceptable limits used by radiological protection agencies worldwide. In plain terms, an ordinary consumer of Red River fish faces a negligible incremental cancer risk from natural radioactivity in the fish they eat.

The story is more nuanced for the fish themselves. Using the ERICA Tool, a widely adopted software framework for assessing ionizing radiation doses to wildlife, the researchers estimated total dose rates to the fish ranging from 0.2 to 10.4 micrograys per hour, with a mean of 3.0 micrograys per hour. Most species fell well below the screening threshold of 10 micrograys per hour, indicating negligible ecological risk. But one species, the Zig-zag eel, exceeded that threshold, signaling a potential radiological concern for this species specifically. The result highlights that ecological risk from natural radionuclides is not distributed evenly across a food web; species-specific feeding habits, habitat use, and physiology can push individual species over protective screening levels even when the community as a whole appears safe.

The Zig-zag eel finding deserves careful interpretation. Screening thresholds in tools like ERICA are deliberately conservative, designed to flag cases that warrant more detailed investigation rather than to declare harm definitively. Exceeding the threshold does not mean the eel population is being damaged, but it does mean the species merits closer study, including tissue-specific dose modeling and, ideally, biological endpoints such as reproductive success. For a river basin that supports intensive fishing and aquaculture, identifying which species sit closest to ecological limits is a valuable early-warning capability.

The study also fills an important regional data gap. Vietnam’s Red River basin is home to tens of millions of people, and fish from the river and its delta contribute substantially to local protein intake. Yet systematic measurements of natural radionuclides in the basin’s freshwater biota have been scarce, with prior work focusing mainly on sediments, soils, and thermal waters. By establishing baseline activity concentrations across ten commercially and nutritionally important species, the researchers have created a reference point against which future changes, whether from industrial development, mining activity in the geologically radioactive highlands upstream, or shifts in sediment dynamics caused by dams, can be detected and evaluated.

Methodologically, the work demonstrates the value of combining direct radiometric measurement with biological covariates and dual risk frameworks, one for humans and one for wildlife. The inter-isotope variability observed, spanning nearly two orders of magnitude between radium-228 and potassium-40, underscores why single-isotope assessments can be misleading. Polonium-210, for example, typically contributes the dominant share of internal dose from fish consumption even when potassium-40 dominates total activity, because polonium’s alpha radiation carries far higher radiotoxicity per unit of activity. Comprehensive multi-isotope datasets like this one allow risk assessors to weight each nuclide appropriately rather than relying on activity totals alone.

For the public, the bottom line is reassuring: eating fish from the Red River does not pose a meaningful radiological health risk under current conditions. For scientists and regulators, the study offers something equally valuable, a rigorous baseline and a demonstration that fish biology matters in radiological monitoring. As radiation monitoring programs expand across Southeast Asia’s river systems, the Red River work suggests that the most informative datasets will be those that record not just what is in the water and sediment, but how the size, species, and ecology of the fish themselves shape the journey of natural radioactivity through the food web.

Subject of Research: Natural radionuclide accumulation in freshwater fish from the Red River, Vietnam, and its implications for human and ecological radiological risk

Article Title: Natural Radionuclides in Selected Freshwater Fishes from the Red River (Vietnam): Influence of Biological Characteristic and Implication for Human Health Risk

Article References: Nguyen, X.-Q., Duong, V.-H., Pham-Thi, T.-X., & Chu, T.-T. (2026). Natural Radionuclides in Selected Freshwater Fishes from the Red River (Vietnam): Influence of Biological Characteristic and Implication for Human Health Risk. Archives of Environmental Contamination and Toxicology, 91(2), Article 17. https://doi.org/10.1007/s00244-026-01217-1

Image Credits: AI Generated

DOI: 10.1007/s00244-026-01217-1

Keywords: natural radionuclides, Red River Vietnam, freshwater fish, polonium-210, potassium-40, radium-226, radiological risk assessment, ERICA Tool, food safety, annual effective dose, Zig-zag eel, radiation monitoring