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 radionuclides at the center of the investigation, radium-226 and radium-228, are decay products of the uranium-238 and thorium-232 series that occur naturally in the Earth’s crust. They matter for drinking water because of their chemistry and their biology. Radium is relatively soluble compared with its parent elements, so it leaches readily from minerals into groundwater. Its two isotopes have half-lives long enough to persist in aquifers, 1,600 years for radium-226 and 5.75 years for radium-228, and once ingested the body treats radium much like calcium, depositing it in bone. There, the alpha and beta radiation emitted by the isotopes and their short-lived progeny can irradiate bone tissue, a pathway historically linked to elevated risks of bone cancer and other malignancies. The WHO sets guidance levels of 1.0 becquerel per liter for radium-226 and 0.1 becquerel per liter for radium-228, values designed so that lifetime consumption at those levels would deliver an annual committed effective dose of roughly 0.1 millisieverts.

The analytical backbone of the study was high-purity germanium gamma spectrometry performed at the Radiation Protection Institute in Accra. One-liter samples were sealed in Marinelli beakers and stored for three to four weeks, allowing radium-226 to reach secular equilibrium with its short-lived progeny lead-214 and bismuth-214, and radium-228 to equilibrate with actinium-228. The detector, an N-type HPGe with 25 percent relative efficiency and a resolution of 1.8 kiloelectronvolts at 1332 kiloelectronvolts, was calibrated with a mixed radionuclide standard in identical geometry, and each sample was counted for a demanding 36,000 seconds, ten full hours, to push detection limits as low as possible. Radon-226 was quantified through the 609.3 and 351.9 kiloelectronvolt lines of its progeny, while radium-228 was measured through actinium-228 gamma lines at 911.2 and 968.9 kiloelectronvolts. Even so, the minimum detectable activities were 0.12 becquerels per liter for radium-226 and 0.14 becquerels per liter for radium-228.

That second detection limit turns out to be one of the study’s most consequential technical findings. Because the detection limit for radium-228, 0.14 becquerels per liter, sits above the WHO guidance level of 0.1 becquerels per liter, a non-detect cannot demonstrate compliance. Every sachet and tap water sample in the study, across all three regions and both seasons, returned results below the detection limits for both isotopes. For radium-226, whose detection limit is an order of magnitude below its guidance level, that genuinely establishes compliance. For radium-228, the honest reading is more cautious: the true activity could lie anywhere between zero and 0.14 becquerels per liter, a range that spans the guideline. Treating both detection limits as upper bounds yields a screening dose of 0.095 millisieverts per year, which falls just below, but not comfortably below, the WHO individual dose criterion of 0.1 millisieverts per year. The margin is roughly 5 percent, smaller than the analytical uncertainty of the measurement itself.

The untreated sources told a dramatically different story. Borehole water, the primary drinking supply for peri-urban and rural communities without piped infrastructure, contained 5.03 to 5.16 becquerels per liter of radium-226 and 5.06 to 5.34 becquerels per liter of radium-228, exceeding the WHO guidance levels by factors of roughly five and about 51 to 53 respectively. River water was higher still. Samples from the Densu, Kakum, Pra and Anankwar rivers, along with the Weija and Kpong reservoirs, registered 27.02 to 28.39 becquerels per liter of radium-226 and 29.01 to 30.09 becquerels per liter of radium-228, overshooting the guidance levels by factors of roughly 27 to 28 and 290 to 301. These river values are unusually high for surface water anywhere in the world, and the authors themselves flag that they require independent confirmation before being used for regulatory decisions.

Converting activity into dose, the researchers applied standard ingestion dose coefficients, 2.8 times ten to the minus four millisieverts per becquerel for radium-226 and 6.9 times ten to the minus four for radium-228, multiplied by an assumed consumption of two liters per day, or 730 liters per year. Under the deliberately conservative assumption that an adult drinks exclusively from a single source for an entire year, borehole water delivered a screening dose of 3.58 to 3.73 millisieverts per year, roughly 36 times the WHO criterion, while river water delivered 20.14 to 20.96 millisieverts per year, about 200 times that benchmark and twenty times the 1 millisievert per year reference level of the International Basic Safety Standards. Notably, radium-228 contributed about 70 percent of the total dose in both cases despite similar activity concentrations, because its dose coefficient is roughly 2.5 times larger. The authors stress these are screening values, not measured exposures; anyone who switches between sources would receive less, and no age-resolved estimates were made for children, infants or pregnant women.

Season emerged as a meaningful variable. Wet-season activities exceeded dry-season values in every untreated source and region, with average increases of 1.8 to 4.9 percent. Statistical testing by one-way analysis of variance confirmed the seasonal effect was significant for borehole radium-228, river radium-226 and river radium-228, though not for borehole radium-226. The pattern is consistent with enhanced mineral dissolution, groundwater recharge and catchment runoff during the rains, which mobilize radionuclides from aquifer and catchment materials. Equally telling was what the regional comparison did not find: combined radium activities in river water were nearly identical across the three regions, 57.22, 57.26 and 57.24 becquerels per liter, with no statistically significant differences. The dataset therefore provides no basis for attributing regional variation to differences in underlying geology.

What explains the elevated activities in the untreated sources? The coastal belt is underlain by Precambrian crystalline rocks, Birimian metavolcanics, Tarkwaian sediments and coastal sedimentary basins, all of which host uranium- and thorium-bearing accessory minerals such as monazite, zircon and apatite. Weathering, dissolution and alpha-recoil release of radium from these minerals is the most plausible geogenic source, and the catchments of the Kakum, Pra and Anankwar rivers also host extensive artisanal gold mining that disturbs mineralized material and inflates suspended sediment loads. But the authors are careful: the study measured no hydrogeochemical parameters, performed no mineralogical characterization and conducted no source apportionment, so a geogenic origin remains a hypothesis rather than a demonstrated conclusion. A further technical caveat concerns the river samples themselves. They were collected as unfiltered whole-water samples and acidified to below pH 2, a procedure that leaches radium from suspended particles into solution. The reported values therefore represent total radium, dissolved plus particulate-bound, and likely overstate what a consumer actually absorbs.

The authors are equally explicit about what the exceedances do and do not mean. WHO guidance levels are conservative operational screening criteria, not thresholds of harm, and the 1 millisievert reference level is a trigger for planning protective action rather than a dose limit. The findings, they argue, call for confirmatory sampling by independent laboratories, source-specific investigation, and consideration of treatment, not a declaration of health detriment. Proven radium removal technologies exist, including ion exchange, reverse osmosis, activated alumina and lime softening, and the burden of exposure falls disproportionately on communities with the fewest alternatives to boreholes and rivers. The study also carries a regulatory message: Ghana’s national drinking water standards do not mandate routine radiological testing, and any future monitoring program must specify methods sensitive enough to detect activities below the guidance level, since a method whose detection limit exceeds the criterion cannot demonstrate compliance no matter how many samples are analyzed.

As a piece of baseline science, the work fills a genuine gap. Previous Ghanaian studies focused on mining-impacted areas or single municipalities and reported borehole radium-226 at or below 1 becquerel per liter, far lower than the values found here, which sit at or above the upper end of ranges typical of crystalline-basement aquifers worldwide. The recommended follow-up is concrete: paired raw and treated samples to quantify treatment removal, parallel filtered and unfiltered river sampling to separate dissolved from particulate radium, hydrogeochemical and mineralogical work to test the geogenic hypothesis, and an age-resolved dose assessment grounded in an actual consumption survey. Until then, the image that lingers is one of contrast, of city dwellers sipping radiologically quiet sachet water while, a few kilometers away, families draw water from boreholes and rivers that geology has quietly loaded with radium.

Subject of Research: Naturally occurring radium-226 and radium-228 contamination in drinking water sources along Ghana's coastal regions

Article Title: Assessment of 226Ra and 228Ra activity concentrations in drinking water sources along Ghana’s coastal communities

Article References: Agyeman, B. K., Adukpo, O. K., Adotey, D. K., & Serfor-Armah, Y. (2026). Assessment of 226Ra and 228Ra activity concentrations in drinking water sources along Ghana’s coastal communities. Discover Geoscience, 4(1), Article 397. https://doi.org/10.1007/s44288-026-00765-2

Image Credits: AI Generated

DOI: 10.1007/s44288-026-00765-2

Keywords: radium-226, radium-228, drinking water, Ghana, gamma spectrometry, WHO guidance levels, groundwater, natural radioactivity, radiological assessment, borehole water, river water, public health

Natural radioactivity is everywhere in the Earth’s crust, and marine sediments are no exception. The decay chains of uranium-238 and thorium-232, together with the primordial isotope potassium-40, emit gamma radiation continuously, and the dose a beachgoer receives depends on the mineral makeup of the grains underfoot. Granitic catchments, black sands rich in heavy minerals, and phosphate-bearing deposits can all push local dose rates well above the world average, which is why coastal radiological surveys have become a standard tool of environmental protection. The Red Sea is a particularly interesting candidate for such a survey because its flanking mountains are largely Precambrian basement rocks, granites and ophiolites that can carry elevated concentrations of uranium and thorium, and because the region’s rapid coastal development has raised questions about what exactly is accumulating in the sediment.

To answer those questions, the researchers collected twenty-six samples of coastal sediment and subjected them to two complementary analytical techniques. Gamma-ray spectrometry, using high-resolution detectors, allowed them to quantify the specific activity concentrations of uranium-238, thorium-232 and potassium-40 in becquerels per kilogram, a measure of how many radioactive decays occur per second in each kilogram of material. Inductively coupled plasma mass spectrometry, or ICP-MS, then provided elemental fingerprints, measuring major oxides and a suite of potentially toxic metals including lead, cadmium, zinc, copper, rubidium, bromine, cobalt and nickel with parts-per-billion sensitivity. This pairing is powerful because radioactivity and chemistry tell different parts of the same story: the radionuclides reveal the contribution of detrital minerals from the hinterland, while the metal suite captures both geogenic background and any anthropogenic inputs from ports, industry and urban runoff.

The radiological results are strikingly low. Uranium-238 activities ranged from 5 to 38 becquerels per kilogram, thorium-232 from essentially zero to 13 becquerels per kilogram, and potassium-40 from 22 to 501 becquerels per kilogram. Every one of these ranges falls below the worldwide average values reported for soils and sediments by the United Nations Scientific Committee on the Effects of Atomic Radiation. In practical terms, the Red Sea shoreline is one of the quieter natural radiation environments a person could stand on. The team converted these activity concentrations into the standard battery of hazard indices used by radiation protection authorities, and each one told the same story.

The most important of these indices is the radium equivalent activity, a weighted combination of the three radionuclides that accounts for their differing gamma energies and their relative contributions to external dose. For the Red Sea sediments, radium equivalent activity ranged from 31 to 82 becquerels per kilogram, far below the internationally recognized safety limit of 370 becquerels per kilogram. The external and internal hazard indices, which must remain below unity to indicate acceptable risk, were both well under 1 at every sampling site. The absorbed gamma dose rate in air, calculated from the activity concentrations, came out between 15 and 40 nanogray per hour, and the corresponding annual effective dose to a member of the public ranged from 0.04 to 0.06 millisieverts per year. For comparison, the global average outdoor external dose from terrestrial gamma radiation is roughly 0.07 millisieverts per year, meaning a year spent on these beaches delivers less radiation than a couple of chest X-rays and considerably less than a single transcontinental flight.

Radioactivity, however, is only half of the environmental ledger. The ICP-MS measurements revealed a clear hierarchy of metal abundance in the sediments, with strontium leading the list, followed by barium, chromium, bromine, vanadium, zirconium, zinc, nickel, rubidium, copper, cobalt, lead, uranium and thorium. This ordering is itself diagnostic. Strontium and barium are characteristic of carbonate-rich marine sediments and evaporitic influences, while chromium, vanadium and nickel can trace mafic and ultramafic source rocks, the ophiolitic fragments of oceanic crust that were thrust onto the Red Sea margins during the opening of the basin. The prominence of bromine points to organic-rich fractions and biological activity in the coastal zone. The relatively low positions of lead and cadmium in the abundance sequence suggest that industrial contamination, where present, is not dominating the geochemical signature.

To untangle the sources of these elements, the team applied principal component analysis, a multivariate statistical technique that compresses many correlated variables into a few independent axes. PCA is the workhorse of environmental geochemistry because it can reveal whether elements travel together, a strong hint that they share a common origin. Elements released by the weathering of the same bedrock tend to cluster on the same component, whereas pollutants introduced by a specific human activity form their own pattern. The analysis of the geochemical and radiological datasets allowed the researchers to identify the potential sources of the metals and radioactive isotopes and to map the correlations and spatial patterns across the coastline, confirming that lithology and mineral composition, rather than pollution, are the primary controls on the observed variability.

The most unusual ingredient in this study, and the one that elevates it above a conventional sediment survey, is the integration of geophysical data. The researchers analyzed Bouguer gravity anomalies, measurements of tiny variations in the Earth’s gravitational field caused by differences in rock density below the surface. By separating the gravity field into regional and residual components, they could distinguish the signatures of deep crustal structures from those of shallow density contrasts. The interpretation highlighted a northwest to southeast structural grain as the dominant influence on the region’s geology, a direction that mirrors the axis of the Red Sea rift itself, with east to west and northeast to southwest trends playing subordinate roles. This matters for the sediment study because those deep-seated fault systems control where wadis discharge sediment, where basement rocks of different composition crop out, and ultimately why radioactivity and metal concentrations vary from one stretch of coast to the next. Density contrasts inferred from the gravity data supported the interpretation of the spatial variability seen in the chemical measurements, tying the surface geochemistry to the subsurface architecture in a single coherent picture.

The authors are careful to note that safety today does not guarantee safety tomorrow. While every radiological index indicated safe levels, localized variations in the data warrant continued environmental monitoring, particularly as coastal development, dredging and tourism intensify along the Red Sea shores. Sediment is a dynamic reservoir: storms redistribute sand, wadis deliver fresh mineral load after rare desert floods, and human activities can mobilize metals that were previously locked in stable mineral phases. A baseline like this one, established with rigorous instrumentation and cross-validated by independent methods, is precisely what allows future surveys to detect meaningful change against a well-characterized natural background rather than chasing statistical noise.

The broader significance of the work lies in its methodology. By fusing gamma spectrometry, ICP-MS geochemistry, multivariate statistics and potential-field geophysics, the team has demonstrated a template for environmental assessment that could be applied to any coastline where the geologic setting is complex and the monitoring budget is finite. Gravity data are comparatively cheap to obtain and interpret, and they provide the structural context that pure chemistry cannot. For the millions of people who live along the Red Sea, and the millions more who visit its reefs and beaches each year, the message of this study is simple and welcome: the sand beneath their towels is radiologically benign, its metal content is governed chiefly by ancient mountains rather than modern industry, and the scientific community now has the tools to keep watch as the coastline changes.

Subject of Research: Radiological hazard and heavy metal assessment of Red Sea coastal sediments using geochemical, radiometric and gravity geophysical methods

Article Title: Radiological assessment and heavy metal variability in Red Sea coastal sediments using integrated geochemical and geophysical techniques

Article References: Faraj, T. K., Seif, R. A., Mohamed, W. H., Taalab, S. A., Madkour, H. A., Khandaker, M. U., El-Taher, A., & Hanfi, M. Y. (2026). Radiological assessment and heavy metal variability in Red Sea coastal sediments using integrated geochemical and geophysical techniques. Environmental Geochemistry and Health, 48(16), Article 630. https://doi.org/10.1007/s10653-026-03480-6

Image Credits: AI Generated

DOI: 10.1007/s10653-026-03480-6

Keywords: Red Sea, coastal sediments, natural radioactivity, gamma-ray spectrometry, ICP-MS, heavy metals, radiological hazard indices, Bouguer gravity, principal component analysis, uranium-238, thorium-232, environmental monitoring

The Okpara mine, also known as the Iva Valley mine, has stood unmanaged since its closure, with no post-closure environmental monitoring or containment strategy. That neglect matters because the geology of the Anambra Basin is unforgiving. The Enugu Shale that hosts the coal seams is naturally enriched in uranium and thorium decay chains, meaning the spoil heaps left behind are essentially uncontrolled deposits of naturally occurring radioactive material. When rainwater percolates through these dumps, it generates acid mine drainage, an acidic leachate that mobilizes radium, thorium and other radionuclides and carries them downslope into farmland and waterways. Wind adds a second dispersal pathway, lifting contaminated dust from the spoil piles and scattering it across the surrounding agricultural landscape.

To quantify the hazard, the team collected 24 environmental samples from across the affected area and analyzed them using certified gamma spectrometry, with measurements performed at Activation Analysis Laboratories in Ancaster, Canada, and at the Centre for Energy Research and Training at Ahmadu Bello University in Zaria, Nigeria. The technique identifies and quantifies gamma-emitting isotopes, allowing the researchers to determine activity concentrations of potassium-40, radium-226 and thorium-232 in each sample. From these measurements they derived eight separate hazard indices, all compliant with the assessment frameworks of the United Nations Scientific Committee on the Effects of Atomic Radiation and the International Commission on Radiological Protection, and they estimated dietary ingestion doses based on local cassava consumption, a staple crop grown throughout the valley.

The numbers are striking. Mean activity concentrations of radium-226 reached 51.23 plus or minus 11.79 becquerels per kilogram, exceeding the global average by a factor of 1.46, while thorium-232 averaged 68.86 plus or minus 16.45 becquerels per kilogram, a factor of 2.30 above the worldwide benchmark. The mean outdoor gamma dose rate of 75.64 nanograys per hour surpassed the world average in 87.5 percent of the samples collected. In practical terms, people living and farming in the valley are receiving measurably higher external gamma exposure than the global baseline, simply from the ground beneath their feet.

But the most alarming finding concerns what residents eat. The mean annual dietary ingestion dose was calculated at 2.43 millisieverts per year, exceeding the ICRP public exposure limit of 1 millisievert per year in every single sample, and radium-226 accounted for 68.8 percent of that total dose. Radium’s dominance on the ingestion pathway stems from its relatively high ingestion dose conversion factor, meaning each becquerel consumed delivers a larger effective dose than the same activity of thorium or potassium-40. Because cassava efficiently transfers radium from contaminated soil into its edible tubers, and because cassava forms such a large share of the local diet, the food chain acts as a powerful concentrating mechanism, funneling subsurface radioactivity directly into the bodies of the community.

The statistical structure of the hazard is also revealing. Thorium-232 emerged as the dominant contributor to the calculated outdoor gamma dose, accounting for roughly 55 percent of the outdoor dose rate with a strong correlation coefficient of R-squared equal to 0.804 and a p-value below 0.0001, while radium-226 dominates the ingestion pathway. This split reflects the different physics of the two exposure routes: thorium’s decay chain emits abundant gamma radiation that irradiates the body externally, whereas radium, chemically analogous to calcium, is readily absorbed through the gut and deposited in bone tissue, where its alpha emissions do the most biological damage. The excess lifetime cancer risk, calculated at a mean of 3.25 times ten to the minus four, exceeded global benchmarks in 66.7 percent of cases, translating into a measurable elevation of lifetime cancer probability for people who live and farm in the most contaminated zones.

Spatial analysis added a crucial layer of precision. Using cubic interpolation of the sample data, the researchers mapped contamination gradients across the valley and found that peak concentrations track the acid mine drainage axis in the central-eastern sector of the site. This pattern confirms the mechanistic picture: the acidic drainage channels act as radioactive highways, carrying radium and thorium from the spoil heaps outward into the fields where food is grown. The mapping also carries practical value for remediation, because it identifies exactly where containment and treatment efforts would deliver the greatest reduction in community dose.

The study also uncovered a regulatory blind spot with immediate construction implications. The representative level index, a screening tool used to judge whether earth materials are safe for building, exceeded the threshold value of 1.0 in 75 percent of samples, classifying those materials as unsuitable for unrestricted construction use. Yet in many Nigerian communities, mine spoil and local soil are routinely used for bricks, road fill and foundations, often without any radiological screening. The finding suggests that the hazard extends beyond farming into the built environment, and that material sourcing decisions in the valley may be compounding exposure without anyone realizing it.

What makes the Iva Valley case particularly significant is its comparative severity. According to the comparative data available at the time of writing, the authors identify the site as the most severe documented case of dietary radionuclide burden at a West African coal mine legacy site. It is also a warning about a broader, largely invisible class of risk. Coal mining worldwide disturbs formations that naturally contain uranium and thorium, and abandoned mines across Africa, Asia and Latin America sit unmonitored beside growing populations. Nigeria alone hosts numerous legacy extraction sites where naturally occurring radioactive materials have never been systematically surveyed, and previous studies have flagged elevated radioactivity around gold, tin and coal operations across the country.

The researchers call for immediate interventions, including treatment of the acid mine drainage, physical containment of the spoil heaps, agricultural restrictions in the most contaminated zones, and systematic monitoring of naturally occurring radioactive materials aligned with international safety standards. None of these measures currently exists at the site. The study’s message is ultimately about time: every year of inaction extends the exposure of 50,000 people through the food they eat, the dust they breathe and the ground they walk on. A mine that closed decades ago is still, in a very literal sense, radiating consequences into the present, and the Iva Valley results make a compelling case that legacy mining sites across the region deserve urgent radiological assessment before the hidden burden grows heavier still.

Subject of Research: Radiological hazard assessment of natural radionuclide contamination from a legacy coal mine in Enugu Iva Valley, Nigeria

Article Title: Elevated radiological hazards in a legacy coal mining area: unveiling hidden cancer risks from natural radionuclides in Enugu Iva Valley, Southeast Nigeria

Article References: Omeje, M., Sabri, S., Owusu-Appiah, J., Gyaase, D., & Orosun, M. M. (2026). Elevated radiological hazards in a legacy coal mining area: unveiling hidden cancer risks from natural radionuclides in Enugu Iva Valley, Southeast Nigeria. Environmental Geochemistry and Health, 48(15), Article 624. https://doi.org/10.1007/s10653-026-03502-3

Image Credits: AI Generated

DOI: 10.1007/s10653-026-03502-3

Keywords: natural radioactivity, radium-226, thorium-232, coal mining legacy, acid mine drainage, cancer risk, Enugu Shale, cassava, gamma spectrometry, Nigeria, ICRP, radiological hazard

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

Every beach on Earth carries a faint trace of the planet’s geological origins. Primordial radionuclides, including uranium-238, radium-226, thorium-232 and potassium-40, have existed since the formation of the Earth and are incorporated into the minerals that make up sand, rock and soil. In most coastal environments, these isotopes occur at modest concentrations that pose little concern. But where heavy minerals accumulate, sands can become strikingly radioactive. The Visakhapatnam coast, with its complex geology and active sediment transport, proved to be exactly such a place, and measuring it required laboratory instrumentation of the highest sensitivity.

The research team collected beach sand samples from locations along the coastline and analysed them using a high-purity germanium gamma spectrometry system, a technique prized for its ability to resolve the characteristic gamma-ray signatures emitted by individual radionuclides. High-purity germanium detectors, cooled to reduce thermal noise, can distinguish the faint energy lines of uranium, radium, thorium and potassium decay chains from the background of ambient radiation, allowing precise quantification of each isotope’s activity concentration in units of becquerels per kilogram. The researchers also measured ambient radiation levels directly on the beaches to connect their laboratory findings to real-world exposure conditions.

The results were remarkable. Activity concentrations of uranium-238 ranged from 8.9 to 868 becquerels per kilogram, with a mean of 167. Radium-226 spanned from 2.8 to 1,282.8, averaging 292. The most dramatic findings concerned thorium-232, which ranged from 6.9 to a staggering 13,691.7 becquerels per kilogram, with a mean of 2,614, while potassium-40 ranged from 77.2 to 1,191.1 with a mean of 449. Each of these mean values exceeds the global averages reported for ordinary soils and sediments, and the thorium figures in particular place the most enriched samples firmly in the territory of monazite-bearing sands, the mineral that has made parts of the Indian coastline famous among radiation scientists for decades.

Thorium’s dominance in these sands is no accident. Monazite, a phosphate mineral rich in thorium and rare earth elements, is a hallmark of India’s eastern and southwestern coastal placer deposits. When waves and longshore currents sort sediments by density and grain size, heavy resistant minerals such as monazite, zircon and ilmenite become concentrated into placer deposits, while lighter quartz is winnowed away. Because thorium and its decay products are locked into monazite’s crystal lattice, these deposits act as natural concentrators of radioactivity. The measured absorbed gamma dose rates on the Visakhapatnam beaches, the study found, are comparable to those in monazite-rich high background radiation areas in India and worldwide, confirming that the same mineralogical processes are at work here.

One of the study’s most valuable contributions is its mapping of spatial variability. Rather than presenting a single average figure, the researchers generated spatial distribution maps that visualize the heterogeneity of radionuclide concentrations along the entire study area. These maps revealed a clear pattern: radioactivity levels rise consistently toward the northern sector of the coastline. This gradient likely reflects the interplay of sediment sources, wave-driven transport directions and the geomorphology of the coast, which ranges from sandy beaches to rocky headlands between Visakhapatnam and Bhimunipatnam. The authors also observed that radioactivity varied across the width of individual beaches, meaning that a visitor standing at the waterline may be on sand with a different radiological character than sand collected near the dunes or backshore.

To translate raw activity concentrations into statements about human risk, the team computed a battery of internationally recognized radiological hazard indices. These included radium equivalent activity, which combines the contributions of the uranium and thorium series and potassium into a single comparable quantity; the absorbed gamma dose rate, which estimates the energy deposited in air per unit time; the annual effective dose equivalent, which converts that dose into a projection of yearly health-relevant exposure; the gamma level index; and the external and internal hazard indices used in building-material and land-use assessments. Together, these indices allow the Visakhapatnam data to be compared directly with safety benchmarks established by bodies such as the United Nations Scientific Committee on the Effects of Atomic Radiation and the International Commission on Radiological Protection.

The researchers went beyond measurement and mapping by applying statistical analyses to the relationships among the radionuclides themselves. Correlation analysis indicated a strong relationship between the radium series and the thorium series, a signature that the authors interpret as evidence of a common geological origin for the two decay chains. This makes geochemical sense: both uranium and thorium series isotopes tend to reside in the same heavy mineral phases, so their concentrations rise and fall together as those minerals are concentrated or diluted in the sand. Such correlations transform a set of isolated numbers into a coherent narrative about where the sand comes from and how the coast has sorted it over time.

It is important to keep the findings in perspective. Natural radioactivity in beach sand is not the same as contamination from human activity; these radionuclides are part of the Earth’s crust and have always been present. Millions of people worldwide live safely in high background radiation areas, including the well-studied monazite sands of Chhatrapur in Odisha and regions of Brazil, China and Kerala. What the Visakhapatnam study provides is a rigorous, spatially resolved baseline against which any future changes, whether from coastal engineering, sediment redistribution, or industrial development, can be judged. Baseline data of this quality are the foundation of long-term environmental monitoring and credible radiological risk assessment in coastal ecosystems.

The study also carries a broader message about how science sees ordinary landscapes. A beach that appears uniform to the eye is, to a gamma spectrometer, a patchwork of geological history written in decaying atoms. By combining sensitive nuclear instrumentation, spatial mapping and statistical interpretation, the researchers have shown that radioactivity along a single coastline can vary by three orders of magnitude within short distances. For coastal managers, public health authorities and the millions who visit these shores, the work of Ramesh and his colleagues offers both a caution about localized hotspots and a model of how careful, transparent measurement can turn invisible hazards into mapped, understood and monitorable features of the environment.

Subject of Research: Natural radionuclide distribution and radiological hazard assessment in beach sands of the Visakhapatnam coast, India

Article Title: Spatial distribution of natural radionuclides and radiological hazard assessment in beach sands of the Visakhapatnam coast, Eastern India

Article References: Ramesh, B., Savitri, P. P., Sudhakar, J., Kumar, R. B., Sahoo, S. K., Saradhi, I. V., & Pulhani, V. (2026). Spatial distribution of natural radionuclides and radiological hazard assessment in beach sands of the Visakhapatnam coast, Eastern India. Environmental Monitoring and Assessment, 198(10), Article 1113. https://doi.org/10.1007/s10661-026-15926-6

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15926-6

Keywords: natural radioactivity, gamma spectrometry, beach sand, thorium-232, radium-226, monazite, Visakhapatnam, radiological hazard, spatial distribution, coastal environment, high background radiation, Environmental Monitoring and Assessment

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 research team, led by Aloyce Isaya Amasi of the Nelson Mandela African Institution of Science and Technology together with George Herbert Zinga and Shovi Furaeli Sawe of the Tanzania Atomic Energy Commission, sampled five widely used hot springs distributed across five administrative regions: Chemka/Kikuletwa in Kilimanjaro, Lake Manyara in Manyara, Misughaa in Singida, Songwe in Songwe, and Kilambo in Mbeya. These sites span a remarkable geological range, from the volcanically active Eastern Rift to the central cratonic regions of the country, and each spring serves a different mix of bathers, recreational swimmers, and tourists. Water samples were collected directly at the emergence points and analyzed using an AlphaGUARD professional radon monitor equipped with an AquaKIT arrangement, a reference-grade instrument that measures radon activity concentrations in water through a closed-loop degassing and detection cycle. The choice of instrumentation matters: AlphaGUARD systems have been validated against international reference standards, giving the Tanzanian measurements a level of technical credibility that allows direct comparison with datasets from Europe, Asia, and elsewhere in Africa.

The results revealed striking spatial variability that surprised even the researchers. Radon activity concentrations ranged from a low of 0.56 plus or minus 0.39 becquerels per liter at Songwe to a high of 103.34 plus or minus 44.91 becquerels per liter at Misughaa, a difference of nearly two orders of magnitude across the country. Intermediate values were recorded at Chemka, which averaged 4.96 plus or minus 0.76 becquerels per liter, Kilambo at 9.82 plus or minus 7.58 becquerels per liter, and Lake Manyara at 13.84 plus or minus 2.34 becquerels per liter. Statistical analysis confirmed that the differences among sites were highly significant, with a probability value below 0.001, meaning the variation is almost certainly geological in origin rather than a product of measurement noise or sampling chance. Within individual spring systems, particularly Misughaa and Kilambo, concentrations also fluctuated considerably from one sub-location to another, hinting at complex subsurface plumbing beneath each emergence point.

That internal variability is where the study becomes scientifically rich. The authors attribute the heterogeneity to localized hydrogeological controls, including fracture-mediated groundwater flow, groundwater-rock interaction, and radon degassing that occurs before the water reaches the surface. Radon-222 has a half-life of only 3.8 days, so its concentration in any given water sample is a snapshot of recent contact with radium-bearing rock. Water that travels quickly through fractured crystalline basement picks up radon efficiently, because fractures expose fresh rock surfaces and shorten the transit time during which the gas can decay or escape. Conversely, water that lingers in open pools or shallow reservoirs loses radon to the atmosphere through partitioning at the air-water interface, a process whose efficiency depends strongly on temperature and salinity. The exceptionally high values at Misughaa, where individual samples reached up to 179 becquerels per liter, suggest that this spring taps a radium-rich source zone with rapid fracture-dominated ascent, while the low Songwe values indicate either depleted source rock or extensive pre-emergence degassing.

Against international safety benchmarks, the picture is largely reassuring but not uniformly so. The parametric value of 100 becquerels per liter established by Council Directive 2013/51/Euratom applies to water intended for human consumption, and every site mean fell below that threshold except Misughaa, whose site mean marginally exceeded the guideline and whose individual samples climbed well past it. It is important to note that thermal spring water is not typically consumed as drinking water in the way municipal supplies are; the relevant exposure scenario involves incidental ingestion during bathing and, more significantly, inhalation of radon released from warm water into the often-enclosed spaces of bathhouses and spa facilities. Nevertheless, the Misughaa exceedance matters because it identifies a specific location where sustained human contact with elevated radon levels is a realistic and recurring condition, and where targeted monitoring rather than blanket national regulation would be the proportionate response.

To translate concentrations into health consequences, the team calculated annual effective doses using accepted radiological protection models grounded in the recommendations of the International Commission on Radiological Protection and the exposure factor frameworks of the United States Environmental Protection Agency and the United Nations Scientific Committee on the Effects of Atomic Radiation. Effective dose combines the amount of radiation absorbed with sensitivity weightings for different organs and tissues, yielding a single figure in millisieverts that can be compared against international public exposure limits. The calculations showed that estimated annual effective doses from incidental ingestion remained below internationally recommended public exposure limits at all sites, although the higher end of the dose distribution occurred at Misughaa under frequent exposure scenarios, meaning that people who bathe regularly at that spring accumulate doses meaningfully larger than occasional visitors. The dose estimates also depend on assumptions about ingestion volume, exposure frequency, and the fraction of radon that transfers from water to air, and the authors were careful to frame their results as scenario-based estimates rather than individualized dosimetry.

The Tanzanian findings slot into a growing global literature on radon in thermal waters, and the comparisons are instructive. Studies in western Turkey, northern Pakistan, southern Poland, Slovenia, Hungary, South Africa, and India have documented thermal spring radon concentrations spanning similar ranges, with fracture-controlled geology repeatedly emerging as the dominant predictor of elevated values. The South African study of the Montagu thermal spa resort, for instance, measured radon levels and associated effective doses at a tourist destination structurally analogous to Tanzania’s most visited springs, while work in Slovenia and Hungary emphasized that inhalation in enclosed bathing halls can rival or exceed ingestion as a dose pathway. What distinguishes the new study is not the magnitude of its measurements but the fact that, until now, Tanzania’s substantial geothermal resource base had generated no published radon data whatsoever, leaving regulators at the Tanzania Atomic Energy Commission without an empirical foundation for environmental radiation protection decisions in this sector.

The practical implications extend beyond radiation safety into the economics of geothermal tourism. Tanzania has been actively developing its geothermal resources for both energy production and wellness tourism, and hot springs such as Chemka/Kikuletwa have become destinations for international travelers seeking natural bathing experiences. The new baseline dataset allows the country to integrate radiological monitoring into its emerging geothermal regulatory framework from the outset, rather than retrofitting safeguards after problems arise. The authors argue that their findings support both environmental radiation protection and sustainable geothermal resource management, and the data availability statement indicates that the essential measurements are published within the article while raw datasets can be requested from the corresponding author for academic and non-commercial validation purposes. For a country whose radiation protection infrastructure is still maturing, having defensible, instrument-verified numbers is the prerequisite for every subsequent policy step.

What comes next is likely to be a broader national survey. The five springs sampled here represent a first tranche, and Tanzania hosts dozens of additional thermal manifestations along the Western and Eastern Rift branches whose radon signatures remain unmeasured. The strong link between fracture density and radon concentration observed at Misughaa suggests that future work could combine radon mapping with structural geology and hydrogeological modeling to predict which springs warrant priority monitoring. Repeated seasonal sampling would also clarify whether radon levels fluctuate with recharge patterns, water table position, or seismic activity, a relationship documented in earlier studies of thermal springs in seismically active regions. For now, the message for bathers is measured rather than alarming: the overwhelming majority of Tanzanian thermal waters deliver radon doses well within internationally accepted limits, but the Misughaa spring demonstrates that local geology can push specific sites past guideline values, and that the only way to know which waters are safe for frequent use is to keep measuring them. In the quiet chemistry of hot spring water, Tanzania has found both a public health signal and a new window into the fractured plumbing of the East African Rift.

Subject of Research: Radon-222 concentrations in Tanzanian thermal spring waters and the associated radiological doses to users

Article Title: Assessment of radon concentrations in selected Tanzanian thermal waters and associated radiological risks to users: implications for environmental radiation protection

Article References: Amasi, A. I., Zinga, G. H., & Sawe, S. F. (2026). Assessment of radon concentrations in selected Tanzanian thermal waters and associated radiological risks to users: implications for environmental radiation protection. Environmental Geochemistry and Health, 48(14), Article 584. https://doi.org/10.1007/s10653-026-03468-2

Image Credits: AI Generated

DOI: 10.1007/s10653-026-03468-2

Keywords: radon-222, thermal springs, Tanzania, geothermal water, natural radioactivity, annual effective dose, radiation protection, hydrogeology, groundwater, hot springs, radon monitoring, East African Rift