Deep beneath the farmlands of northwestern Tanzania, radiation has always been there. It comes from uranium, thorium, and potassium locked into the Archean rocks of the Lake Victoria goldfields, the same geological formations that made the region one of Africa’s richest gold provinces. A new study published in Heliyon has now, for the first time, paired high-precision measurements of that natural radioactivity with a large survey of what local residents actually know and believe about it around the Geita Gold Mine, one of Tanzania’s largest gold operations. The result is an unusual and sobering combination: environmental radiation levels that are, for the most part, reassuringly safe, alongside a community largely in the dark about the invisible hazard beneath their feet.
Naturally occurring radioactive material, known in the radiation-protection world as NORM, refers to materials containing uranium-238, thorium-232, and potassium-40, together with their decay products such as radium-226 and radon gas. These radionuclides are everywhere in the Earth’s crust, and in undisturbed settings they pose minimal risk. The concern arises when human activity, particularly mining and mineral processing, concentrates and mobilizes them. Excavation, crushing of ore, and the improper disposal of waste rock and tailings can bring elevated NORM levels into contact with soil, water, and air. Chronic exposure through ingestion, inhalation, or skin contact has been linked to increased risks of lung, bone, and kidney cancers, in part because specific radionuclides accumulate in specific organs: thorium in the lungs and bones, uranium in the lungs and kidneys, and radium in the skeleton, where it chemically mimics calcium.
The Geita district is geologically primed for such enrichment. The mine sits within Archean banded iron formations, felsic volcanic rocks, and intermediate lithologies such as andesite and diorite. Banded iron formations and associated volcanic and intrusive rocks frequently host uraninite and thorite, the primary minerals of uranium and thorium, while amphibole- and biotite-bearing rocks add further natural radioactivity. Earlier studies had already recorded slightly elevated NORM levels in tailings and waste rock at the site, and similar findings have emerged from artisanal mining areas such as Rwamagasa and Buhemba. Yet despite Tanzania’s robust national radiation-safety framework, no sector-specific guidelines exist for managing NORM from gold mining, leaving a regulatory gap that the study’s authors say can produce inconsistent safety practices and uninformed land use.
To close that gap, the research team, led by Jerome M. Mwimanzi of the Nelson Mandela African Institution of Science and Technology and colleagues from institutions in Tanzania, Austria, Croatia, and South Africa, combined two methods rarely deployed together in the region. The first was high-resolution gamma-ray spectrometry of agricultural soils collected from ten farms across six villages surrounding the mine: Machinjioni, Mgusu, and Nyakabale in the Mgusu ward, and Mpomvu, Nyamalembo, and Samina in the Mtakuja ward. Sampling points were chosen using a stratified random design informed by isopleths from an AERMOD atmospheric dispersion model, capturing gradients of exposure tied to the tailings storage facility, waste rock dumps, and modeled ground-level particulate concentrations.
The analytical work was carried out at the Tanzania Atomic Energy Commission laboratory in Arusha. Soil samples were taken from the top 30 centimeters with a stainless-steel auger during the September 2023 dry season, oven-dried at 80 degrees Celsius, ground, and sieved through a 200-micrometer mesh before being sealed in canisters for four weeks. That waiting period is not arbitrary: it allows secular equilibrium to be established between radium-226, radium-224, and the short-lived daughters of radon-222 and radon-220, ensuring that gamma emissions from progeny nuclides faithfully reflect parent activities. Each sample was then counted for 50,000 seconds in a high-purity germanium coaxial detector housed in lead shielding, with radionuclides identified by their characteristic gamma energies: lead-214 and bismuth-214 lines for radium-226, actinium-228 and lead-212 for the thorium series, and the 1,460-keV line of potassium-40. Energy and efficiency calibration were performed with a multi-nuclide standard from the Czech Metrology Institute, and background corrections allowed quantification down to low minimum detectable activities.
The radiometric results were, on the whole, within internationally accepted limits. Average activity concentrations were 53 plus or minus 7 becquerels per kilogram for radium-226, 36 plus or minus 5 for thorium-232, and 205 plus or minus 38 for potassium-40. Radium-226 exceeded the global average of 35 becquerels per kilogram reported by the United Nations Scientific Committee on the Effects of Atomic Radiation, but thorium and potassium sat below their respective global benchmarks of 45 and 420. From these activities the team computed a battery of hazard indices. Radium equivalent activity averaged 121 plus or minus 12 becquerels per kilogram, well below the 370-threshold associated with a one-millisievert annual public dose. External and internal hazard indices averaged 0.30 and 0.5, both far under the limit of 1. The absorbed gamma dose rate averaged 55 nanograys per hour, just under the global population-weighted average of 59, and the outdoor annual effective dose equivalent averaged 67 microsieverts per year, slightly below the global figure of 70. The excess lifetime cancer risk estimates, 0.24 times ten to the minus three outdoors and 0.94 times ten to the minus three indoors, were also below global averages, though indoor risk was notably higher than outdoor, a pattern the authors link to occupancy time and possibly radon accumulation in dwellings.
Two findings stand out from the environmental data. First, the annual gonadal dose equivalent averaged 380 microsieverts per year, above the global threshold of 300 but well under the 1,000-microsievert hazard limit, driven primarily by radium-226 and thorium-232. Second, internal organ doses were roughly five times higher than external ones across all organs, highlighting inhalation and ingestion as the dominant exposure pathways. The village of Machinjioni recorded the highest cancer-risk values, likely a combination of local geology and surrounding artisanal mining, while the highest organ doses clustered in samples from Nyakabale. A correlation analysis showed that radium-226 and thorium-232, not potassium-40, dominate the absorbed dose, with the absorbed dose rate and annual effective dose showing a perfect monotonic relationship, as expected from their linked equations.
The second half of the study turned from gamma spectra to human voices. Using Yamane’s formula on the 12,856 households of the two wards, the team calculated a required sample of roughly 390 respondents and interviewed exactly that number, 65 from each village, through structured questionnaires administered by trained assistants with ethical approval from the Tanzania Commission for Science and Technology. The demographics skewed female, 59.7 percent, because sampling occurred during the day when many men were at work, and educational attainment was modest: 62.6 percent had only primary schooling, while 7.4 percent had university education.
The awareness results were striking. Overall, 64.6 percent of respondents had never heard of NORM at all. Gender made no significant difference, but age, education, and occupation did. Younger residents were more aware, plausibly owing to greater access to digital media and environmental education. Education showed the strongest association with awareness, a chi-square of 89.37 with a p-value below 0.01, and occupation was nearly as powerful: awareness ranged from 16.7 percent among peasant farmers to 88.5 percent among government employees, presumably reflecting access to structured information channels. For a community whose livelihoods revolve around farming, livestock, and fishing on mine-adjacent land, the near-blind spot among agricultural workers is the study’s most consequential finding.
Yet among the 138 respondents who did know about NORM, concern ran high. On a five-point scale, residents rated the impact on wildlife highest at a mean of 4.48, followed by water quality at 4.41, air quality at 4.34, and the natural environment at 4.25, with human health at 4.21, yielding an overall “very high” perception score. Correlations among these perceptions showed that residents hold an integrated view of environmental degradation, linking water, air, wildlife, and agriculture, but perceived health impacts correlated with none of the environmental variables, suggesting people sense the ecosystem is damaged without understanding the pathways by which radiation might reach their own bodies. Qualitative accounts sharpened the picture: residents of Nyakabale, Mtakuja, and Mgusu reported rises in miscarriages, neonatal complications, and persistent respiratory symptoms attributed to dust from ore processing, concerns echoed in the Geita Town Master Plan’s documentation of escalating respiratory disease. Declining crop yields at Nyakabale were also attributed to contamination.
The authors are careful about limits. Ten soil samples cannot characterize an entire mining landscape; the survey captures one dry-season moment and self-reported perceptions, not causality; and the dose models rely on standard assumptions rather than personal dosimetry, radon monitoring, or food-chain measurements. But the policy message is clear. The soils around the Geita Gold Mine are, by standard hazard indices, safe under current conditions, yet the combination of localized hot spots, an unregulated NORM sector, and a community that is two-thirds unaware of the hazard leaves little room for complacency. The authors call for combining ongoing radiological surveillance with targeted education campaigns delivered through community meetings, schools, and local radio, aimed especially at older residents, people with limited schooling, and farming households. Radiation, being invisible and silent, only becomes dangerous when its existence is unknown; this study suggests that in Geita, closing the knowledge gap may matter as much as any measurement.
Subject of Research: Assessment of naturally occurring radioactive material (NORM) in agricultural soils and community awareness and perceptions of radiological risks near the Geita Gold Mine, Tanzania.
Subject of Research: Biology
Article Title: Know your NORM: Assessing awareness and perception of naturally occurring radioactive material (NORM) among residents near the Geita gold mine in Tanzania
Article References: Mwimanzi, J. M., Haneklaus, N. H., Amasi, A. I., Bituh, T., Brink, H., Chuma, F. M., Mwalongo, D. A., Lolila, F., Marwa, J. J., Rwiza, M. J., & Mtei, K. M. (2026). Know your NORM: Assessing awareness and perception of naturally occurring radioactive material (NORM) among residents near the Geita gold mine in Tanzania. Heliyon, 12(14), Article e45384. https://doi.org/10.1016/j.heliyon.2026.e45384
Image Credits: AI Generated
DOI: 10.1016/j.heliyon.2026.e45384
Keywords: naturally occurring radioactive material, NORM, Geita Gold Mine, gamma-ray spectrometry, radiological risk, radium-226, thorium-232, potassium-40, community awareness, radiation risk perception, gold mining, Tanzania
Cite Scienmag News
APA MLA Chicago
Drew Townsend. (September 10, 2026). Residents near Tanzanian gold mine show limited awareness of radioactive materials. Scienmag. https://scienmag.com/residents-near-tanzanian-gold-mine-show-limited-awareness-of-radioactive-materials/
Drew Townsend. “Residents near Tanzanian gold mine show limited awareness of radioactive materials.” Scienmag, 10 September 2026, https://scienmag.com/residents-near-tanzanian-gold-mine-show-limited-awareness-of-radioactive-materials/. Accessed 10 September 2026.
Drew Townsend. “Residents near Tanzanian gold mine show limited awareness of radioactive materials.” Scienmag. September 10, 2026. https://scienmag.com/residents-near-tanzanian-gold-mine-show-limited-awareness-of-radioactive-materials/
Copy citation Download RIS
Tags: and potassium in geological formationscommunity awareness of radiation hazardscommunity knowledge of radiation hazardsenvironmental radiation safety in Tanzaniaenvironmental radioactivity levelsgeological sources of natural radioactivityhealth risks of natural radionuclideshealth risks of radioactive materialsimpact of gold mining on radioactivity levelsimpact of mining on radioactivityNatural radioactivity in Tanzania gold mine regionsnatural radioactivity in Tanzanian gold mining regionsNORM (Naturally Occurring Radioactive Materials) in mining areasNORM in mineral extraction processespublic perception of environmental hazardspublic perception of environmental radiation dangersradioactive waste management in Tanzaniaradon gas and decay productsradon gas emissions in mining areasresident awareness of radioactive materialsrisk assessment of radioactive materials in mining communitiessafety of radiation exposure near gold minesthoriumuraniumuranium and thorium in Archean rocks
