The current work deals with indoor radon (²²²Rn) concentrations and ambient dose-equivalent rate measurements in the bauxite-bearing areas of the Adamawa region in Cameroon before mining from 2022. In total, 90 Electret Ionization Chambers (EIC) (commercially, EPERM) and 175 Radon Track Detectors (commercially, RADTRAK²) were used to measure ²²²Rn concentrations in dwellings of four localities of the above region. A pocket survey meter (RadEye PRD-ER, Thermo Scientific, Waltham, MA, USA) was used for the ambient dose-equivalent rate measurements. These measurements were followed by calculations of annual doses from inhalation and external exposure. ²²²Rn concentrations were found to vary between 36 ± 8–687 ± 35 Bq m⁻³ with a geometric mean (GM) of 175 ± 16 Bq m⁻³ and 43 ± 12–270 ± 40 Bq m⁻³ with a geometric mean of 101 ± 21 Bq m⁻³ by using EPERM and RADTRAK, respectively. According to RADTRAK data, 51% of dwellings have radon concentrations above the reference level of 100 Bq m⁻³ recommended by the World Health Organization (WHO). The ambient dose equivalent rate ranged between 0.04–0.17 µSv h⁻¹ with the average value of 0.08 µSv h⁻¹. The inhalation dose and annual external effective dose to the public were assessed and found to vary between 0.8–5 mSv with an average value of 2 mSv and 0.3–1.8 mSv with an average value of 0.7 mSv, respectively. Most of the average values in terms of concentration and radiation dose were found to be above the corresponding world averages given by the United Nations Scientific Commission on the Effects of Atomic Radiation (UNSCEAR). Even though the current exposure of members of the public to natural radiation is not critical, the situation could change abruptly when mining starts.

A long-term measurement technique of radon exhalation rate was previously developed using a passive type radon and thoron discriminative monitor and a ventilated type accumulation chamber. In the present study, this technique was applied to evaluate the thoron exhalation rate as well, and long-term measurements of radon and thoron exhalation rates were conducted for four years in Gifu Prefecture. The ventilated type accumulation chamber (0.8 × 0.8 × 1.0 m³) with an open bottom was embedded 15 cm into the ground. The vertical distributions of radon and thoron activity concentrations from the ground were obtained using passive type radon-thoron discriminative monitors (RADUETs). The RADUETs were placed at 1, 3, 10, 30, and 80 cm above the ground inside the accumulation chamber. The measurements were conducted from autumn 2014 to autumn 2018. These long-term results were found to be in good agreement with the values obtained by another methodology. The radon exhalation rates from the ground showed a clearly seasonal variation. Similar to findings of previous studies, radon exhalation rates from summer to autumn were relatively higher than those from winter to spring. In contrast, thoron exhalation rates were not found to show seasonal variation.

Nkamouna-Kongo is a cobalt–nickel deposit located in Lomié, Eastern Cameroon. Mining creates radiation exposure pathways that must be considered in risk management scenarios. RESRAD-ONSITE and RESRAD-BIOTA, developed by the US DOE, assess contaminated sites by deriving cleanup criteria and estimating the radiation dose and risk associated with residual radioactive materials using site-specific parameters. This paper evaluated the radiation dose in biota and the health risk from exposure to naturally occurring radionuclides. The activity of 226Ra, 232Th, and 40K was determined by γ-spectrometry. The internal doses were 2.13 × 10−07, 1.42 × 10−06, and 8.38 × 10−05 Gy d−1 for animals and 2.38 × 10−07, 2.04 × 10−06, and 9.07 × 10−05 Gy d−1 for plants. The maximum total dose of 0.7234 mSv yr−1 was obtained at t = 1 year. The external dose contribution obtained at t = 1 year for all nuclides summed and all component pathways was 0.4 mSv yr−1, above the background radiation dose limit of 2.5 × 10−01 mSv yr−1. A maximum cancer risk of 1.36 × 10−03 was observed at t = 1 year. It was also shown in the RESRAD calculations that the total cancer morbidity risks from plant ingestion, radon (independent of water), and external gamma exposure pathways were greater than those from other exposure pathways. The high risk calculated for 226Ra relative to 232Th and 40K makes it the primary human health concern in the study area. The use of a 1 m cover thickness would remediate the contaminated site to a dose on the order of 10−5 mSv yr−1 for a period of 0 to 100 years. The values of these doses are below the US DOE recommended limits.

The world community has long used natural hot springs for tourist and medicinal purposes. In Indonesia, the province of West Java, which is naturally surrounded by volcanoes, is the main destination for hot spring tourism. This paper is the first report on radon measurements in tourism natural hot spring water in Indonesia as part of radiation protection for public health. The purpose of this paper is to study the contribution of radon doses from natural hot spring water and thereby facilitate radiation protection for public health. A total of 18 water samples were measured with an electrostatic collection type radon monitor (RAD7, Durridge Co., USA). The concentration of radon in natural hot spring water samples in the West Java region, Indonesia ranges from 0.26 to 31 Bq L⁻¹. An estimate of the annual effective dose in the natural hot spring water area ranges from 0.51 to 0.71 mSv with a mean of 0.60 mSv for workers. Meanwhile, the annual effective dose for the public ranges from 0.10 to 0.14 mSv with an average of 0.12 mSv. This value is within the range of the average committed effective dose from inhalation and terrestrial radiation for the general public, 1.7 mSv annually.

This study evaluates the concentrations of trace elements (TEs) in soils from the rutile deposit area of Akonolinga, Cameroon, and analyzes the associated health risks. A total of 25 samples were analyzed using flame atomic absorption spectrometry (FAAS). The results show that TE concentrations follow the decreasing order Fe, Ti, Zr, Mn, Cr, V, Ba, Zn, Nb, Ni, Pb, Ga, Cu, Co, Y, Br, and Sn. Pollution indices and the Pearson correlation matrix reveal moderate correlations between Fe and several other TEs, indicating a common origin. Enrichment Factors show significant enrichment in Zr, Nb, and Ti, with notable enrichment in Cr and Co at certain sites. Although the Geo-Accumulation Index indicates no direct contamination and the overall ecological risk is low, the Contamination Factor reveals high levels for Cr, Nb, Ti, and Zr. The carcinogenic risk is moderate, while non-carcinogenic risks are high for children and considerable for adults. These research highlight the potential public health impacts in this mining region and provide essential baseline data for future environmental risk management.

The aim of the current work was to study natural radioactivity in soil and the correlation between ²²²Rn and ²²⁶Ra in the ground and to assess the onsite and indoor long-term excess cancer risk at the bauxite bearing area of Fongo-Tongo in Western Cameroon. ²²²Rn was measured in the ground at a depth of one meter, using Markus 10 detector. ²²⁶Ra, ²³²Th, and ⁴⁰K activity concentrations were measured in soil by two techniques, in situ and laboratory gamma spectrometry. The mean values of ²²²Rn concentrations in the ground were 69 ± 18 kBqm⁻³ for Fongo-Tongo and 82 ± 34 kBq m⁻³ for the locality of Dschang, respectively. The mean values of ²²⁶Ra, ²³²Th, and ⁴⁰K activity concentrations obtained with in situ gamma spectrometry were 129 ± 22, 205 ± 61, and 224 ± 39 Bq kg⁻¹ for ²²⁶Ra, ²³²Th, and ⁴⁰K, respectively, and those obtained by laboratory gamma spectrometry were 129 ± 23, 184 ± 54, and 237 ± 44 Bq kg⁻¹, respectively. A strong correlation between ²²²Rn and ²²⁶Ra activity concentrations determined by in situ and laboratory measurements (R² = 0.86 and 0.88, respectively) was found. In addition, it is shown that the total excess cancer risk has a maximum value of 8.6 × 10⁻³ at T = 0 year and decreases progressively in the long term. It is also shown that ²²⁶Ra makes a major contribution, i.e., above 70%, to the total excess cancer risk.