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 (R
2 = 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.
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