Assessment of soil moisture on radon levels, radon exhalation, natural radioactivity, and radiological risks in offices and laboratories in GAEC

Abstract

This study investigates the influence of moisture on soil radon exhalation, natural radioactivity in soil, and indoor radon concentrations in offices and laboratories at the Ghana Atomic Energy Commission (GAEC) and their associated radiological risks to workers. Radon exhalation rates were determined using the Sealed Can method. CR-39 SSNTD detectors were used to measure indoor radon concentrations. Gamma spectroscopy using HpGe detector was used to determine the activity concentrations of U-238, Ra-226, Th-232, and K-40 in the soil samples. The results showed mean concentrations of 14.3 ± 2.0 Bq/kg (CI 95%: 10.0–18.0) for U-238, 145.0 ± 10.0 Bq/kg (CI 95%:123.0–167.0) for K-40, 31.5 ± 6.0 Bq/kg (CI 95%: 24.0–39.0) for Th-232, and 15.6 ± 2.0 Bq/kg (CI 95%:14.0–29.0) for Ra-226. The results showed mean surface and mass exhalation rates of 6.9 ± 2.3 × 10⁻⁴ Bq/m²/h¹ (CI 95%: 5.7 × 10⁻⁴ –12.6 × 10⁻⁴) and 2.4 ± 0.4 (CI 95%: 1.9–4.2) nBq/kg¹/h¹ respectively. The findings revealed mean indoor radon concentrations of 93.0 ± 10.0 Bq/m³ (CI 95%: 88.0–98.0), 111.0 ± 12.0 Bq/m³ (CI 95%: 102.0–119.0) and 145.0 ± 13.0 Bq/m³ (CI 95%: 135.0–155.0) in the offices, laboratories, and basements respectively, with laboratories and basements exceeding the WHO reference level of 100 Bq/m³. A strong inverse relationship between moisture levels and exhalation rates (r = −0.8) was observed, leading to a negative correlation (r = −0.3). Between the moisture levels and indoor radon levels. The research findings indicated a mean annual effective dose of 0.6 mSv/yr. (CI 95%: 0.5–0.6) to the workers, which is well below occupational and public dose limits. The lung cancer cases of workers were computed which ranged from 0.9 × 10⁻⁸ to 1.2 × 10⁻⁸ cases per million people per year, which is less than the limit range of 170–230 per million people per year recommended by ICRP but remaining with safe radiological limits for workers. This study identified moderate radon exposure risks at the GAEC, exceeding the WHO recommendation. The correlation and trend analysis demonstrate strong relationships between moisture, exhalation rates, radium, and indoor radon.