Radon (222Rn) activity levels in bottled drinking water in South Africa: an assessment of health risk using Monte Carlo simulations

The increasing consumption of bottled drinking water in South Africa has raised concerns regarding its radiological safety, particularly with Radon-222. This baseline study investigated the activity concentration of 222 Rn in selected bottled drinking water brands from South Africa, using an Ionization Chamber type radon monitor AlphaGUARD (PQ 2000). The measured 222 Rn activity concentration ranged from 0.031 ± 0.005 to 0.198 ± 0.042 Bq/L, with an average of 0.099 ± 0.040 Bq/L. The mean annual effective ingestion dose are 0.344 ± 0.138 μSv/y for infants, 0.206 ± 0.083 μSv/y for children, and 0.175 ± 0.070 μSv/y for adults, all within the recommended international safety limits by WHO and UNSCEAR and are comparable to other published studies. Monte Carlo simulations estimated over a lifetime of exposure, the probabilistic distribution of cancer risk and was within recommended limit. Although the overall risk is low, the presence of 222 Rn in the samples highlights the importance of routine monitoring and quality control in the bottled drinking water industry. It is therefore recommended that regulatory frameworks be strengthened to include radionuclide assessment in bottled drinking water, alongside conventional Physico-chemical and microbiological parameters, to ensure sustained consumer safety.