# Radon Levels of Water Sources in the Southwest Coastal Region of Peninsular Malaysia
## 3 Results and Discussion
The lower radon concentration values in tap water are expected, herein, since the water was mainly comprised of surface water such as in lakes, rivers, and reservoirs with the radon easily released into the air. Additionally, in many situations, water is supplied to residential housing from storage tanks, and the length of pipeline should also be taken into consideration for understanding why the radon in tap water may be low as compared with other sources. The results obtained in this study were compared with those from other locations in Malaysia and other parts of the world, as shown in Table 2. Notably, in this study, the average radon concentrations of all samples did not exceed the WHO guidelines of 100 Bq l\({}^{-1}\) as a safe limit for drinking water [7; 21; 32; 33]. Nevertheless, the radon concentrations in the water samples from the hot spring water and groundwater were above those recommended for drinking water by the United States Environmental Protection Agency (USEPA); however, the other water sources were all below the recommended limit of 11.1 Bq l\({}^{-1}\)[13; 15; 34]. The total annual effective doses due to ingestion and inhalation of radon in drinking water were assessed using the procedures recorded in the UNSCEAR (2000). Table 3 shows the calculated annual effective doses based on the analyzed samples of water taken from each of the sampling sites to the population. The annual effective dose for an adult due to radon in drinking water for ingestion and inhalation varied from practically negligible (below limits of detection) to 39.167 uSv y\({}^{-1}\) and from practically negligible to 0.47 uSv y\({}^{-1}\), respectively. In this study, the average dose calculated from the intakes of radon in drinking water is extremely low at 0.06 uSv y\({}^{-1}\) via inhalation and 4.45 uSv y\({}^{-1}\) from ingestion. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Water Sources**} & \multirow{2}{*}{**State and Country**} & \multicolumn{4}{c}{**Radon Concentration (Bq l\({}^{-1}\))**} & \multirow{2}{*}{**Reference**} \\ \cline{3-4} \cline{6-7}  & & & **Min** & & **Max** & & **Mean** \\ \hline \multirow{4}{*}{1} & \multirow{4}{*}{Groundwater} & Gadau Nigeria & 4.92 & 82.89 & 38.3 & [14] \\  & & Rajasthan, India & 12.5 \(\pm\) 1.5 & 862 \(\pm\) 38 & 113 & [30] \\  & & Yemen & 1.03 \(\pm\) 0.16 & 895.91 \(\pm\) 0.77 & 226.41 \(\pm\) 62.39 & [35] \\  & & Saudi Arabia & 0.01 & 67.4 & 4.62 & [36] \\  & & The Southwest Coastal of & & & & \\  & & Peninsula Malaysia (Negeri & 7.42 & 89.12 & 32.36 \(\pm\) 1.8 & Present study \\  & & Sembilian and Malacca) & & & & \\ \hline \multirow{4}{*}{2} & \multirow{4}{*}{Tap water} & Turkey & 5.31 & 18.46 & 10.82 & [22] \\  & & Sungai Petani, Kedah & - & - & \(5.37\pm 0.58\) & [32] \\  & & The Southwest Coastal of & & & & \\  & & Peninsula Malaysia (Negeri & 0.68 & 3.98 & 1.95 \(\pm\) 0.61 & Present study \\  & & Sembilian and Malacca) & & & & \\ \hline \multirow{4}{*}{3} & \multirow{4}{*}{Hot spring} & Thailand & 95 & 154 & - & [24] \\  & & Northern Venezuela & 1 & 560 & - & [26] \\ \cline{1-1}  & & The Southwest Coastal of & & & & \\ \cline{1-1}  & & Peninsula Malaysia (Negeri & 8.05 & 186.5 & 98.56 \(\pm\) 5.88 & Present study \\ \cline{1-1}  & & Sembilian and Malacca) & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Radon activity concentration in water in other parts of Malaysia and the world. Thus, the total annual effective dose from both inhalation and ingestion ranged from 0.02 to 39.64 eV y\({}^{-1}\), with an average of 4.51 eV y\({}^{-1}\). In Table 4, the annual effective dose for ingestion of radon from drinking water in others states and countries ranged from 0.1 to 65200 eV y\({}^{-1}\) and the recorded average was from 1.76 to 3920 eV y\({}^{-1}\). Elsewhere, the annual effective dose for ingestion of radon ranged from 0.01 to 56,600 eV y\({}^{-1}\), with the recorded average from 0.1 to 570.6 eV y\({}^{-1}\).