Drinking water as a substantial source of toxic alkali, alkaline and heavy metals: Toxicity and their implications on human health

Objectives: The objective of the current study was to optimize a highly sensitive method utilizing microwave digestion and iCAP quadrupole inductively coupled plasma mass spectrometry (Q ICP-MS) for the determination of toxic alkali, alkaline and heavy metals in drinking water, and their implications on human health. Methods: A highly sensitive method based on microwave digestion and iCAP Q ICP-MS have been applied for the determination of potential metals alkali (23Na), alkaline (24 Mg) and heavy metals (75As, 208Pb, 111Cd, 59Co, 66Zn and 63Cu) in drinking water of diverse brand and origin. Results: The system has provided excellent quality conditions, such as detection limit (DL, 0.007–0.296 µg/L), quantification limit (QL, 0.023–0.893 µg/L) and coefficient of determination (R², 0.976–0.998) with recovery >99.95%. Amounts of metals in bottled drinking water (BDW) were ranged from not detected to 74847.15 µg/L, whereas, tap water (TW) constitutes 1.12 to 42776.89 µg/L. Average daily dose (ADD, 0.03–516.715 μg/kg/day), hazard quotient (HQ, 0.001–0.08 μg/kg/day) based on heavy metals oral reference dose, and cancer risk (CR, 0.45–244.67 μg/kg/day) based on heavy metals cancer slope factor were achieved for BDW. Nevertheless, ADD (0.03–1028.19 μg/kg/day), HQ (0.01–0.12 μg/kg/day) and CR (0.42–292.80 μg/kg/day) were obtained for TW. As a result, BDW produced lower toxicity values than TW (high risk). Additionally, BDW was found to be brand specific, particularly for international brands that contained zero or very low levels of metals. Conclusions: Current investigations have explored the possible impacts of progressively increasing consumption of drinking water, especially in Saudi Arabia. Up to the present time, the levels of potential heavy metal in such water pose predominantly higher toxicity values in TW. Besides, BDW was found to be the brand specific particularly the international brand which contained either zero or low level of metals. As a result, the results highlight the need for strict policies to address the threat of metals in public water.