Carbon dioxide (CO2) is a natural component of tonic water, contributing to its taste and texture through carbonation. While CO2 is a gas we exhale and can be harmful in high concentrations when inhaled, its presence in tonic water is safe because it is consumed rather than breathed in. The carbonation enhances the drinking experience, providing a refreshing effervescence. Concerns about CO2 toxicity are irrelevant in this context, as the method of consumption significantly alters its effects.