Characterization of Metallic Flavor in Drinking Water: An Interdisciplinary Exploration through Sensory Science, Medicine, Health, and the Environment

Scientific explorations can lead to life changing discoveries or light the path for new discoveries as scientists continue to carry or pass on the torch of knowledge to current and future generations. This torch of knowledge radiates in many directions, as the path of discovery often demands a multidimensional perspective. This research explored the many aspects of metallic flavor in drinking water through applications of sensory science, medicine, health, and the environment.

Humans interact with their environment through the five senses and are often exposed to contaminants through multiple routes; oral intake of trace metal contaminants through drinking water is a likely source. The biochemical mechanism by which humans are able to detect the flavor of strongly metallic agents such as iron has been previously elucidated, but little is known about population variability in the ability to sense metallic flavors. This research evaluated sensory thresholds and biochemical indicators of metallic flavor perception in healthy adults for ferrous iron in drinking water; 61 subjects aged 19 – 84 years, participated. The findings demonstrated an age-dependent sensitivity to iron indicating as people age they are less sensitive to metallic perception; impairment of olfactory functions is a contributing factor.

Unlike in healthy adults, where human senses are often protective of overexposure to contaminants, and supportive of sensations of everyday life's pleasures, cancer patients often suffer from chemosensory dysfunctions. Metallic phantom taste is a commonly experienced sensation, yet very little studied aspect of this debilitating disorder. Impact of cancer therapy on chemosensory functions of patients with malignant brain tumors undergoing combined modality treatment (CMT) was explored. The results indicated that chemosensory dysfunctions of the patients can range from minimal to moderate impairment with maximum impairment developing during the 6-week CMT. Study of salivary constituents may provide clues on to the causes of chemosensory dysfunctions.

On health aspects, implication of individual sensitivity to metallic flavor on beverage choices and overall water consumption was assessed in 33 healthy adults through self-reported beverage questionnaire. The results indicated that among the elderly reduced intake of drinking water coincided with reduced sensitivity to metallic flavor. The findings have important health implications in terms of hydration status and beverage choices.

Finally, with environmental exposure relevance, preliminary findings on sensory properties of zerovalent iron nanoparticles (nZVI) indicated that oral exposure to nZVI may induce sensory properties different from that of ferrous iron, likely predictive of a diminished detection of metallic flavor by humans. Further research is warranted in this area.