Are Showerhead Filters Retailed Online a Scam? Investigating Water Quality Claims Through a Course-Based Research Experience

Showerhead filters are point-of-use devices installed just before showerheads to alter bathing water quality. Such products are gaining popularity but are presently not under any regulatory oversight. Sellers of showerhead filters make wide-ranging claims, including removing harmful substances, modifying pH, and adding elements to the water matrix, and tout health and cosmetic benefits, but without providing substantiating evidence upfront. This study evaluates selected water chemistry parameters, including pH and concentrations of vitamin C, fluoride, and chlorine, of five showerhead filters sold on Amazon.com and finds that most of the sellers' water quality claims are not met. Instead, some filters change a number of water quality parameters opposite to what is marketed, for example, water hardness and dissolved oxygen. We conclude that the sellers of showerhead filters are, at the very least, guilty of promoting misleading advertisements, but more likely culpable of exploiting pseudoscience to profit from consumers' poor literacy in water chemistry. This study is the outcome of a course-based research experience for senior undergraduate and junior graduate students implemented in a technical elective on environmental physicochemical processes. Through sharing the design and execution of this experimental investigation and discussing the wider pedagogical benefits, this study further aims to stimulate others to explore the integration of research and education. On a broader perspective, this study sheds light on the worrying contagion of pseudoscience in water quality engineering and underscores the urgent need to enlighten the public and promote their scientific literacy.