Before we dive into why filtered water is good for you, let's explore what might be lurking in your unfiltered tap water. Recent studies have identified several categories of contaminants that could be present in your drinking water, each with its own potential impacts on health and water quality (3).
Physical Contaminants
Physical contaminants are the most visible category of water impurities. These include sediment, organic material, small pieces of degrading pipes, and rust particles. Their presence can affect water's appearance and taste. More importantly, they can indicate underlying infrastructure problems that need attention.
Chemical Contaminants
Chemical contaminants are perhaps the most concerning category. Research has identified several common chemicals in tap water:
Chlorine and Chloramines
Chlorine is a disinfectant used to kill germs/bacteria in water while chloramines are a group of chemical compounds that contain chlorine and ammonia. The type of chloramine used to kill germs/bacteria in drinking water is called monochloramine.
While they're commonly used for municipal water treatment, chlorine and chloramines can (5):
- Create potentially harmful disinfection byproducts
- Cause an unpleasant taste and smell
- Irritate sensitive skin and eyes
- Potentially damage beneficial gut bacteria
They're also responsible for that distinctive "pool water" smell and taste that many people (including myself) find unpleasant.
Native Note: Chloramine in water can contaminate the dialysis fluid and enter the blood of a dialysis patient. Once it enters the bloodstream, chloramines can also alter hemoglobin and cause acute hemolytic anemia and has even led to two epidemics in dialyzed uremic patients (6).
Heavy Metals
Common heavy metals found in tap water include:
- Lead (from old pipes and fixtures)
- Copper (from plumbing)
- Mercury (from industrial pollution)
- Arsenic (naturally occurring in some regions)
A 2023 Environmental Working Group study found that even low levels of these metals, when consumed over time, may contribute to health issues including lung and kidney damage, cognitive impairment, fatigue, and gastrointestinal distress (7).
Pharmaceutical Residues
Modern water treatment plants weren't designed to remove medications that enter the water supply through human excretion. Trace amounts of various drugs have been detected in tap water, including (8):
- Pain relievers
- Antibiotics
- Hormones
- Antidepressants
While the concentrations are low, the long-term effects of chronic exposure to these compounds remain poorly understood.
Biological Contaminants
While municipal water treatment is generally effective at eliminating harmful bacteria, some microorganisms have evolved to resist standard treatment methods. For example, cryptosporidium—a parasite that causes diarrhea—can survive chlorine treatment (9).
Other potential biological contaminants include Giardia cysts, various bacteria strains, and viruses. These organisms pose particular risks for individuals with compromised immune systems.
Emerging Contaminants
Scientists are increasingly concerned about newly identified contaminants in our water supply. Microplastics have become ubiquitous in water sources worldwide, with uncertain health implications.
PFAS, often called "forever chemicals," persist in the environment and are linked to various health concerns (3). Pesticide residues and industrial chemicals continue to enter our water systems through runoff and industrial processes.
