Water is the single largest input your body takes in every day. Whatever is in your water is in you. That observation is enough to make water filtration one of the higher-leverage exposomic interventions available, and it is one of the cheapest.
Municipal water in the US is generally safe in the sense that it does not make people acutely sick. It is also not optimized for chronic, low-level exposure reduction. Most municipal supplies contain measurable amounts of chlorine, fluoride, disinfection byproducts, trace pharmaceuticals, microplastics, and depending on the source, heavy metals from aging infrastructure.
The cost of removing most of that is a few hundred dollars and a recurring filter replacement.
What is in typical municipal water
A few contaminant categories matter most.
Disinfection byproducts. Chlorine and chloramine are added to kill pathogens. They do their job. They also react with organic matter to produce trihalomethanes and haloacetic acids, both classified as probable human carcinogens at chronic exposure levels.
Heavy metals. Lead from old plumbing remains the largest single concern, particularly in homes built before 1986. Copper, arsenic (in some regional water supplies), and cadmium can also be present.
Pharmaceuticals. Trace levels of medications excreted by populations and not removed by standard treatment. The clinical significance at typical levels is debated. The principle of reducing avoidable exposure stands.
Microplastics. Now detected in most municipal water supplies. The clinical implications are still being researched. Reducing exposure is a reasonable principle.
PFAS (forever chemicals). A growing concern in many regional water supplies. Linked to immune dysfunction, hormone disruption, and certain cancers. Specifically requires filtration designed to remove them.
Fluoride. Added intentionally for dental benefit. The dose-response curve and the balance of benefits and risks is genuinely contested. Reasonable people disagree.
What filtration actually does
Different filter types remove different things.
Activated carbon (countertop pitchers, faucet filters). Removes chlorine, some disinfection byproducts, some pharmaceuticals, some VOCs. Does not effectively remove heavy metals, microplastics, PFAS, or fluoride. The cheapest option and a meaningful upgrade over tap water.
Reverse osmosis (under-sink systems). Removes nearly everything: heavy metals, microplastics, most pharmaceuticals, fluoride, most PFAS. The most thorough common option. Wastes some water in the filtration process.
Distillation. Similar removal profile to reverse osmosis. Slower, more energy-intensive, less convenient.
Whole-house systems. Filter at the point of entry rather than the tap. Useful when water concerns extend to showering, where chlorine and disinfection byproducts can be absorbed through skin and inhaled in steam.
What I recommend clinically
For most patients I prescribe:
Reverse osmosis at the kitchen sink. The high-leverage purchase. Filters the water you drink and cook with, which is most of the daily exposure. Several brands work; the specifics matter less than having one installed and maintained.
A carbon shower filter. Reduces chlorine and chloramine exposure during showers, which represents a meaningful share of total exposure for many adults.
A water test if the case calls for it. Most municipal supplies publish annual water quality reports. Read yours. If you have well water or live in an area with known issues, test directly.
Glass or stainless steel for storage. A clean water source defeated by drinking from a plastic bottle that has been sitting in a hot car is not a win.
What does not need to be done
A few patterns that come up in patient questions but are not necessary for most people.
Alkaline or structured water. No clinical evidence for benefit beyond clean water itself. The marketing exceeds the science.
Hydrogen water. Some research exists. The clinical evidence in humans is not yet strong enough to recommend the cost.
Mineral supplementation after reverse osmosis. Most adults eating a reasonable diet get sufficient minerals from food. The amount you would get from unfiltered water is minor compared to dietary sources.
If you want a physician to read whether your water exposure is showing up in your biology, the path in is the Precision Call.
