Water

The dangers that made water famous, cholera and typhoid, were solved a century ago by disinfection, and that fix still works. Today's concerns are quieter. Lead from old plumbing can affect a child's developing brain, and health agencies have concluded there is no level of it known to be safe.

Forever chemicals (PFAS, long-lasting industrial compounds) build up in the body over years, and nearly every American adult already carries some in their blood. And the chlorine that protects water on its way to you leaves behind byproducts that research links to higher cancer risk over long-term exposure. None of these have a taste or a smell.

They work on the timescale of years of ordinary glasses of water, which is exactly why they are easy to ignore and worth taking seriously.

There are two doors. The first is the water itself. Forever chemicals arrive with the source water, in the rivers, wells, and reservoirs your utility draws from, so your level depends on where your water starts, and you cannot tell by looking.

Disinfection byproducts form along the way, when chlorine reacts with natural organic matter in the water, so if your supply is chlorinated, and almost all municipal water is, some amount reaches every tap. The second door is your own house. Lead is usually a house problem.

It dissolves into water that sits in contact with older plumbing: pipe solder used before 1986, brass fittings made before 2014, and, in some older cities, the service line connecting your house to the main. Your utility's report can be spotless and still say nothing about that last stretch, because its responsibility ends at the curb.

For lead, the age of your home matters more than your zip code.

Start by finding out what is in your water, because the right fix depends on the finding. Your utility publishes a water quality report every year, and it is worth reading, but it describes the system as a whole and stops before your plumbing. A test from your own tap is the only measurement that includes your house.

Once you know what you are dealing with, the fixes are ordinary and within reach.

Different filters do different jobs: a simple carbon filter handles chlorine byproducts and taste, while removing forever chemicals or lead calls for a filter certified for that specific job, often a reverse osmosis system (one that forces water through an extremely fine membrane). No single filter removes everything, and you should not need everything.

Test first, then fix only what the results show.