Water filters: what actually removes carcinogens

The bottom line

Not all water filters are created equal, and most of the popular ones don’t remove the contaminants that matter most for cancer risk. If you’re filtering water for taste, a basic pitcher is fine. If you’re filtering to reduce exposure to carcinogens like arsenic, certain "forever chemicals" (PFAS), and disinfection byproducts, you need to match the filter to the contaminant.

Know what’s in YOUR water first

Before buying anything, find out what you’re actually dealing with. Look up your local water utility’s annual Consumer Confidence Report (they’re required to publish one). Or check the EWG Tap Water Database (ewg.org/tapwater) by zip code. If you’re on a well, get it tested independently — wells aren’t regulated, and arsenic and nitrates are common.

What removes what

• Activated carbon (most pitcher and faucet filters): good for chlorine, some disinfection byproducts, taste and odor. Limited for arsenic, PFAS, or nitrates. Look for filters certified to NSF/ANSI Standard 53 for specific contaminant claims.
• Reverse osmosis (under-sink systems): removes the widest range — arsenic, nitrates, PFAS, many heavy metals, disinfection byproducts. The most thorough option for carcinogen reduction. Wastes some water and removes minerals (a non-issue health-wise).
• Certified PFAS filters: if PFAS ("forever chemicals," linked to kidney and testicular cancer) are in your water, look specifically for filters certified to reduce PFOA/PFOS — reverse osmosis or specific activated carbon blocks tested for it.
• Ion exchange / specialty media: for specific problems like nitrates or arsenic when RO isn’t practical.

The certification that actually matters

Ignore marketing claims. Look for NSF/ANSI certification for the SPECIFIC contaminant you care about. A filter "certified" for chlorine tells you nothing about its arsenic removal. NSF Standard 53 covers health-related contaminants; Standard 58 covers reverse osmosis; Standard 401 covers emerging contaminants. Check the certification for your target, not just that a certification exists.

Practical guidance

For most municipal water: a carbon filter certified to NSF 53 handles the common concerns and improves taste cheaply. If your water report or the EWG database flags arsenic, nitrates, or PFAS, step up to a reverse osmosis system (brands like APEC, Aquasana, and others make certified under-sink units in the $200-$400 range). Match the tool to the actual problem — don’t overspend on filtration you don’t need, and don’t underspend if you have a real contaminant.

Resources

• EWG Tap Water Database: ewg.org/tapwater — search your zip code.
• EPA Safe Drinking Water Hotline: 1-800-426-4791.
• NSF certification search: nsf.org — verify a filter’s specific contaminant claims.
• Your utility’s Consumer Confidence Report (mailed annually or online).