Environment & Exposure · Updated September 2026
Almost every water filter sold improves taste. Far fewer are certified to remove lead, and fewer still remove PFAS. The certification, not the marketing, is the entire purchase.
This is the step that determines everything else, and it is usually skipped. Buying a filter without knowing your contaminants is buying a solution to an unidentified problem — and different technologies remove entirely different things. Carbon does very little for nitrate. Reverse osmosis removes almost everything including beneficial minerals. Filters certified for taste and chlorine may do nothing measurable for lead.
Your utility's annual water quality report. Public water systems in most countries publish one. It tells you what is in the water leaving the treatment plant — which is not necessarily what arrives at your tap.
A certified laboratory test of your own tap water. The only way to detect lead from your own service line or household plumbing, which is where most lead exposure originates. Utility reports cannot capture this.
Public PFAS mapping. Several countries and NGOs publish maps of detected PFAS contamination by water system. Worth checking before assuming you need PFAS-specific filtration.
The lead point deserves emphasis. Lead in drinking water rarely comes from the source or the treatment plant; it comes from lead service lines, lead solder in older plumbing, and brass fittings. That means your neighbour's water and your water can differ, and only a test of your own tap tells you which situation you are in.
The word “filter” is unregulated. What is regulated is certification against published standards, tested by an accredited body, for specific named contaminants at specific reduction percentages.
| Standard | What it covers |
|---|---|
| NSF/ANSI 42 | Aesthetic — chlorine taste and odour, particulates. Not health contaminants. |
| NSF/ANSI 53 | Health-related — lead, cysts, VOCs, and specified others |
| NSF/ANSI 58 | Reverse osmosis systems, including dissolved solids |
| NSF/ANSI 401 | Emerging contaminants — pharmaceutical residues, some pesticides |
| NSF/ANSI 53 or P473 | PFOA and PFOS reduction specifically |
| NSF/ANSI 244 | Microbiological reduction for supplemental treatment |
A pitcher certified only to Standard 42 makes water taste better and is not a lead filter, regardless of what the packaging implies. Check the certification listing for the specific claim you care about, by model number — certifications are per-product, and a brand certifying one model does not certify its range.
Per- and polyfluoroalkyl substances are a large family of synthetic compounds built around carbon-fluorine bonds, among the strongest in organic chemistry, which is why they neither break down in the environment nor clear quickly from the body. They are associated in the epidemiological literature with effects on cholesterol, immune response, thyroid function, and certain cancers, and the regulatory limits set for them are extraordinarily low — parts per trillion rather than parts per billion.
The practical point for filtration: not all carbon filters remove PFAS meaningfully, contact time matters a great deal, and the technologies with the best evidence are reverse osmosis, high-quality granular activated carbon in sufficient volume, and anion exchange resin. Look for explicit PFOA/PFOS certification rather than assuming a carbon block handles it.
| Technology | Strong on | Weak on | Cost |
|---|---|---|---|
| Carbon pitcher / faucet | Chlorine, taste, some certified for lead | Nitrate, fluoride, dissolved solids; slow | $ |
| Under-sink carbon block | Lead, VOCs, chlorine, cysts if certified | Nitrate, dissolved solids | $$ |
| Reverse osmosis | Almost everything — PFAS, nitrate, lead, dissolved solids | Wastes water; strips minerals; slower | $$$ |
| Whole-house | Sediment, chlorine at every tap | Rarely certified for lead at point of use | $$$$ |
| Distillation | Nearly all dissolved contaminants | Slow, energy-hungry, removes minerals | $$ |
RO is the most comprehensive consumer option and it has three real costs. It produces wastewater — older systems discarded several litres per litre produced, though modern ones are considerably better. It strips beneficial minerals along with contaminants, which is why many systems add a remineralisation stage, and why RO water tastes flat without one. And it is slow, which is why RO systems use a storage tank.
None of these is a reason to avoid RO if you have PFAS, nitrate or high dissolved solids. They are reasons not to install one reflexively if a certified carbon block addresses what is actually in your water at a fraction of the cost and complexity.
A filter past its rated capacity does not stop working visibly. Carbon can release accumulated contaminants back into the water once saturated, and a channelled or clogged filter passes water around the media rather than through it. The certification applies to the rated capacity; beyond it, nothing is certified.
Track litres or set a calendar reminder rather than relying on taste, because taste is governed by chlorine removal, which typically fails last. Water that still tastes fine can be well past the point where the lead or PFAS claim holds.
If your home has lead service lines or old plumbing, water that has sat in the pipes overnight carries far more lead than water that has been running. Running the tap for 30 seconds to two minutes before drinking or cooking meaningfully reduces exposure and costs nothing. Always use cold water for drinking and cooking — hot water dissolves lead from plumbing more readily, and this is one of the most consistently overlooked pieces of advice in the area.
Bottled water is not subject to more rigorous contaminant testing than mains supply in most jurisdictions — in several it is regulated less tightly. Independent testing has found PFAS in a range of bottled brands, and the microplastics literature on bottled water is not reassuring. As a solution to a contaminant problem it is expensive, environmentally poor, and not demonstrably cleaner.
Carbon filters do not remove fluoride; removing it requires reverse osmosis, distillation or activated alumina. Whether you should want to is a separate question, and the mainstream position among dental and public health bodies is that fluoridation at recommended concentrations reduces tooth decay. If you choose to remove it, note that you are removing an intentionally added public health measure rather than a contaminant, and plan dental prevention accordingly.
NSF/ANSI 53 for lead, 53 or P473 for PFOA/PFOS, 58 for RO. Standard 42 alone is taste and odour, not health.
Certifications are per-product. A brand certifying one model does not certify the rest of its range.
Lead usually comes from your service line and plumbing, not the treatment plant. A utility report cannot tell you about your house.
Rated in litres, not months. Beyond the rated capacity, nothing is certified — and saturated carbon can release what it captured.
Ranked by what each is certified to actually remove rather than by convenience. The test kit is first because buying filtration without knowing your contaminants is guesswork.
The only way to know what is in the water at your tap, as opposed to what left the treatment plant. Lead in particular comes from your own service line and plumbing, so a utility report cannot answer the question for your house. Costs less than a year of filter cartridges and determines whether you need a $40 pitcher or a $300 reverse osmosis system.
View on AmazonFor the most common real-world problem — lead from household plumbing plus chlorine taste — a properly certified carbon block under the sink is the right answer. It runs at full tap pressure with no storage tank, wastes no water, keeps beneficial minerals, and costs a fraction of reverse osmosis. Verify the certification by model number for the specific contaminant you care about.
View on AmazonThe right choice when your test comes back with PFAS, nitrate or high dissolved solids — problems carbon cannot address. The honest trade-offs are wastewater, a slower flow through a storage tank, and stripped minerals, which is why a remineralisation stage matters for both taste and sensible mineral intake. Do not install one reflexively if carbon covers your actual contaminants.
View on AmazonMost pitchers are certified only for taste and chlorine. A minority carry genuine NSF 53 or P473 certification for lead and PFOA/PFOS, and those are a real option for renters or anyone who cannot install under-sink plumbing. Check the certification for the exact model — within a single brand's pitcher range, one filter may be certified and another not.
View on AmazonA filter past its rated capacity does not announce itself — taste is governed by chlorine removal, which typically fails last, so water can taste fine long after the lead or PFAS claim has lapsed. Saturated carbon can also release accumulated contaminants back into the water. Buying cartridges ahead and setting a reminder is what keeps a certified system actually certified.
View on AmazonStart with your utility's annual water quality report, which covers what leaves the treatment plant. Then test your own tap through a certified lab, because lead almost always comes from your service line, solder and fittings rather than the source — meaning your water and your neighbour's can genuinely differ. For PFAS, several public mapping projects show detections by water system.
Only the models specifically certified to NSF/ANSI 53 for lead, which is a minority. Most pitcher filters are certified to Standard 42, which covers chlorine taste and odour and makes no health-contaminant claim. Certification is per model number, so check the specific filter you are buying rather than the brand.
Reverse osmosis, high-quality granular activated carbon in sufficient volume with adequate contact time, and anion exchange resin. Not every carbon filter qualifies — contact time and carbon quality matter a great deal — so look for explicit NSF/ANSI 53 or P473 certification for PFOA and PFOS rather than assuming a carbon block handles it.
It does strip calcium and magnesium along with contaminants, and RO water tastes flat as a result. Dietary intake of these minerals from food vastly exceeds what drinking water contributes for most people, so the health concern is generally overstated — but a remineralisation stage is worth having for taste, and it costs little. If your water is your main magnesium source, that is a separate problem worth addressing through diet.
Generally no. Bottled water is not held to more rigorous contaminant standards than mains supply in most jurisdictions and in several is regulated less tightly. Independent testing has found PFAS in a range of bottled brands, and the microplastics findings are not reassuring. A properly certified filter on a tested supply is cheaper, cleaner and better characterised.
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