Which filter fits which contaminant

Short answer

No single filter handles everything. A whole-house filter is best for chlorine, hardness and microbes; a certified tap-level filter or RO unit is the usual answer for lead, nitrate and PFAS.

Always match the claim on the NSF listing to the contaminant. Certification is contaminant-specific.
Test first: a utility's system-wide data cannot tell you what your tap contains.

Contaminant	Technology	Look for	Whole-house?	At the tap?
PFAS (PFOA, PFOS, PFHxS, PFNA, HFPO-DA)	Activated carbon (GAC) - NSF/ANSI 53 PFAS claim; Reverse osmosis - NSF/ANSI 58 PFAS claim; Anion exchange (certified under 53)	NSF/ANSI 53 (carbon, ion exchange) and 58 (RO); the former NSF P473 PFOA/PFOS protocol was folded into 53 and 58	PARTIAL / NOT PROVEN TO MCL. Whole-house (point-of-entry) carbon is used by states for PFAS, usually two vessels in series, but the certification claim is <20 ppt combined PFAS, above the 4 ppt PFOA/PFOS MCL. Softeners and iron filters do not remove PFAS.	RO (NSF/ANSI 58 PFAS-certified) or carbon block (NSF/ANSI 53 PFAS-certified) at the drinking tap; same <20 ppt certification limit.
Lead	Point-of-use carbon block / pitcher certified for lead; Reverse osmosis	NSF/ANSI 53 (lead reduction) or 58	NO. Lead mostly enters from the home service line and plumbing after the point of entry, so a whole-house filter does not address it; use a certified point-of-use filter at the tap.	Choose a filter certified to NSF/ANSI 53 for lead (EPA consumer tool).
Chlorine taste and odor (aesthetic)	Activated carbon (granular or block)	NSF/ANSI 42	YES for free chlorine taste/odor with sized carbon tank.	Yes.
Chloramine	Catalytic carbon	NSF/ANSI 42 (only if the product listing claims chloramine reduction)	YES if the product is listed for chloramine; ordinary carbon is less effective.	Yes if listed.
Nitrate / nitrite	Reverse osmosis; Anion exchange (nitrate-selective)	NSF/ANSI 58 (nitrate/nitrite reduction listing) or 53	LIMITED. Carbon does not remove nitrate; anion exchange can treat whole-house but needs resin regeneration and brine handling.	RO certified for nitrate/nitrite.
Arsenic	Reverse osmosis; Activated alumina / specialty media	NSF/ANSI 58 (pentavalent arsenic) or 53	LIMITED. Needs pre-oxidation (As III to As V) and specialty media; not an off-the-shelf carbon job.	RO certified for arsenic V.
Hardness (scale)	Ion-exchange water softener	NSF/ANSI 44	YES (this is what whole-house softeners are for).	n/a
Bacteria / viruses (private wells)	UV disinfection	NSF/ANSI 55	YES for microbial inactivation only, with clear (low turbidity) water. UV does nothing for chemicals.	Yes.
Disinfection byproducts (TTHM/HAA5)	Activated carbon	NSF/ANSI 53 (VOC/THM claim)	PARTIAL. Carbon can reduce THMs; check the certified claim.	Yes at the tap.
Pharmaceuticals, pesticides (trace organics)	Activated carbon	NSF/ANSI 401 (up to 15 listed compounds)	n/a - claims are product specific.	Yes if listed.

Two items are deliberately left out: lithium (no certified filter claim found) and KDF media (no authoritative source collected yet). Where there is no source, the site makes no claim.

Examples that match

Match the product to the contaminant: a whole-house carbon system for chlorine and sediment, a certified tap-level or reverse-osmosis unit for lead or PFAS, and a lab test before buying either.

A small checked shortlist

Shown as examples, not endorsements; no links or prices. Certification is specific to a model and cartridge: confirm on the NSF database or IAPMO R&T listings before buying.

iSpring WGB32B whole-house 3-stage filter (sediment + two carbon blocks)Whole-house (point of entry)Listing: 5-micron sediment stage plus two coconut-shell carbon-block stages; up to 15 GPM; 1-inch NPT connections. Aimed at chlorine, taste, odor, sediment, rust. The listing says the carbon was third-party tested to unnamed NSF/ANSI standards.Not a PFAS, lead or nitrate solution, and not a softener. Carbon media must be replaced on schedule.
Waterdrop G3P600 under-sink reverse osmosis systemReverse osmosis at one tapListing: certified to NSF/ANSI 58 (TDS), 42 and 372; PFOA/PFOS claims appear on a separate NSF/ANSI 53 listing for its carbon cartridge. Needs power.Check the IAPMO or NSF listing for this exact model and cartridge. Certified PFAS claims are to under 20 ppt combined, above the 4 ppt federal limit.
iSpring RCC7AK-BN 6-stage alkaline reverse osmosis systemReverse osmosis at one tapListing: system certified to NSF/ANSI 58; under-sink with storage tank, no power needed. The listing also states PFAS reduction of 96-99%.NSF lists contaminant claims under the -BN and -BLK variants and TDS only for the plain RCC7AK; confirm the exact model. The PFAS figure is a manufacturer claim, not a certified one.
ZeroWater ZD-010RP 10-cup filter pitcherPitcher at the tapListing: tested to NSF/ANSI 53 for lead and PFOA/PFOS (performance data sheet from IAPMO R&T). Pitcher, so drinking water only.Certified PFOA/PFOS reduction is to the standard's test level, not proof of 4 ppt. Replace the filter on schedule; no filter works past its rated life.
Pentair FreshPoint F2000-B2B 2-stage under-sink carbon filterUnder-sink carbon at one tapListing: certified by IAPMO R&T against NSF/ANSI 53 for PFOA/PFOS reduction; twin carbon-block cartridges with lead-reduction media; replace after 675 gallons or one year.Read the NSF listing for the exact cartridge and rated capacity; certified PFAS claims stop at under 20 ppt combined.
Tap Score Lead & Copper mail-in lab test kitTest kitListing: mail-in sampling kit analysed by EPA-certified labs; returns a report. Lead from household plumbing varies tap to tap, so a utility-wide number cannot replace this.Follow the first-draw sampling instructions in the kit.
Tap Score PFAS mail-in lab test kit (EPA Method 537.1)Test kitListing: 14 PFAS compounds incl. PFOA and PFOS by EPA Method 537.1; sampling vials and prepaid label included.Does not cover every PFAS (for example HFPO-DA/GenX is not in the 537.1 list); ask the lab which compounds it reports.
DOD Labs 25-analyte PFAS mail-in test kit (EPA Method 533 analytes)Test kitListing: 25 PFAS analytes by the process in EPA Method 533, including PFOA, PFOS, PFHxS, PFNA and HFPO-DA.Informational test; check the lab's reporting limits against the 4 ppt PFOA/PFOS level.

Whole-house brands such as Aquasana and SpringWell also sell point-of-entry systems; they are mentioned here for orientation only, with no link, and the same limits apply (they do not remove PFAS to 4 ppt on certification alone).

Sources

Not medical, legal or engineering advice. NSF/ANSI standards are paywalled; this page summarises NSF, ANSI and EPA descriptions of them.