Explain what NSF/ANSI Standards 44, 53, 58, and 401 each certify, and how to verify a manufacturer's claim against one

Steps

1. NSF/ANSI 44 certifies cation-exchange water softeners: reduction of hardness (calcium/magnesium) by exchange for sodium or potassium ions; verify a claim by checking the softener model's listing for 'NSF/ANSI 44' plus its rated capacity/grain rating.
2. NSF/ANSI 53 certifies health-effects contaminant reduction (50+ possible individual claims, e.g., lead, cryptosporidium/cysts, VOCs) for point-of-use/point-of-entry systems; a product can be 53-certified for some contaminants but not others, so verify the specific contaminant claim, not just the standard number.
3. NSF/ANSI 58 certifies reverse-osmosis systems (membrane-based reduction of TDS and other contaminants); verify RO-specific performance claims against 58 rather than 53.
4. NSF/ANSI 401 certifies reduction of 'emerging contaminants' (pharmaceuticals, herbicides, and other compounds not yet EPA/Health Canada-regulated) for POU/POE systems; it layers on top of 42/53/58 rather than replacing them.
5. To verify any of these claims for a specific product, cross-check the manufacturer's marketing claim against the actual NSF (info.nsf.org / listings.nsf.org) or WQA (find.wqa.org) certified-product listing for that exact model.