Boiling kills microbes and drives off chlorine and most volatile byproducts, but it does not remove lead, arsenic, nitrate, PFAS or fluoride; as water evaporates, their concentration rises. Rice takes up arsenic from cooking water; cooking in excess water and draining removes part of it. A boil-water notice is about germs, never about lead.
| Source | What it found (quoted) and its limits | Evidence |
|---|---|---|
| CDC. Lead — Tips: Water (archived page) (2017 (archived)) · new agency guidance · n = n/a |
"Boiling this water will NOT reduce the amount of lead in your water." "Water that comes out of the tap warm or hot can contain much higher levels of lead." "In all situations, drink or cook only with water that comes out of the tap cold." If header pipe has lead: "run high-volume taps (such as your shower) on COLD for 5 minutes or more" Route: ingestion-cooking. What reduces it: Cold-water flushing; NSF-certified lead filter or bottled water for drinking/cooking/formula where >15 ppb Limits: Archived version; current CDC page restructured |
Evidence: strong Free to read · source · added 2026-10-30 |
| US FDA. Seven Things Pregnant Women and Parents Need to Know About Arsenic in Rice and Rice Cereal (consumer update, archived) (2016 (archived 2022)) · new agency consumer guidance · n = n/a |
"cooking rice in excess water (from six to 10 parts water to one part rice), and draining the excess water" can "reduce from 40 to 60 percent of the inorganic arsenic content, depending on the type of rice"; "this method may also remove some key nutrients" Route: ingestion-cooking. What reduces it: Excess-water cooking with low-arsenic water Limits: Page silent on arsenic in the cooking water itself |
Evidence: strong Free to read · source · added 2026-10-30 |
| CDC. Arsenic and Drinking Water from Private Wells (archived fact sheet) (2008 (archived)) · new agency guidance · n = n/a |
"Boiling water will not remove arsenic" and "could slightly increase the concentration of arsenic in your water if you continue boiling and lose a large amount of water as steam." "Chlorine (bleach) disinfection will also not remove arsenic." Route: ingestion-cooking. What reduces it: Point-of-use RO, ultrafiltration, ion exchange, distillation Limits: Archived page |
Evidence: strong Free to read · source · added 2026-10-30 |
| Minnesota Dept of Health. PFAS — Home water treatment (web page) (2024) · new state agency guidance · n = n/a |
"Boiling water will not remove PFAS." "Filters containing activated carbon or reverse osmosis membranes have been shown to be effective at removing PFAS"; "look for products certified to NSF/ANSI 53 (for filters) or NSF/ANSI 58 (reverse osmosis)"; softeners and iron filters "do NOT remove PFAS"; RO "more practical as a point-of-use treatment option (not at point-of-entry)" Route: ingestion-cooking. What reduces it: POU GAC/RO at kitchen tap for drinking and cooking Limits: Certification standards (Apr 2024) do not yet track EPA 2024 MCLs |
Evidence: moderate Free to read · source · added 2026-10-30 |
| Pan W, Johnson ER, Giammar DE. Lead phosphate particles in tap water: challenges for point-of-use filters (ACS journal; NSF-funded) (2021 (approx.)) · new laboratory challenge tests of NSF/ANSI 53 faucet filters · n = 2 filter units, 190 L each |
With particulate lead phosphate at 150 μg Pb/L, pH 7, low ionic strength: "41% of the Pb passed through the POU filters"; 32% at 50 mM ionic strength; 17% with 0.5 mM Ca Route: ingestion-cooking (filters feeding taps/fridges). What reduces it: Certified lead filters work best on dissolved lead; flush and consider RO where particulate lead is likely Limits: Year/journal not on page; refrigerator/ice-maker filters not tested |
Evidence: moderate Free to read · source · added 2026-10-30 |
| Carey M, Jiujin X, Farias JG, Meharg AA. Rethinking rice preparation for highly efficient removal of inorganic arsenic using percolating cooking water. PLoS ONE 10(7):e0131608 (2015) · new laboratory cooking experiments · n = 12 rice samples |
Coffee percolator with tap water: "49±7% of Asi could be removed across all 12 samples" ("up to 85% removal observed for one sample"); "At a water-to-rice cooking ratio of 12:1, 57±5% of Asi could be removed"; 3:1 and 6:1 ratios 29%; when cooking water is high in arsenic "cooking further elevates the arsenic content of the cooked product" Route: ingestion-cooking. What reduces it: Excess low-arsenic water, drained; absorbed-water (rice-cooker) method removes none Limits: Lab study; nutrient loss not assessed |
Evidence: moderate Free to read · source · added 2026-10-30 |
| Carrasco-Turigas G, Villanueva CM, Goñi F, Rantakokko P, Nieuwenhuijsen MJ. The effect of different boiling and filtering devices on the concentration of disinfection by-products in tap water. J Environ Public Health 2013:959480 (2013) · new laboratory experiment on Barcelona tap water · n = replicate experiments |
Total THM4 change: kettle −48%, saucepan −66%, microwave −97% (chloroform −69% / −78% / −84%); reverse osmosis −97%; new pitcher filter −89%, aged to 150 L −74% Route: ingestion-cooking. What reduces it: Boiling removes most volatile THMs (not non-volatile DBPs); RO or carbon pitcher also effective Limits: One city's water; HAAs not measured |
Evidence: moderate Free to read · source · added 2026-10-30 |
| Bae M et al. Arsenic in cooked rice in Bangladesh. Lancet 360:1839-1840 (2002) · new on-site cooking experiment · n = not in abstract |
"The concentration of arsenic in cooked rice was higher than that in raw rice and absorbed water combined," "suggesting a chelating effect by rice grains, or concentration of arsenic" "because of water evaporation during cooking, or both." Route: ingestion-cooking. What reduces it: Do not cook rice/pasta in arsenic-contaminated water; use treated water Limits: Bangladesh well water (very high As); abstract-only; no numeric uptake |
Evidence: moderate Paywalled · source · added 2026-10-30 |
| Oregon Health Authority. Nitrate in drinking water (health fact sheet) (current) · new state agency guidance · n = n/a |
Boiling "does not remove nitrate and can increase nitrate levels"; above 10 mg/L do not give to babies under six months or use to mix formula; "Several treatment methods can remove nitrate from drinking water, including ion exchange and reverse osmosis" Route: ingestion-cooking. What reduces it: RO/ion exchange/distillation; never boil to 'purify' nitrate water for infants Limits: State summary |
Evidence: moderate Free to read · source · added 2026-10-30 |
Evidence grade: strong = trials, large field studies or official datasets; moderate = smaller or lab studies with real water; weak = single small studies, makers' specs or secondary reports. "Free to read" means the source itself is free to read online.