WHO 2022 - Drinking-water quality guidelines
WHO’s fourth edition drinking-water guidelines, incorporating the first and second addenda, are the global reference source for drinking-water chemical guideline values. For the heavy-metal wiki, the useful data are the chemical guideline values, the provisional-value designations, the source categories, and the fact-sheet caveats that prevent species mixing. WHO lists arsenic and lead at 0.01 mg/L as provisional values because the calculated health-protective levels are below practical analytical or treatment achievability; manganese is a new provisional total-manganese value at 0.08 mg/L focused on bottle-fed infants; mercury is explicitly inorganic mercury; chromium is explicitly total chromium; and uranium is chemical toxicity only, not a radiological value.
Key numbers
WHO guideline values for HMI-relevant metals and metalloids:
| Constituent | WHO value (mg/L) | WHO value (ug/L) | Designation / basis | Important routing note |
|---|---|---|---|---|
| Antimony | 0.02 | 20 | Guideline value | Plumbing/fittings can be a source; form matters, but WHO table reports antimony generically |
| Arsenic | 0.01 | 10 | Provisional A,T | Drinking-water hazard is primarily inorganic arsenic; retained at 10 ug/L for analytical and treatment achievability |
| Barium | 1.3 | 1300 | Guideline value | Food is usually primary exposure, but groundwater can materially contribute |
| Cadmium | 0.003 | 3 | Guideline value | Food and smoking dominate exposure; galvanized materials and fittings can affect water |
| Chromium | 0.05 | 50 | Guideline value | WHO value is for total chromium because reliable water speciation remains difficult |
| Copper | 2 | 2000 | Guideline value | Intended to protect against acute gastrointestinal effects; taste/staining can occur below or near the value |
| Lead | 0.01 | 10 | Provisional A,T | No longer a health-based value; should be kept as low as reasonably practicable |
| Manganese | 0.08 | 80 | Provisional P | Total manganese; protective for neurological effects in bottle-fed infants |
| Mercury | 0.006 | 6 | Guideline value | Inorganic mercury only; not methylmercury and not total food mercury |
| Nickel | 0.07 | 70 | Guideline value | Retained at 70 ug/L although the 2021 assessment supports an 80 ug/L health-based value |
| Selenium | 0.04 | 40 | Provisional P | Reported as selenium in the annex table; no public selenium metal page exists yet |
| Uranium | 0.03 | 30 | Provisional P | Chemical toxicity only; radiological aspects are addressed separately |
Aluminium is handled differently:
| Aluminium value | Concentration | Notes |
|---|---|---|
| No formal WHO guideline value | - | WHO does not establish a formal guideline value because the health-based value exceeds practicable levels |
| Derived health-based value | 0.9 mg/L | Derived from the JECFA PTWI with 20% drinking-water allocation |
| Practical level, large water-treatment facilities | 0.1 mg/L or less | Based on optimizing aluminium-based coagulation |
| Practical level, small facilities | 0.2 mg/L or less | Recognizes operational difficulty in smaller systems |
Selected occurrence, treatment, and analytical notes from the fact sheets:
| Constituent | WHO occurrence / achievability note |
|---|---|
| Antimony | Groundwater usually below 0.001 ug/L, surface water below 0.2 ug/L, drinking water generally below 5 ug/L; conventional treatment does not remove antimony well, so material control matters |
| Arsenic | Natural waters are usually 1-2 ug/L but can reach 12 mg/L in affected areas; 10 ug/L is a more reasonable conventional-treatment expectation than 5 ug/L in many systems |
| Barium | Drinking water is generally below 100 ug/L, but groundwater-derived supplies can exceed 1 mg/L |
| Cadmium | Drinking-water levels are usually below 1 ug/L; 0.002 mg/L should be achievable using coagulation or precipitation softening |
| Chromium | Total chromium in drinking water is usually below 5 ug/L; the guideline is for total chromium because validated speciation methods remain difficult |
| Copper | Running or flushed water can be low, while standing or partially flushed water can exceed 1 mg/L and sometimes much higher; corrosion of copper plumbing is the primary source |
| Lead | Drinking water is generally below 5 ug/L but can exceed 100 ug/L where lead service connections or fittings are present; sampling should be at the tap |
| Manganese | Fresh waters typically range 1-200 ug/L; treated drinking water is typically below 50 ug/L, but acidic groundwater can reach 10 mg/L |
| Mercury | Inorganic mercury in surface water and groundwater is usually below 0.5 ug/L; treatment of non-grossly contaminated raw water should be able to get below 1 ug/L |
| Nickel | Drinking water is typically below 25 ug/L but can reach 5 mg/L where alloys, taps, anthropogenic sources, or natural deposits mobilize nickel |
| Uranium | Drinking water is generally below 1 ug/L, but private supplies as high as 700 ug/L have been measured; conventional treatment can achieve about 1 ug/L in some settings |
Methods (brief)
This is a WHO guideline compendium, not a single occurrence survey. WHO derives guideline values from human and animal toxicology, exposure allocation assumptions, analytical quantification limits, treatment achievability, source-control practicality, and competing public-health risks such as maintaining disinfection. Formal guideline values are intended as concentrations that do not result in significant health risk over a lifetime of consumption unless a shorter exposure basis is specified. Provisional values are marked when scientific uncertainty is high, when the calculated health-based value is below analytical quantification, when treatment/source control cannot practically reach the calculated value, or when disinfection needs can push concentrations above the calculated level.
The chemical tables separate naturally occurring chemicals, industrial/human-dwelling sources, agricultural chemicals, treatment chemicals, and materials in contact with drinking water. The fact sheets add occurrence ranges, analytical method limits, treatment performance, derivation assumptions, and assessment dates for individual chemicals. For heavy-metal routing, the most important method rule is species discipline: WHO’s chromium value is total chromium, mercury is inorganic mercury, manganese is total manganese, and uranium is chemical rather than radiological.
Implications
This source is a regulatory and risk-assessment comparator for drinking water, bottled drinking water, mineral water, and water as a formulation or reconstitution input. It is not a market occurrence dataset and should not be pooled with bottled-water survey results or food concentration distributions. The guideline values can anchor regulatory crosswalks and app-facing explanations of why water quality can matter for infant formula reconstitution, beverages, and other high-water-intake categories.
The lead, arsenic, and manganese entries are especially important for HMI because they are not simple “safe line” values. Lead is maintained at 10 ug/L because lower values are difficult to achieve through central conditioning and analytical/treatment constraints; WHO still says concentrations should be kept as low as reasonably practicable. Arsenic at 10 ug/L is likewise retained as a practical goal despite low-dose cancer uncertainty and JECFA withdrawal of the older PTWI. Manganese at 80 ug/L is explicitly framed around bottle-fed infants, so formula pages should treat water manganese as a reconstitution-matrix issue, not as a measured concentration in formula powder.
Wiki pages this source may touch
- aluminum
- antimony
- arsenic
- arsenic-total
- arsenic-inorganic
- barium
- cadmium
- chromium
- copper
- lead
- manganese
- mercury
- mercury-total
- nickel
- uranium
- water
- bottled-drinking-water
- mineral-water
Verification notes
- Read the full 614-page PDF text, with close checks on the title/citation pages, chapter 8 chemical derivation rules, Tables 8.9, 8.11, 8.16, 8.17, Annex 3 Table A3.3, and the aluminium, antimony, arsenic, barium, cadmium, chromium, copper, lead, manganese, mercury, nickel, and uranium fact sheets.
- No DOI is assigned. The official WHO publication page lists the document as a 21 March 2022 guideline, 614 pages, ISBN
978-92-4-004506-4; the PDF itself gives the same electronic ISBN and the suggested citation. - The source page intentionally uses
ug/Linstead of the PDF’s micro sign so the page remains ASCII-only. - The raw canonical file
raw/Manual Fetch Kimi /June 3 Folder/9789240045064-eng.pdfand duplicate fileraw/Manual Fetch Kimi /June 3 Folder/9789240045064-eng 2.pdfare byte-identical with SHA-256a0ac96fa5eac13e4a14f9fd77ea86440eda9349e04fb58e5a86bee9c06db93d0; the duplicate is recorded in the tracker as duplicate accounting rather than a second source. - Brand and manufacturer names are not part of this source page. WHO’s generic “products or services” disclaimer is not treated as product evidence.
Page history
The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.