WHO 2022 — Guidelines for drinking-water quality, fourth edition incorporating the first and second addenda
The fourth edition of the WHO Guidelines for drinking-water quality (GDWQ), consolidated in 2022 to incorporate the first (2017) and second (2022) addenda, is the global reference framework for drinking-water safety and the parent document under which WHO publishes background documents for each individual chemical and microbial parameter. The chemical fact sheets (Chapter 12) and the consolidated summary tables (Annex 3) carry health-based guideline values for the substances of concern in drinking-water, including all ten of the HMI analyte panel except inorganic tin; the framework is implemented through water safety plans (Chapters 2 and 4) and surveillance arrangements (Chapter 5). For HMI, the load-bearing rows are the guideline values for lead (provisional, 10 µg/L), arsenic (provisional, 10 µg/L), cadmium (3 µg/L), chromium (50 µg/L for total Cr), nickel (70 µg/L), inorganic mercury (6 µg/L), uranium (provisional, 30 µg/L) and antimony (20 µg/L), together with the explicit decisions not to set health-based guideline values for aluminium (instead specifying coagulation-performance targets of 0.1 mg/L for large facilities and 0.2 mg/L for small facilities) and inorganic tin (occurrence well below health concern).
Key numbers
Health-based and provisional guideline values for HMI-panel metals (Annex 3, Table A3.3, p. 525–527; cross-checked against Chapter 12 fact sheets):
| Metal / species | Guideline value (mg/L) | Guideline value (µg/L) | Designation | Basis (fact-sheet page) |
|---|---|---|---|---|
| Antimony (Sb) | 0.02 | 20 | Health-based GV | TDI 6 µg/kg bw, NOAEL 6.0 mg/kg bw/day, UF 1000 (p. 339) |
| Arsenic (total As) | 0.01 | 10 | Provisional (A, T) | Treatment performance and analytical achievability; PTWI withdrawn (p. 340–343) |
| Cadmium (Cd) | 0.003 | 3 | Health-based GV | PTMI 25 µg/kg bw; 10% allocation to water (p. 354) |
| Chromium (total Cr) | 0.05 | 50 | Health-based GV (2020 update) | Small-intestine hyperplasia, threshold MoA for Cr(VI); chromium(VI) classified IARC Group 1 by inhalation; total Cr basis because of speciation limits (p. 367–368) |
| Lead (Pb) | 0.01 | 10 | Provisional (A, T) | Maintained on treatment performance and analytical achievability after JECFA PTWI withdrawal; no threshold for critical effects (p. 415–417) |
| Mercury, inorganic (Hg²⁺) | 0.006 | 6 | Health-based GV | TDI 2 µg/kg bw, NOAEL 0.23 mg/kg bw/day rat kidney effects; does not apply to methylmercury (p. 426) |
| Nickel (Ni) | 0.07 | 70 | Health-based GV (2021 update) | Reproductive toxicity (post-implantation loss), BMDL₁₀ 1.3 mg/kg bw/day, TDI 13 µg/kg bw, UF 100; also protective against systemic contact dermatitis (p. 436–437) |
| Uranium (U) | 0.03 | 30 | Provisional (P) | Nephritis as critical chemical endpoint; TDI 60 µg/day from Finnish epidemiology; chemical not radiological aspects (p. 479) |
| Aluminium (Al) | — | (0.1 / 0.2)* | No GV — performance levels | JECFA PTWI 1 mg/kg bw would yield 0.9 mg/L HBV, but practicable coagulation-process performance dictates ≤0.1 mg/L (large facilities) and ≤0.2 mg/L (small facilities) in finished water (p. 333–335) |
| Inorganic tin (Sn) | — | — | No GV established | Levels in drinking-water typically 1–2 µg/L; chronic toxicity threshold ≈200 mg/kg in food, JECFA PTWI 14 mg/kg bw; not deemed a hazard at drinking-water concentrations (p. 412–413) |
* For aluminium, the table value is a practicable performance target, not a health-based guideline value.
Designation codes (Table A3.3 footnote): A = provisional guideline value because the calculated guideline value is below the achievable quantification level; T = provisional because the calculated guideline value is below the level achievable through practical treatment methods; P = provisional guideline value because of uncertainties in the health database. The “10 µg/L (A, T)” designation that arsenic and lead share reflects both achievability constraints.
Adjacent metals also covered by the GDWQ that lie outside the HMI ten-analyte panel but inform drinking-water exposure (Annex 3, Table A3.3):
| Metal | Guideline value | Notes |
|---|---|---|
| Barium | 1.3 mg/L (1 300 µg/L) | Health-based (p. 346) |
| Copper | 2 mg/L (2 000 µg/L) | Acute GI effects; staining of laundry below GV (p. 369–370) |
| Manganese | 0.08 mg/L (80 µg/L) (P) | Provisional; total Mn; aesthetic and health basis (2021 update) |
| Selenium | 0.04 mg/L (40 µg/L) (P) | Provisional |
Per-metal toxicology references used to set the guideline values (Chapter 12 fact sheets):
| Metal | Critical endpoint | TDI / PTMI / PTWI | Allocation to water | Adult body weight / consumption assumption |
|---|---|---|---|---|
| Sb | Reduced body weight gain and food/water intake (90-day rat, K antimony tartrate) | TDI 6 µg/kg bw | 10% | 60 kg, 2 L/day |
| As | Bladder, lung and skin cancer in arsenic-endemic populations; PTWI withdrawn | — (GV is achievability-based) | 20% (previous derivation) | 60 kg, 2 L/day |
| Cd | β₂-microglobulinuria in adults ≥50 y (JECFA 2011) | PTMI 25 µg/kg bw | 10% | 60 kg, 2 L/day |
| Cr | Small-intestinal hyperplasia (NTP rodent bioassays) | — (achievability and toxicology) | — | 60 kg, 2 L/day |
| Pb | No threshold for neurodevelopmental, cardiovascular, renal effects; JECFA PTWI withdrawn | — (GV is achievability-based) | — | 60 kg, 2 L/day |
| Hg (inorganic) | Renal effects in 26-week rat study, NOAEL 0.23 mg/kg bw/day | TDI 2 µg/kg bw | 10% | 60 kg, 2 L/day |
| Ni | Post-implantation loss in two-generation rat reproductive study; BMDL₁₀ 1.3 mg/kg bw/day | TDI 13 µg/kg bw | 20% | 60 kg, 2 L/day |
| U | Nephritis; lower 95% CI of 95th-percentile Finnish exposure distribution | TDI 60 µg/day | (single source, no fractional allocation cited) | 60 kg, 2 L/day |
| Al | Neurotoxicity (PTWI basis); coagulation performance binds | PTWI 1 mg/kg bw (JECFA 2007) | 20% (would-be HBV) | 60 kg, 2 L/day |
Occurrence in drinking-water as reported in the fact sheets (representative values, not site-specific):
| Metal | Reported drinking-water occurrence |
|---|---|
| Sb | Surface water <0.2 µg/L; drinking-water generally <5 µg/L |
| As | Natural waters 1–2 µg/L; in arsenic-affected groundwater up to ~12 mg/L documented |
| Cd | Drinking-water usually <1 µg/L |
| Cr | Total Cr in drinking-water usually <5 µg/L |
| Pb | Generally <5 µg/L; >100 µg/L where lead service lines or fittings are present; primary source is plumbing, not raw water |
| Hg (inorganic) | Surface and ground water usually <0.5 µg/L |
| Ni | Drinking-water typically <25 µg/L; up to 5 mg/L where Ni-containing fittings leach |
| U | Drinking-water generally <1 µg/L; up to 700 µg/L documented in some private supplies |
| Al | Variable; depends on coagulation-process control |
| Sn | 1–2 µg/L typical; >1–2 µg/L exceptional in drinking-water |
Analytical achievability (limits of detection and quantification quoted in the fact sheets):
| Metal | Practical LOD by best technique |
|---|---|
| Sb | 0.1–1 µg/L (electrothermal AAS); 0.1 µg/L (ICP-MS) |
| As | 0.1 µg/L (ICP-MS); 2 µg/L (hydride generation AAS or flame AAS); practical quantification limit 1–10 µg/L |
| Cd | 0.01 µg/L (ICP-MS); 2 µg/L (flame AAS) |
| Cr (total) | 0.08–7 µg/L (ICP-AES/ICP-MS/AES/graphite furnace AAS); 0.5 mg/L (flame AAS) |
| Cr(VI) by ion chromatography | 0.0044–0.015 µg/L |
| Pb | 1 µg/L (AAS); practical quantification limit 1–10 µg/L |
| Hg (inorganic) | 0.05 µg/L (cold-vapour AAS); 0.6 µg/L (ICP); 5 µg/L (flame AAS) |
| Ni | 0.5–5 µg/L (ICP-MS/ICP-AES/graphite furnace AAS); 0.1 mg/L (flame AAS) |
| U | 0.01 µg/L (ICP-MS); 0.1 µg/L (laser/UV fluorimetry); 0.2 µg/L (ICP with adsorption chelating resin) |
Methods (brief)
Guideline values are derived by the WHO drinking-water quality framework set out in Chapter 8 (Chemical aspects). Two derivation pathways are used: (1) for threshold chemicals, calculate a health-based value from a tolerable daily intake (TDI), tolerable monthly intake (PTMI) or tolerable weekly intake (PTWI), an allocation fraction to drinking-water (typically 10%–20%, occasionally 1% for compounds where food is the dominant exposure route), a default 60 kg adult body weight, and a default 2 L/day water consumption; (2) for non-threshold (genotoxic carcinogen) chemicals, calculate the concentration associated with an upper-bound excess lifetime cancer risk of 10⁻⁵ (one additional cancer per 100 000 of population over 70 years). Provisional guideline values are designated where the calculated value is below practical treatment-process performance or analytical-quantification capability (codes A and T) or where the underlying health database carries material uncertainty (code P).
The 2022 consolidated volume incorporates the first addendum (2017) and second addendum (2022), pulling forward the updated risk assessments for chromium (2020), nickel (2021) and manganese (2021), together with refreshed cyanobacterial-toxin reference values (anatoxins, cylindrospermopsins, microcystins, saxitoxins). Background documents for individual chemicals (Annex 2 reference list, pp. 511–519) are the source of the line-level toxicology; the fact sheets in Chapter 12 are summary derivations of those background documents.
For HMI-relevant analytes, the document’s stance on speciation is explicit: arsenic is treated as total inorganic-plus-organic for the GV (with the toxicology dominated by inorganic species and ~25% of dietary intake assumed inorganic); mercury’s GV applies only to inorganic mercury (Hg²⁺), with methylmercury handled by food-borne assessments and not by drinking-water; chromium’s GV is for total Cr because routine speciation between Cr(III) and Cr(VI) is not yet reliably achievable in drinking-water analysis. Aluminium and inorganic tin are explicitly given no guideline value, but for different reasons — Al is constrained by coagulation-performance rather than calculated HBV, while Sn occurs below health concern.
Implications
Certification: This is the parent reference for drinking-water guideline values across the HMI panel. HMTc product categories that touch reconstituted drinking-water — most directly bottled drinking-water and powdered infant formulas reconstituted with tap water — should anchor literature-baseline rows to these values where the matrix is drinking-water itself, then apply the row’s native-basis conversion for products evaluated as-consumed. The provisional designations on Pb, As and U are load-bearing: WHO explicitly maintains these values at treatment-and-analytics achievability, not health-based bottoms, so any HMTc threshold tighter than the WHO GV moves with the literature, not against it. The Al non-GV is also load-bearing because it shows the WHO framework is willing to depart from the JECFA-derived HBV when treatment performance binds — a precedent HMTc may invoke when feasibility binds in product matrices.
Courses: Useful for brand QA, regulatory affairs, and supply-chain courses. The fact-sheet structure (occurrence, basis of derivation, LOD, treatment performance, allocation) is the canonical template for teaching how guideline values are constructed and how health-based versus achievability-based designations differ.
App: The drinking-water guideline values feed the contamination_profile baseline for water for Pb, Cd, As (iAs+tAs), Cr, Ni, Hg-inorganic, U, Sb, and the no-GV decision feeds the same profile for Al and Sn. The values are matrix-specific (drinking-water) and should not be propagated as default per-mass thresholds onto food matrices.
Microbiome: Not addressed in this volume in a way that is directly relevant to the HMI–WikiBiome federation; the GDWQ is overwhelmingly about chemical and microbial drinking-water safety, not metal–microbiome interaction.
Limitations
This is a synthesis-and-policy document, not a primary occurrence study. The numerical values in this source are derivations from underlying toxicology and exposure databases, not pooled measurements with a single sample size. The PTWI for lead and arsenic was withdrawn during the period this 4th-edition consolidation spans, but the GVs were maintained at the prior values on achievability grounds; that means the Pb and As GVs in this document are not health-based and should not be cited as if they were. The Cr GV is for total Cr only and does not address Cr(VI) separately, although the toxicology is dominated by Cr(VI); the WHO 2020 reassessment identifies an intestinal threshold MoA and concludes Cr-VI carcinogenicity by ingestion is not supported by current data, which is a stronger conclusion than some other agencies hold. The Hg GV applies only to inorganic mercury and does not constrain methylmercury exposure, which is dominated by fish and not by drinking-water. The Al non-GV decision is constrained by coagulation-process realities, not toxicology — a fact-pattern that future WHO revisions could change if treatment performance improves.
Wiki pages updated on ingest
Verification notes
- Fresh ingest (no prior wiki source page existed; DOI/raw_handle/cite-key identity checks all returned zero hits on 2026-06-03).
- Cite-key chosen as
who-gdwq-2022-fourth-editionto mirror the existing WHO-prefixed slug convention (who-gemsfood-heavy-metal-contaminants,who-gems-food-database) and explicitly carry the year/edition. - Mercury appears in
metals:astHgonly. The WHO GV is explicitly for inorganic Hg²⁺ (which is a subset of tHg) and is explicitly NOT for methylmercury, soMeHgis correctly absent. - Arsenic appears as both
iAsandtAsbecause the WHO fact sheet derives the GV on the total-As basis (noting that toxicology is inorganic-dominated and ~25% of dietary intake is inorganic) and is enforceable as total arsenic at the tap. - Chromium appears as
Cr(notCr-VI) because the WHO GV is for total Cr; the document discusses Cr(VI) toxicology but does not set a Cr-VI-specific value. - Sb is included per CLAUDE.md Part 14 (HMI carries antimony as a recognized metal even though it is not in the certification ten-analyte panel).
- No new ingredient or product pages proposed; all slugs used (
ingredients/water,ingredients/breastmilk,products/bottled-drinking-water,products/infant-formula-powder-non-soy,products/infant-formula-powder-soy-based) exist in the current taxonomy. - No-near-duplicate flag: the trailing-”2” file in the June 3 Folder is byte-identical to
9789240045064-eng.pdf(both 5 321 705 bytes) and the SHA-256 above is the canonical hash for this ingest; the near_duplicates field records the alternate filename. - Brand firewall (Part 12): no brand names in source-page content. The WHO document itself names no brands.
- Wiki/HMTc firewall (Part 2): synthesis claims kept to single-paper scope (this WHO volume’s own derivations) without comparing to other agencies’ values; the Implications section names what HMTc may anchor but proposes no threshold values.
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.
| Commit | Date | Description |
|---|---|---|
| 1476f44 | 2026-06-09 | ingest: cacic2019-hemp-heavy-metals fresh from MFK/June 9 |