WHO Guidelines for Potable Water Quality
The World Health Organization (WHO) Guidelines for Drinking-Water Quality (GDWQ) serve as the global authority for setting national regulations and safety standards to protect public health. The current framework is the Fourth Edition incorporating the first, second, and third addenda.
The Core Preventive Framework
- Health-Based Targets: Setting maximum allowable limits for microbial, chemical, physical, and radiological hazards based on scientific risk assessment.
- Water Safety Plans (WSPs): Systematic, proactive risk-management procedures across the supply chain from water source through treatment to the consumer.
- Independent Surveillance: Consistent government and third-party auditing to ensure WSPs work and national standards are met.
Key Water Quality Parameters & Guidelines
1. Microbial Hazards
Water must contain zero detected pathogenic organisms. E. coli or thermotolerant coliform bacteria must be completely absent (0 CFU per 100 mL sample).
2. Chemical Contaminants
| Chemical Contaminant | WHO Maximum Guideline Limit | Primary Health Risk |
|---|---|---|
| Arsenic (As) | 10 μg/L (0.01 mg/L) | Cancer, skin lesions |
| Lead (Pb) | 10 μg/L (0.01 mg/L) | Neurodevelopmental delays in children |
| Fluoride (F⁻) | 1500 μg/L (1.5 mg/L) | Dental and skeletal fluorosis |
| Chromium (Cr) | 50 μg/L (0.05 mg/L) | Toxicity, carcinogenicity |
| Nitrate (NO₃⁻) | 50 mg/L | Methemoglobinemia ("blue baby syndrome") |
| Uranium (U) | 30 μg/L (0.03 mg/L) | Nephrotoxicity (kidney damage) |
3. Radiological Risks
- Gross alpha activity: 0.5 Bq/L screening level.
- Gross beta activity: 1.0 Bq/L screening level.
4. Acceptability & Aesthetic Aspects
- Turbidity: Ideally below 1 NTU for effective chlorine disinfection; up to 5 NTU is described as visually acceptable.
- pH: Usually recommended between 6.5 and 8.5.
- Taste, Odour, Appearance: Free of objectionable tastes, smells, or noticeable discoloration.
Recent Framework Updates [September 2026]
- Cyanobacteria management and alert-level systems.
- Small water supplies and practical Sanitary Inspection Packages.
- Climate resilience for drought and flooding impacts on water treatment infrastructure.