The World Health Organization publishes guideline values for drinking-water quality. The table below lists some of the most commonly referenced parameters. Always consult the latest edition of the WHO Guidelines for Drinking-water Quality for full details.
| Parameter | WHO guideline value | Health / aesthetic concern |
|---|---|---|
| Arsenic | 0.01 mg/L | Carcinogenic |
| Fluoride | 1.5 mg/L | Dental/skeletal fluorosis |
| Lead | 0.01 mg/L | Neurotoxic, especially in children |
| Nitrate (as NO₃⁻) | 50 mg/L | Methemoglobinaemia (blue-baby syndrome) |
| Nitrite (as NO₂⁻) | 3 mg/L | Methemoglobinaemia |
| Total coliforms | Not detectable | Indicator of faecal contamination |
| E. coli | Not detectable | Faecal contamination indicator |
| Turbidity | Ideally <1 NTU | Disinfection effectiveness |
| pH | 6.5 – 8.5 | Corrosion and taste |
| Total dissolved solids | 1,000 mg/L (aesthetic) | Taste and palatability |
Reference: World Health Organization. Guidelines for Drinking-water Quality. Fourth edition and subsequent addenda.