Phosphate
Cities measured
87
Detected in
87 / 87
Highest
0.28 mg/L — Cairo
Overview
Phosphate enters water from geological sources, detergents, and agricultural runoff. Stockholm Water deliberately adds orthophosphate to form a protective scale inside iron and lead pipes, reducing metal leaching — a process called corrosion inhibition.
Health Relevance
Phosphate at drinking water concentrations is not a direct health concern. It is an essential macronutrient. The phosphate added for corrosion control is at trace levels well below any health threshold.
Regulatory Limits
Drinking Water Directive 2020/2184
No EU regulatory limit for drinking water.
Controversy & Contested Science
The 2014–2019 Flint, Michigan water crisis — where switching source water disrupted an established phosphate corrosion film, causing catastrophic lead leaching — made orthophosphate dosing globally prominent. Some researchers argue it masks the underlying lead pipe problem rather than solving it, and that lead pipes must be physically replaced. The US EPA's revised Lead and Copper Rule now requires accelerated pipe replacement. In Europe, millions of lead service lines remain. Phosphate dosing buys time at low cost — but critics say it has been used for decades to defer a $300+ billion infrastructure replacement problem.