Chloride
Cities measured
87
Detected in
87 / 87
EU limit
250 mg/L
Highest
242 mg/L — Abu Dhabi
Overview
Chloride is a naturally occurring anion in virtually all water bodies. Sources include geological dissolution, road salt (NaCl), sewage effluent, and coastal seawater influence. In combination with low pH, chloride accelerates lead leaching from pipes.
Health Relevance
At drinking water concentrations, chloride poses no direct health risk. Very high chloride (> 250 mg/L) is corrosive to metal infrastructure and gives water a salty taste.
Regulatory Limits
Drinking Water Directive 2020/2184
250 mg/L (indicator — taste and corrosion threshold).
Controversy & Contested Science
Winter road salting has raised chloride in Northern European and North American freshwater bodies by 5–10× since the 1940s. A 2022 paper in Science found 37% of North American lakes exceeded safe thresholds for aquatic life. The 'freshwater salinisation crisis' has no cost-effective technical remedy at scale — reducing road salt faces resistance from highway safety advocates, and chloride cannot be cost-effectively removed from drinking water once present in source water.