Chromium
Cities measured
87
Detected in
87 / 87
EU limit
25 μg/L
Highest
8.2 μg/L — Karachi
Overview
Chromium exists in multiple oxidation states. Trivalent (Cr³⁺) is an essential trace nutrient. Hexavalent (Cr⁶⁺) is a potent carcinogen. In water, Cr⁶⁺ sources include industrial discharge from electroplating and tanning, and historically from chromate corrosion inhibitors used in US public water systems.
Health Relevance
Hexavalent chromium is classified as a Group 1 carcinogen (IARC) — causing lung cancer via inhalation and stomach cancer and kidney damage via ingestion. Trivalent chromium is not a health concern at typical concentrations.
Regulatory Limits
Drinking Water Directive 2020/2184
50 μg/L (total chromium). A specific Cr⁶⁺ limit is under consideration.
Controversy & Contested Science
The Erin Brockovich case (PG&E vs. Hinkley, California) — the 2000 film — involved Cr⁶⁺ groundwater contamination from industrial cooling towers. The $333M settlement was the largest direct-action lawsuit in US history. However, a 2010 independent reanalysis found no clear cancer cluster in Hinkley — raising questions about the film's narrative. California's proposed Cr⁶⁺ public health goal of 0.02 μg/L sits 5,000× below the EPA's 100 μg/L limit — illustrating the vast gap between science-based precautionary limits and feasibility-constrained regulatory maxima.