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Hexavalent Chromium

To help PWS better understand the presence of this contaminant in their systems, UL now offers analysis of hexavalent chromium by EPA Method 218.6 revision 3.3. UL has invested in new state-of-the-art instrumentation to achieve an MRL of 0.02 μg/L and also offers a low-level testing option for total chromium of 0.1 μg/L by EPA Method 200.8.  Using these two analytical methods, UL is helping utilities better understand the impact of total chromium on formation of hexavalent chromium in their water system.

What is hexavalent chromium?

Chromium exists in the environment in one of three valence states:

  • Metal form (chromium-0)
  • Trivalent (chromium-3)
  • Hexavalent chromium (chromium-6)

The metal form occurs naturally in rocks, plants and soils and the trivalent form occurs naturally in vegetables, fruits, meats, grains and yeast and is considered a nutritionally essential element. Hexavalent chromium enters the environment primarily through industrial processes including the production of steel and metal alloys, chrome plating, dyes and pigments as well as leather and wood preservation and is a suspected carcinogen.

Monitoring for hexavalent chromium

Total chromium was first regulated in drinking water under the Safe Drinking Water Act (SDWA) in 1992 when a maximum contaminant limit (MCL) of 100 μg/L was set to protect against allergic dermatitis.

As suggested by a study published by the Environmental Working Group in December of 2010, hexavalent chromium may be more widespread in drinking water than previously understood. In January of 2011, the U.S. Environmental Protection Agency (EPA) published new recommendations for enhanced monitoring of hexavalent chromium in drinking water. The agency is strongly encouraging all public water systems (PWS) to consider monitoring for this contaminant on a quarterly basis at the following locations:

  • Untreated water at the intake / well
  • Entry points to the distribution system
  • Representative locations within the distribution system

Additional resources regarding hexavalent chromium