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So What Do the Measured Units Mean?
As analytical methods have improved, various compounds, including hexavalent chromium, are likely to be found at very low levels in many of our nation's lakes, rivers and streams. Current EPA standards for all types of chromium provide for a maximum contaminant limit of 100 parts per billion (ppb), with some States adopting a more stringent standard of 50 ppb of total chromium. To better illustrate the extremely low level concentrations of chromium in our drinking water supply, current contaminant limits of 100 parts per billion could be compared to:
- 100 seconds of time in 32 years
- 100 kernels of corn in a 45-foot high, 16-foot diameter silo
- 100 drops of liquid in a railroad tanker car
What is the City of Raleigh Doing?
EPA's Third Unregulated Contaminant Monitoring Rule (UCMR-3)
As recommended by EPA, the Raleigh Water undertook preliminary sampling for chromium-6 for both source water and finished (treated) water. Water distribution sampling locations coincided with lead and copper sampling locations and maximum residence times within the system. The following table presents the city's results for this voluntary testing.
Chromium-6 Data 2011 through 2015
- Finished water is water that has passed through all processes in a water treatment plant and is ready to be delivered to consumers.
- Raw water is intake water prior to any treatment or use.
As research evolves on this subject, the Raleigh Water will continue to monitor the results and will comply with all standards adopted through implementation of any new Federal and State regulations. Raleigh Water is committed to protecting public health and ensuring the safety of the drinking water for our customers in Raleigh and the surrounding communities of Garner, Knightdale, Rolesville, Wake Forest, Wendell and Zebulon.
Is My Water Safe?
Yes, your water is safe to drink! As noted above, chromium-6 is currently regulated as part of the 'total chromium' drinking water standard under the Federal Safe Drinking Water Act (SDWA). This standard addresses all forms of chromium, including chromium-6. The current drinking water standard sets the maximum contaminant level (MCL) of total chromium allowed in drinking water at 100 parts per billion (ppb), also equivalent to 100 micrograms per liter (ug/L).
- Water industry professionals are researching the occurrence of Hexavalent Chromium in drinking water supplies and are monitoring for the development of any new regulations from Federal or State agencies.
- The fact that a substance is detectable does not mean the substance is harmful to humans.
- While this metal may be detected at very low levels in source waters, people regularly consume or expose themselves to products containing this metal in much higher concentrations (i.e., chrome fixtures, metal pots and other chromed items around the home). The level in which they are found in source waters is very small in comparison.
- The EPA maintains an active program called the Contaminant Candidate List (CCL) to identify contaminants in public drinking water that warrant detailed study. The EPA is currently evaluating Hexavalent Chromium through this and other programs.
History of Chromium-6
Hexavalent chromium (also known as chromium-6) is currently a topic of national debate and research. As with other contaminants of concern, the U.S. Environmental Protection Agency (EPA) has begun a "rigorous and comprehensive review of the potential health effects" of ultra low level concentrations of chromium. Hexavalent chromium is one of 20 chemicals currently being reviewed by the EPA for possible further regulations. Chromium is a naturally occurring metallic element in the periodic table. It is odorless and tasteless. Chromium is found throughout nature, including in humans, other animals, plants, soils, volcanic dust and water. The three most common forms of chromium found are chromium (0), chromium-3 and chromium-6. The metal chromium or chromium (0) is used in the making of steel. Chromium-3 and chromium-6 are both used for chrome plating, dyes and tanning processes.