Why doesn't the EPA require testing of chromium-6? Nearly all the chromium found in Madison drinking water occurs as chromium-6. These levels are well below the current regulatory limit of 100 ppb. The levels range from below detection to a little over 2 ppb and are relatively unchanged in the over thirty years of test results we have. What are the total chromium levels for Madison wells?Īll Madison wells are tested annually for total chromium. The agency plans to use this information to determine whether a regulatory limit specifically for chromium-6 should be established. The EPA has been collecting nationwide occurrence data for chromium-6 in drinking water. When the regulation was established, it was assumed that all chromium in drinking water was chromium-6 and the MCL of 100 ppb was protective of human health. ![]() The federal government regulates only total chromium and the maximum contaminant level (MCL) is 100 ug/L or 100 parts per billion (ppb). What is the current water quality standard for chromium?Ĭurrently, there is no federal or state regulation for chromium-6. For example, industrial releases of chromium-6 are often converted to chromium-3 after being deposited into the soil. Chromium 3 occurs naturally in food and is an essential dietary nutrient while chromium-6 is a more toxic form of chromium.Ĭhromium can transform from chromium-3 to chromium-6, and vice versa, depending on the physical and chemical environment. The sum of all chromium in a sample is called total chromium. What is the difference between total chromium, chromium-6, and chromium-3?Ĭhromium occurs in the environment and drinking water sources in two principal forms: trivalent chromium (chromium-3) and hexavalent chromium (chromium-6). Concentrations in groundwater monitoring wells in Hinckley have measured over 500 ppb. Wastewater from the station percolated into the groundwater, affecting an area approximately two miles long and nearly a mile wide. Hinckley, California residents were awarded a multi-million dollar settlement from Pacific Gas & Electric, a company that used chromium-6 to prevent rust in cooling tower water at its compressor station. The techniques and the methods for measuring chromium may have changed, but the concentrations have not.Ĭhromium-6 was the carcinogen made famous by the movie Erin Brockovich. Total chromium levels have been measured at Madison wells since at least the early 1970s, and the levels are relatively unchanged since that time. The chromium-6 found in Madison's water is likely naturally-occurring and has been present in the area's water for many generations. ![]() Have chromium levels in Madison water increased? 03 parts per billion, although most of the time it is not detected there at all. One has never shown detectable levels, and the other has shown trace levels of. Our wells nearest to known coal ash deposits on the Isthmus have some of the lowest levels of chromium-6 in the city. It's unlikely that coal ash is contaminating Madison's water with chromium-6. The statewide rate of stomach cancer is well below the national average (3.8 per 100,000 people) and Dane County has one of the lowest rates in the state (2.5 per 100,000 people).Ĭould coal ash dumped on the Isthmus decades ago be a source of the chromium-6? The level of chromium in our area's drinking water has remained steady at least since the 1970s, yet rates of stomach cancer in Madison have declined over the same period. ![]() How do our rates of stomach cancer compare to the rest of the state and nation? Right now, there is no federal regulatory standard for chromium-6, although the State of California has enacted its own regulatory limit of 10 ppb. It was recently found to also cause stomach cancer in laboratory mice and rats when they were exposed to extremely high levels in drinking water. Chromium-6 has been detected at low levels (less than 2 ppb) in 14 of Madison's 22 wells.Ĭhromium-6 is known to be a potent carcinogen when inhaled. Research conducted in collaboration with the Wisconsin Geological Survey strongly suggests a natural origin of the chromium-6 found in Madison’s drinking water it is not likely caused industrial pollution. It can occur naturally in the ground but may also enter drinking water sources via industrial pollution. What is chromium-6 and why is it in our water?Ĭhromium-6 is an element that is commonly found at low levels in drinking water. Our extensive testing confirms that we meet or exceed all federal and state drinking water standards. Madison water is routinely tested for more than 130 potential contaminants, including both regulated and unregulated substances.
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