The EPA has set the MCL for total chromium at 100 ppb. This includes all forms of chromium (Cr-3 and Cr-6). The state of Nebraska adopted the standard. The regulation does not require differentiation between Cr-3 and Cr-6. The MCL is based on levels that may cause “allergic dermatitis.”
Research shows Cr-6 may cause an irritation at levels around 25-50 ppb and may have a cancer effect at levels in excess of 10 ppm (parts per million). One part per million is 1,000 parts per billion and corresponds to 1 minute in 2 years or 1 penny in $10 thousand.
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