178Chromium is an odorless and tasteless metallic element. Chromium is found naturally in rocks,
plants, soil and volcanic dust, humans and animals. The most common forms of chromium that
occur in natural waters in the environment are trivalent chromium (chromium-3), and hexavalent
chromium (chromium-6).
Chromium-3 is an essential human dietary element and occurs naturally in many vegetables, fruits,
meats, grains and yeast. Chromium-6 occurs naturally in the environment from the erosion of
natural chromium deposits but it can also be produced by industrial processes. There are
demonstrated instances of chromium being released to the environment by leakage, poor storage,
or inadequate industrial waste disposal practices.
What are some uses for Chromium?
Metallic chromium is used mainly for making steel and other alloys. Chromium compounds in either
the chromium-3 or chromium-6 forms are used for chrome plating, dyes and pigments, leather and
wood preservation.
What are Chromium's Health Effects?
Chromium-3 is a nutritionally essential element in humans and is often added to vitamins as a
dietary supplement. Chromium-3 has relatively low toxicity and would be a concern in drinking
water only at very high levels of contamination; Chromium-6 is more toxic and poses potential
health risks. People who use water containing total chromium in excess of the maximum
contaminant level (MCL) over many years could experience allergic dermatitis.
EPA proposed to classify chromium-6 as likely to be carcinogenic to humans when ingested. The
Agency continues to work towards completing the human health assessment and making a final
determination about the carcinogenicity of chromium-6. When the assessment is completed, EPA
will determine whether the drinking water standard for total chromium needs to be revised.
What are EPA's drinking water regulations for Chromium?
The Safe Drinking Water Act requires EPA to determine the level of contaminants in drinking water
at which no adverse health effects are likely to occur. These non-enforceable health goals, based
on possible health risks from exposure over a lifetime are called maximum contaminant level goals
(MCLG).
The MCLG for total chromium is 0.1 mg/L or 100 parts per billion (ppb). EPA has set this level of
protection based on the best available science at the time the rule was promulgated. EPA has set
an enforceable regulation for total chromium, called a maximum contaminant level (MCL), at 0.1
mg/L or 100 ppb. MCLs are set as close to the health goals as possible, considering cost, benefits
and the ability of public water systems to detect and remove contaminants using suitable treatment
technologies.
In this case, the MCL equals the MCLG, because analytical methods or treatment technology do
not pose any limitation. States may set more stringent drinking water MCLGs and MCLs for total
chromium than EPA.
Why are Chromium-6 and Chromium-3 covered in the same Standard?
Chromium-6 and chromium-3 are covered under the total chromium drinking water standard
because these forms of chromium can convert back and forth in water and in the human body,
depending on environmental conditions.