Chromium-6 is recognized as a human carcinogen when it is inhaled. Chronic inhalation of chromium-6 has been shown to increase the risk of lung cancer and may also damage the small capillaries in kidneys and intestines.
Other adverse health effects associated with chromium-6 exposure, according to the National Institute for Occupational Safety and Health (NIOSH), include skin irritation or ulceration, allergic contact dermatitis, occupational asthma, nasal irritation and ulceration, perforated nasal septa, rhinitis, nosebleed, respiratory irritation, nasal cancer, sinus cancer, eye irritation and damage, perforated eardrums, kidney damage, liver damage, pulmonary congestion and edema, epigastric pain, and erosion and discoloration of one's teeth.
An Occupational Hazard
NIOSH considers all chromium-6 compounds to be potential occupational carcinogens. Many workers are exposed to chromium-6 during the production of stainless steel, chromate chemicals, and chromate pigments. Chromium-6 exposure also occurs during work activities such as stainless-steel welding, thermal cutting, and chrome plating.
Chromium-6 in Drinking Water
The potentially adverse health effects of chromium-6 in drinking water have become an issue of growing concern nationwide. In 2010, the Environmental Working Group (EWG) tested tap water in 35 U.S. cities and found chromium-6 in 31 of them (89 percent). Water samples in 25 of those cities contained chromium-6 at concentrations higher than the "safe maximum" (0.06 parts per billion) proposed by California regulators, but far below the safety standard of 100 ppb for all types of chromium combined that was established by the U.S. Environmental Protection Agency (EPA).
That doesn't mean the EPA was declaring drinking water with a chromium-6 safe for human consumption. Rather, it underscored the lack of confirmed knowledge and clear guidelines concerning the level at which chromium-6 in drinking water becomes a public health hazard.
In September 2010, the EPA launched a reassessment of chromium-6 when it released a draft human health assessment that proposes classifying chromium-6 as a likely carcinogenic to humans who ingest it. The EPA expects to complete the health-risk assessment and make a final determination about the cancer-causing potential of chromium-6 through ingestion in 2011 and will use the results to determine whether a new safety standard is needed. As of December 2010, the EPA has not established a safety standard for chromium-6 in drinking water.
Evidence of Adverse Health Effects From Chromium-6 in Tap Water
There is very little evidence of chromium-6 in drinking water causing cancer or other adverse health effects in humans. Only a few animal studies have found a possible connection between chromium-6 in drinking water and cancer, and only when the laboratory animals were fed levels of chromium-6 that were hundreds of times greater than the current safety standards for human exposure. Concerning those studies, the National Toxicology Program has said that chromium-6 in drinking water shows "clear evidence of carcinogenic activity” in laboratory animals and increases the risk of gastrointestinal tumors.
The California Chromium-6 Lawsuit
The most compelling case for human health problems caused by chromium-6 in drinking water is the lawsuit that inspired the film, "Erin Brockovich," starring Julia Roberts. The lawsuit alleged that Pacific Gas & Electric (PG&E) had contaminated groundwater with chromium-6 in the California town of Hinkley, leading to a high number of cancer cases.
PG&E operates a compressor station for natural gas pipelines at Hinkley, and chromium-6 was used in cooling towers at the site to prevent corrosion. Wastewater from the cooling towers, containing chromium-6, was discharged into unlined ponds and seeped into the groundwater and contaminated the town's drinking water.
Although there was some question whether the number of cancer cases in Hinkley was higher than normal, and how much of a danger the chromium-6 actually posed, the case was settled in 1996 for $333 million-the largest settlement ever paid in a direct-action lawsuit in U.S. history. PG&E later paid nearly as much to settle additional chromium-6-related claims in other California communities.