Hexavalent chromium is recognized as a human carcinogen when it is inhaled. Chronic inhalation of hexavalent chromium has been shown to increase risk of lung cancer and may also damage the small capillaries in kidneys and intestines.
Other adverse health effects associated with hexavalent chromium 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.
Hexavalent Chromium: An Occupational Hazard
NIOSH considers all hexavalent chromium compounds to be potential occupational carcinogens. Many workers are exposed to hexavalent chromium during the production of stainless steel, chromate chemicals and chromate pigments. Hexavalent chromium exposure also occurs during work activities such as stainless-steel welding, thermal cutting and chrome plating.
Hexavalent Chromium in Drinking Water
The potentially adverse health effects of hexavalent chromium 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 hexavalent chromium in 31 of them (89 percent). Water samples in 25 of those cities contained hexavalent chromium 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 hexavalent chromium safe for human consumption. Rather, it underscored the lack of confirmed knowledge and clear guidelines concerning the level at which hexavalent chromium in drinking water becomes a public health hazard.
In September 2010, the EPA launched a reassessment of hexavalent chromium when it released a draft human health assessment that proposes classifying hexavalent chromium 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 hexavalent chromium 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 hexavalent chromium in drinking water.
Evidence of Adverse Health Effects from Hexavalent Chromium in Tap Water
There is very little evidence of hexavalent chromium in drinking water causing cancer or other adverse health effects in humans. Only a few animal studies have found a possible connection between hexavalent chromium in drinking water and cancer, and only when the laboratory animals were fed levels of hexavalent chromium that were hundreds of times greater than the current safety standards for human exposure. Concerning those studies, the National Toxicology Program has said that hexavalent chromium in drinking water shows "clear evidence of carcinogenic activity” in laboratory animals and increases the risk of gastrointestinal tumors.
The California Hexavalent Chromium Lawsuit
The most compelling case for human health problems caused by hexavalent chromium 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 hexavalent chromium 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 hexavalent chromium was used in cooling towers at the site to prevent corrosion. Wastewater from the cooling towers, containing hexavalent chromium, 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 were higher than normal, and how much of a danger the hexavalent chromium 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 hexavalent chromium-related claims in other California communities.