By Rebecca Sutton, PhD, EWG Senior Scientist
When you see news reports about a cancer-causing chemical in drinking water everywhere you turn, you probably have a few questions. Of course you can read EWG's full report, but on the off chance you're pressed for time and just want to know the basics, we put together these 11 questions and answers.
1. What is hexavalent chromium?
Hexavalent chromium (or chromium-6) is a highly toxic form of the naturally occurring metal chromium. It is a well-known human carcinogen when inhaled, and recent evidence indicates it can cause stomach or gastrointestinal cancer when ingested in drinking water. However, a different form, trivalent chromium, is an essential nutrient.
People typically are exposed to chromium-6 by consuming contaminated water or food, and in some workplaces by breathing contaminated air. That's a concern especially for those working in metallurgy or leather-tanning facilities. Ingesting or inhaling contaminated soil particles may also be a source of exposure. Widespread industrial use has led to detections of hexavalent chromium in two-thirds of current or former Superfund toxic waste sites.
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2. How does it get into tap water?
Chromium-6 can get into water as a result of industrial contamination from manufacturing facilities, including electroplating factories, leather tanneries and textile manufacturing facilities, or from disposal of fluids used before 1990 in cooling towers. It also occurs naturally in some minerals. The widely used tap water disinfectant chlorine can transform trivalent chromium into the toxic hexavalent form.
3. Why is it a problem?
Exposure in tap water has been linked to cancers of the stomach and gastrointestinal tract in both animals and people. California's Environmental Protection Agency has issued a draft public health goal based on the conclusion that levels of chromium-6 greater than 0.06 parts per billion (ppb) in tap water may increase cancer risk.
Some people may be especially susceptible. Fetuses, infants and children are more sensitive to carcinogenic chemicals. In addition, people with less acidic stomachs appear to have a limited ability to convert chromium-6 to the benign trivalent form (chromium-3), putting them at greater risk. Using common antacids and proton pump inhibitors can lower stomach acidity. Other conditions that can inhibit stomach acid production include infection with Helicobacter pylori (a common bacterium linked to ulcers), pernicious anemia, pancreatic tumors, mucolipidosis type IV and some autoimmune diseases.
4. How can I find out if my tap water has hexavalent chromium in it?
California requires water utilities to test and report levels of chromium-6 in their water. For Californians, this is a good way to find out if this contaminant is a concern in your area. Unfortunately, these tests only measure levels at or above 1 ppb, more than 16 times above the suggested public health goal of 0.06 ppb.
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Of the 438 community water sources in California that have provided test data to EWG, 223 detected levels above 1 ppb, and 93 detected levels above 5 ppb. This means more than 13.7 million Californians drink tap water contaminated with chromium-6.
Elsewhere, water utilities only test and report levels of total chromium -- which includes both the toxic form and the essential nutrient chromium-3. Moreover, these tests only detect levels at or above 10 ppb, more than 160 times higher than California's proposed public health goal. If your tap water has detectable levels of total chromium, it's quite possible that it has levels of hexavalent chromium that exceed California's suggested public health goal. The ratio of chromium-3 to chromium-6 varies in different water supplies, so it is difficult to estimate how much of each might be in your water.
Contact your local water utility or check EWG's tap water database to learn if chromium has been detected in your tap water.
5. My tap water has high levels of chromium-6. What should I do?
If your tap water contains high levels, your best bet is to install a reverse osmosis filter certified to remove it. Reverse osmosis filters, especially when combined with superior carbon filter technology, are the best way to remove the largest number of contaminants.
EWG assembled a list of reverse osmosis water filters certified to remove hexavalent chromium and available for purchase on Amazon.com.
See EWG's water filter buying guide for more information on how to choose a water filter.
While drinking bottled water might seem like a good way to avoid exposing yourself to hexavalent chromium in tap water, there is no guarantee that bottled water has lower concentrations of this contaminant. If you drink bottled water, choose brands that provide water quality information indicating their water has levels of chromium-6 below 0.06 ppb or that use reverse osmosis filtration to treat their water.
Because infants can be especially sensitive to carcinogenic chemicals, it is particularly important to use safer water when preparing infant formula. Water treated with a reverse osmosis filter will contain fewer contaminants and be safer for babies than bottled water.
6. Can I test my own tap water for chromium-6?
Most commercial water quality laboratories do not offer this test.
7. Besides drinking water, how else can I be exposed?
Other sources of exposure to hexavalent chromium include contaminated food and contaminated workplace air, especially for those working in metallurgy or leather-tanning facilities. Contaminated soil particles may also be a source of exposure via ingestion or inhalation. Widespread industrial use has led to detections of chromium-6 in two-thirds of current or former Superfund sites.
8. Are some people more vulnerable to the effects?
Yes. Fetuses, infants, and children have a higher sensitivity to carcinogenic chemicals. Their developing organ systems are more susceptible to damage from chemical exposures, and less able to detoxify and excrete chemicals.
In addition, people with less acidic stomachs appear to have a limited ability to convert chromium-6 to chromium-3, exposing them to higher levels of the toxic form and putting them at greater risk. Using common antacids and proton pump inhibitors can reduce stomach acidity. Other conditions that can inhibit stomach acid production include infection with Helicobacter pylori (a common bacterium linked to ulcers), pernicious anemia, pancreatic tumors, mucolipidosis type IV and some autoimmune diseases.
9. What other chemicals in my tap water should I be concerned about?
Check out EWG's tap water database for an in-depth look at water contaminants, including drinking water quality information for 48,000 communities in 45 states and the District of Columbia.
10. What is EPA doing to promote safe drinking water?
Not enough. In the case of hexavalent chromium, the EPA has taken no specific action to limit amounts in drinking water. The agency has left in place an inadequate standard for total chromium, set nearly 20 years ago. It does not distinguish between toxic hexavalent and nutritionally essential trivalent chromium and cites "allergic dermatitis" as the only health concern. The agency has not set a new, enforceable drinking water standard for any contaminant since 2001.
Recently, however, the federal government has begun to focus a critical eye on chromium-6 and other water contaminants. EWG recommends that the EPA set a legal limit for hexavalent chromium in drinking water as quickly as possible and require water utility testing to assess exposures nationwide.
11. Is bottled water a safe alternative?
Drinking bottled water might seem like a good way to avoid exposing yourself to hexavalent chromium, but there is no guarantee that bottled water contains less of this contaminant. Furthermore, there is no legal limit for chromium-6 in bottled water, so consumers cannot assume it is free of it. EWG has assessed bottled water quality and the industry's labeling practices and isn't impressed with either. If you drink bottled water, choose brands that provide water quality information indicating that the water has less than 0.06 ppb of chromium-6 or that use reverse osmosis filtration to purify it. Overall, test results strongly indicate that the purity of bottled water cannot be trusted. As EWG's Jane Houlihan says,
"It's buyer beware with bottle water. The bottled water industry promotes its products as pure and healthy, but our tests show that pollutants in some popular brands match the levels found in some of the nation's most polluted big city tap water systems. Consumers can't trust that what's in the bottle is anything more than processed, pricey tap water."
Plus, there's all that plastic waste.