Chromium-6:
Health and Life-Cycle Hazards

Hexavalent chromium, or chromium-6 (CrVI), hit the news recently when a study found the chemical in the tap water of several major U.S. cities. A groundwater pollutant notorious from the 2000 hit movie “Erin Brockovich,” the chemical in vapor form is also a regulated occupational hazard. Should we be taking a more critical look at chrome plating and stainless steel?

Not all chromium is created equal. In its more stable trivalent form (CrIII), the metal does not normally endanger human health. And after unstable CrVI enters the body, it quickly reduces to CrIII. But cell damage occurs in the process, and CrVI is a known carcinogen when inhaled as well as a possible carcinogen when ingested. A variety of protective coatings, dyes, and pigments used for cars and boats as well as leather-tanning chemicals contain the metal. But aside from chrome-plated products, including solar collectors coated with high-efficiency “black chrome,” the manufacture of most building materials does not directly involve CrVI. The chromium that makes stainless steel “stainless” is the relatively benign non-valent chromium (Cr0), although welding stainless steel can generate CrVI fumes. Metal building products manufactured with CrVI do not generally present a health hazard once in use.

CrVI does leach out of pressure-treated wood containing chromated copper arsenate (CCA), and although CCA-treated wood was eliminated from most residential products, including decking, in the early 2000s, it is still widely used in commercial applications. Because of the rapid reduction to CrIII in soil, most studies suggest that CCA-treated wood does not cause widespread
pollution while in use. However, CrVI is one of the many toxic substances that make CCA-treated wood a health and environmental hazard when it is used near water, burned, or piled in landfills.

When we consider the entire life cycle of products using chrome, additional problems crop up. Chromite mining pollutes groundwater with CrVI, which means that stainless steel manufacture—by far the largest application for chromium—creates a major health hazard long before the steel is made into door hardware, commercial sinks, and high-end kitchen appliances.

The waste-disposal end of the life cycle is also implicated in problems. According to the U.S. Environmental Protection Agency (EPA), people who live near factories that use chromium are more likely to have CrVI in their drinking water. While EPA does not currently list CrVI as an oral carcinogen, the federal Agency for Toxic Substances and Disease Registry reports an increase in stomach tumors from CrVI-contaminated water. Industry, including chrome-plating, is the primary source.

The durability and attractiveness of stainless steel and chrome-based coatings make these materials popular. But it may be time to start questioning their ubiquity and using recycled-content materials whenever possible.

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IMAGE CREDITS:
1. Illustration: Peter Harris

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