Is Hexavalent Chromium (Hex Chrome; Chrome VI) A Carcinogen?

Written by Henry P. Shotwell, Ph.D., CIH, Vice-President

In 1990, the International Agency for Research on Cancer (IARC), an agency of the World Health Organization (WHO), published their findings on chromium and chromium compounds as carcinogens. Chromium may be isolated in any of three volume states: Chrome 0 or metallic chromium; Chrome III called “Chrome 3” or Chrome VI called “Chrome 6,” also called hexavalent chromium. Neither Chrome 0 nor Chrome III has shown the ability to cause cancer. Chrome VI, on the other hand, is a well-known lung carcinogen. (DeFlora, S., “Threshold Mechanisms and Site-Specialty in Chromium (VI) Carcinogens,” Carcinogens, Volume 21, No. 4, pages 533-541, April, 2000, Oxford University Press.) However, according to DeSilva, development of lung cancer “…requires massive exposures, as is only encountered in well-defined occupational settings…”

Neither the chromium found in metal plating (like chrome trim on a can) nor the chrome found in medicines like chromium picolinate is in the hexavalent form and is not carcinogenic. The chrome found in the fumes formed by welding stainless steel and released into a welder’s breathing zone is in the hexavalent state and can cause lung cancer if the welder breathes in a high enough dose of Chrome VI often enough. The Occupational Safety and Health Administration (OSHA) has determined that a continuous, 8-hour exposure to hexavalent chromium of 0.005 milligrams per cubic meter of air, or less, is an acceptable exposure level (OSHA Regulation 29 CFR 1910.1026).

While this exposure level may be legally acceptable, any means of further reducing exposure to hexavalent chromium that is available should be used. The principal method is by introducing engineering controls, including Local Exhaust Ventilation and the use of respirators.

Portable welding fume extractors work well when placed close enough to the point of operation to capture the “smoke” created by welding, thereby reducing or eliminating the smoke from entering the welder’s breathing zone. Using a respirator to filter out the smoke particles is the last line of defense. A respirator has to be correctly chosen for the anticipated contaminant, but it also has to be correctly fitted to the worker’s face, and tested to be sure there is no leakage around the edges of the respirator that might allow contaminants to bypass the filter system.

Common activities where hexavalent chromium exists are in welding of stainless steel or chrome plated metals, electroplating of chrome, printing or painting operations where chromium inks or paints are used.

In each of these cases, these activities should be sampled to determine if the exposure levels are safe. If it is a work situation, then compliance with the OSHA Standard for hexavalent chromium (29 CFR 1910.1026) must be addressed.