Hexavalent chromium exposure can result in long-lasting health effects from the inhalation of welding fumes. When welding, the application of heat creates fumes that without protection can easily be inhaled by an operator. Hexavalent chromium fumes are produced from the welding of stainless steel, chrome alloys, and chrome coated metals. Employers should take precautions to reduce employee exposure through the use of welding fume extractors to protect respiratory and overall long term employee health.
When heated, chromium-containing metal creates fumes that oxidize or form the valence state of hexavalent chromium (Cr(VI)). The amount of exposure to Cr(VI) depends on the amount of chromium in the metal as well as the type of welding process. In the steel industry, stainless steel and chromium alloys contain about 11.5 – 30% chromium by weight. Industrial processes widely utilize stainless steel due to its corrosion resistance and durability. Certain welding processes, such as shielded metal arc, have been shown in research studies to produce higher amounts of Cr(VI) fumes.
Hexavalent chromium is a toxic form of chromium that can lead to damaging health effects due to the high absorbability factor, unstable state, and carcinogenic properties. Once hexavalent chromium enters the body, it reduces to a more stable form creating free radicals that damage DNA, cells, and proteins. Free radicals in the body cause oxidation stress and possible DNA mutations leading to cancer.
The International Agency for Research on Cancer (IARC) identifies hexavalent chromium as carcinogenic to humans. Exposure to hexavalent chromium mainly causes lung cancer but can also generate growth of other types of cancer such as sinonasal, oral, and esophageal. Once hexavalent chromium penetrates the lungs, it can enter the bloodstream causing damage and other possible cancer risks to vital organs such as the liver. The cancer risk from occupational exposure to hexavalent chromium depends on the intensity of the exposure, duration, and personal health of the welder. Full-time or project welders exhibit higher risks of developing cancer than part-time workers. Welders with asthma showed a slightly elevated cancer risk when compared to healthy workers.
Other than cancer, exposure to hexavalent chromium creates irritation in the nose and throat, and nose bleeds. Sinus and nasal symptoms need to be monitored to prevent the development of cancer. People exposed to hexavalent chromium can gain an allergy or sensitivity leading to wheezing, shortness of breath, bronchitis, and asthma. Also, exposure to hexavalent chromium can damage the skin, eyes, kidney, and liver as well as provoke pulmonary congestion, abdominal pain, and teeth yellowing and irritation.
OSHA enforces strict regulations regarding worker exposure to hexavalent chromium in several industries; and, subsequently established stringent regulations for workers who are potentially exposed to it in the general, construction, shipyard, and marine terminal industries. In addition, OSHA requires employers to protect employees’ health from inhalation or direct contact with hexavalent chromium fumes, as lifelong health effects can result from unprotected overexposure to hexavalent chromium fumes.
According to OSHA, common processes that can lead to the inhalation of airborne Hexavalent Chromium (dust, fume, or mist) include:
All employers whose employees could potentially be exposed to hexavalent chromium should conduct sampling to determine the level of exposure. The Permissible Exposure Limit (PEL) for hexavalent chromium is 5 micrograms per cubic meter of air (5µg/m3). The “Action Level” is 2.5µg/m3 (calculated as an 8-hour TWA). Employers legally must implement engineering or work practice controls if air samples meet or exceed the action level to ensure exposure does not exceed the PEL.
Recommended Engineering Control Measures for reducing exposure to CR(VI) that exceeds the PEL include*: