Engineering Controls Database

Control of Hexavalent Chromium Exposures

Problem:	Hexavalent chromium (Cr(VI)) compounds are a group of chemical substances that contain the metallic element chromium in its positive-6 valence (hexavalent) state. Occupational exposures to Cr(VI) occur during the production of stainless steel, chromate chemicals, and chromate pigments. Cr(VI) exposures also occur during other work activities such as stainless steel welding, thermal cutting, chrome plating.
What this means to you:	NIOSH considers all Cr(VI) compounds to be potential occupational carcinogens. An increased risk of lung cancer has been demonstrated in workers exposed to Cr(VI) compounds. Other adverse health effects associated with Cr(VI) exposure include dermal irritation, skin 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 the teeth. Cr(VI) compounds vary in solubility from those that are readily soluble to those which are practically insoluble in water. In 1975 NIOSH documented the carcinogenic effects of water-insoluble Cr(VI) compounds. The NIOSH 1988 testimony to OSHA on the air contaminants standard recommended that all Cr(VI) compounds, regardless of their degree of solubility in water, be considered occupational carcinogens. Description of NIOSH study: NIOSH conducted a study to quantitatively characterize occupational exposures to hexavalent chromium and to document engineering and other exposure-control measures and work practices affecting those exposures. The study was done under an inter-agency agreement with the Office of Regulatory Analysis (ORA) of the Occupational Safety and Health Administration (OSHA), U.S. Department of Labor. Twenty-one field surveys were conducted in selected industries to characterize workers’ exposures to hexavalent chromium airborne particulate and evaluate existing technologies for controlling these exposures. The facilities evaluated included: • chromium electroplating (2 facilities) • welding in construction • painting and coating • welding in construction • metal cutting procedures in ship breaking • chromate-paint removal with abrasive blasting • atomized alloy-spray coating • foundry operations • printing • manufacture of: refractory brick, colored glass, prefabricated concrete products, and treated wood products
Description of control:	Recommendations for reducing workers’ exposures to hexavalent chromium were made in each of the 21 field study reports. Detailed descriptions of these controls can be found in the reports. In some of the industrial sectors and operations studied, no unique or specialized engineering measures for hexavalent chromium exposure control were observed. Instead, many of the observed processes and equipment applications were typical of those common throughout industry such as used with dip tanks and grinding, sanding, and welding operations. The control of exposures in these operations is often best achieved with common exhaust ventilation approaches such as described in the ACGIH industrial ventilation manual. However, more specialized engineering measures for exposure control were observed and/or recommended during the field studies in some sectors and operations. For example: Chromium Electroplating: A combination of engineering measures may be needed to effectively control potential exposures from hard chrome plating tanks. At one facility, push-pull ventilation systems, polyethylene tarpaulins, and a foam-blanket mist-suppressant product were used. Push-pull ventilation was generally effective in moving air away from workers breathing zones but maintenance problems were found. In contrast to hard chrome plating tanks, bright chrome plating tanks presented less of a problem for controlling emissions. A wetting agent used as a surface-tension-reducing fume suppressant provided very effective control of emissions (244-9052-c). Spray Application of Chromate-Containing Paints: At one facility, it was found that the most effective measure for reducing emissions was the substation of paints with lower chrome content whenever possible. In addition, partially enclosed paint booths for large-part painting may not provide adequate containment capture (244-9053-c). Removal of Chromate Containing Paints: Abrasive blasting was used to remove existing chromate-containing paint prior to repainting a bridge. An enclosure of plastic sheeting was constructed to contain the spent abrasive and paint residue. No mechanical ventilation was provided to the containment structure. It was recommended that the containment structure be equipped with general-dilution exhaust ventilation that dischargers the exhausted air through a high-efficiency particulate air filtration system (244-9068-c). Operations Creating Concrete Dust: Portland cement naturally contains hexavalent chromium. In two such operations where concrete dust may be generated and inhaled by workers, water- spray systems were used to suppress dust during cleanup. The use of the water-spray systems resulted in visibly lower dust concentrations. All hexavalent chromium exposures at these facilities were low (244-9061-c, 244-9063-c).
Engineering and Physical Hazard Report Numbers:	244-03; 244-05-A-1; 244-05-A-2; 244-05-B; 244-05-C; 244-05-D; 244-05-E; 244-05-F; 244-05-G; 244-05-H; 244-07; 244-08; 244-1-00; 244-9052-A; 244-9052-B; 244-9052-C; 244-9053-B; 244-9053-C; 244-9054-A; 244-9054-B; 244-9054-C; 244-9055-B; 244-9055-C; 244-9056-B; 244-9056-C; 244-9057-B; 244-9057-C; 244-9058-B; 244-9058-C; 244-9059-B; 244-9059-C; 244-9060-B; 244-9060-C; 244-9061-B; 244-9061-C; 244-9062-B; 244-9062-C; 244-9063-B; 244-9063-C; 244-9064-B; 244-9064-C; 244-9065-B; 244-9065-C; 244-9066-B; 244-9066-C; 244-9067-B; 244-9067-C; 244-9068-B; 244-9068-C; 244-9069-B; 244-9069-C; 244-9070-B; 244-9070-C; 244-9071-B; 244-9071-C; 244-9594-B; 244-9594-C;
References:	Blade LM, Yencken S, Wallace ME, Catalano JD, Khan A, Topmiller JL, Shulman SA, Martinez A, Crouch KG, Bennett JS: Hexavalent chromium exposures and exposure-control technologies in American enterprise: results of a NIOSH field research study. J Occup Environ Hyg 4:596-618 (2007).
Keywords:	and chromate pigments chromate chemicals chrome chrome plating chromium production of stainless steel stainless steel welding thermal cutting
How well does this control work?	In many of the evaluated processes hexavalent chromium exposures at or below the current NIOSH REL are achievable. However, for some processes, it is unclear whether controlling exposures to this range is consistently achievable without respirator use. Some operations involving the application of coatings and finishes may be among those most difficult to control in this range. Most operations judged to be moderately difficult to control to this range involve joining and cutting metals with relatively high chromium content. Exposures in a wide variety of other processes were judged to be more easily controlled to the current REL or below.