Hexavalent chromium exposures and exposure-control technologies in American enterprise: results of a NIOSH field research study.

The National Institute for Occupational Safety and Health (NIOSH) conducted 21 field surveys in selected industries to characterize workers' exposures to hexavalent chromium-containing airborne particulate and to evaluate existing technologies for controlling these exposures. Hexavalent chromium Cr(VI) is a respiratory irritant and chronic inhalation may cause lung cancer. Primary evaluation methods included collection of full work shift, personal breathing-zone (PBZ) air samples for Cr(VI), measurement of ventilation system parameters, and documentation of processes and work practices. This study emphasized evaluation of engineering exposure control measures, so PBZ exposures were measured on the outside of personal protective equipment, for example, respirators. Field surveys were conducted in two chromium electroplating facilities, including one where full-shift PBZ exposures to Cr(VI) ranged from 3.0 to 16 times the 1 micro g/m(3)NIOSH recommended exposure limit (REL) despite several engineering controls on the plating tanks. At a painting and coating facility that used Cr(VI)-containing products, full-shift exposures of painters and helpers (2.4 to 55 micro g/m(3)) exceeded the REL, but LEV effectiveness was limited. Other operations evaluated included welding in construction; metal cutting operations on chromium-containing materials in ship breaking; chromate-paint removal with abrasive blasting; atomized alloy-spray coating; foundry operations; printing; and the manufacture of refractory brick, colored glass, prefabricated concrete products, and treated wood products. NIOSH researchers concluded that, in many of the evaluated processes, Cr(VI) 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 to this range. Most operations judged to be moderately difficult to control to this range involve joining and cutting metals with relatively high chromium content. Nonetheless, exposures in a wide variety of other processes were judged more easily controllable to the current REL or below, or were found to be minimal, including some operations meeting the general descriptions named above but with different specific operating parameters producing lower Cr(VI) exposures.

A long-term study of the development of N2O controls at a pediatric dental facility.

A review is given of National Institute for Occupational Safety and Health (NIOSH) efforts to control N2O at a pediatric dental operatory from 1978 to the present. Measurements of N2O concentrations were made on four occasions before and after installation of different controls, using an infrared analyzer. Air velocity and volumetric flow measurements also were taken, Video imaging was done in some cases simultaneously with real-time N2O measurements to correlate work practices with exposure data. An infrared imaging system was used to identify sources of N2O. Critical components of resulting recommendations for control include monitoring of N2O concentrations; use of engineering controls, such as a scavenging mask, an effective dilution ventilation system, and auxiliary exhaust; good work practices; maintenance of the equipment; and worker education. Data presented strongly supports the hypothesis that better implementation of controls leads to reduction of N2O exposures. N2O concentrations were reduced by a factor of 61 from their initial levels. The current NIOSH recommended exposure limit of 25 ppm TWA during the time of N2O administration appears to be achievable.

The control of press cleaning solvent vapors in a small lithographic printing establishment.

Small businesses frequently have inadequate in-house expertise to solve a variety of safety and health problems. The National Institute for Occupational Safety and Health (NIOSH) has therefore conducted a demonstration project in the commercial lithographic printing industry, which consists largely of small companies, in an effort to establish suitable control technology for airborne solvent vapors released primarily during press cleaning operations. These solvent vapors have a number of potential adverse health effects, including narcosis, kidney and liver damage, and cancer. Also, airborne anti-offset powder is a potential allergic sensitizer and cause of occupational asthma. As a means of controlling worker exposures to the vapors and dust, a local exhaust inlet was attached to the side of the press adjacent to the paper delivery point. Tempered outside air was introduced through ceiling outlets installed to make up for the exhausted air. Measurements of press operator exposure and area concentrations of solvent vapors and area concentration of anti-offset powder were made before and after installation of the new ventilation controls. Vapor concentrations were reduced by 73 percent for the press operators. Area concentrations of the vapors were reduced by 86 percent and dust concentration by 67 percent. The ventilation system was found to be suitable for vapor and dust control, although substitution of a cleaning solution containing non-carcinogenic solvents for solutions containing carcinogens was recommended.

Nitrous oxide control in the dental operatory: auxiliary exhaust and mask leakage, design, and scavenging flow rate as factors.

Two new local exhaust systems, intended primarily to control patient mouth emissions of N2O, were installed in a dental operatory, and resulting exposure concentrations to dental personnel were observed. The exposures were found to be typically unaffected by the presence and operation of these new controls. Laboratory testing on a head form, in conjunction with the operatory observations, established that mask leakage due to poor fit was the primary cause of N2O emissions. An improved mask fit and the addition of a slotted skirt around the outer mask shell individually resulted in greatly reduced leakage rates in the laboratory tests. Also, exhaust systems placed on the chin, on the chest, or in the mouth proved effective in capturing mouth emissions simulated by a breathing machine and head form.