Applied occupational and environmental hygiene最新文献

Hexavalent chromium [Cr(VI)] is recognized as an inhalation carcinogen, based primarily on the increased incidence of lung cancer among occupationally exposed workers. To assess the carcinogenic potency of Cr(VI), both the U.S. Environmental Protection Agency and the Occupational Safety and Health Administration have relied on data from a 1930s cohort of workers from the Painesville, Ohio, chromate production plant. However, the exposure information for this cohort has several shortcomings. In an effort to provide better exposure information, we present here recently identified historical exposure data for the Painesville workers. More than 800 measurements of airborne Cr(VI) from 23 newly identified surveys conducted from 1943 to 1971 are presented. The results indicate that the highest Cr(VI) concentrations recorded at the plant occurred in shipping (e.g., bagging of dichromate), lime and ash, and filtering operations, with maximum yearly average Cr(VI) concentrations of 8.9, 2.7, and 2.3 mg/m(3), respectively. The locker rooms, laboratory, maintenance shop, and outdoor raw liquor storage areas had the lowest average Cr(VI) air concentrations over time, with yearly average concentrations that rarely exceeded the historical and current Threshold Limit Value TLV(R) of 0.05 mgCr(VI)/m(3) (0.1 mgCrO(3)/m(3)). Concentrations generally decreased in the plant over time. The average airborne concentration of Cr(VI) in the indoor operating areas of the plant in the 1940s was 0.72 mg/m(3), that from 1957 through 1964 was 0.27 mg/m(3), and that from 1965 through 1972 was 0.039 mg/m(3). Although in some ways limited, these data are of sufficient quality to allow for exposure reconstruction for workers employed at this plant from 1940 to 1972, and to provide the basis for an improved cancer risk assessment.

A prototype sampling system for measuring respirator workplace protection factors (WPFs) was developed. Methods for measuring the concentration of contaminants inside respirators have previously been described; however, these studies have typically involved continuous sampling of aerosols. Our work focuses on developing an intermittent sampling system designed to measure the concentration of gases and vapors during inspiration. This approach addresses two potential problems associated with continuous sampling: biased results due to lower contaminant concentrations and high humidity in exhaled air. The system consists of a pressure transducer circuit designed to activate a pair of personal sampling pumps during inspiration based on differential pressure inside the respirator. One pump draws air from inside the respirator while the second samples the ambient air. Solid granular adsorbent tubes are used to trap the contaminants, making the approach applicable to a large number of gases and vapors. Laboratory testing was performed using a respirator mounted on a headform connected to a breathing machine producing a sinusoidal flow pattern with an average flow rate of 20 L/min and a period of 3 seconds. The sampling system was adjusted to activate the pumps when the pressure inside the respirator was less than -0.1 inch H(2)O. Quantitative fit-tests using human subjects were conducted to evaluate the effect of the sampling system on respirator performance. A total of 299 fit-tests were completed for two different types of respirators (half- and full-facepiece) from two different manufacturers (MSA and North). Statistical tests showed no significant differences between mean fit factors for respirators equipped with the sampling system versus unmodified respirators. Field testing of the prototype sampling system was performed in livestock production facilities and estimates of WPFs for ammonia were obtained. Results demonstrate the feasibility of this approach and will be used in developing improved instrumentation for measuring WPFs.

Pneumatic nail guns greatly increase worker productivity and are extensively used in wood frame building construction, with especially high use in residential construction. One surveillance report of nail gun injuries in Washington State has been published; however, other literature consists largely of case reports and case series in trauma journals. The major objective of the current study was to investigate the occurrence of nail gun-associated injuries among construction workers and to identify preventable work-related factors associated with these injuries. Nail gun-related injuries occurring among a cohort of 13,347 carpenters in Ohio who worked union hours during the time period January 1, 1994, until September 30, 1997, were identified by matching the cohort with workers' compensation claims made to the Ohio Bureau of Workers' Compensation. We also analyzed workers' compensation claims for North Carolina Home Builders Association members for the period July 1996-November 1999 to identify nail gun-related injuries. Analyses included stratified analyses of claims by nature and body part injured, calculation of nail gun injury rates, and analyses of free text descriptions of injuries. Overall, nail gun injuries were responsible for 3.9 percent of workers' compensation claims with 8.3 percent to 25.5 percent of claims involving paid lost work time. The overall rate of nail gun injuries (cases per 200,000 work hours) was 0.33 in North Carolina and 0.26 in Ohio, reflecting the greater concentration of wood frame construction workers in the North Carolina population studied. Higher rates of injury were observed for carpenters in North Carolina and among residential carpenters in Ohio. The predominant body part injured was the hands/fingers, with 80 to 89 percent of injuries being nail punctures. Analyses of free text information for puncture injuries found approximately 70 percent of injuries to occur during the framing/sheathing stage of construction. Our data suggest that approximately 69 percent of puncture injuries may be due to an inadvertent gun discharge or misfire, preventable in large part by the use of sequential triggers. Worker training and education also are important components of nail gun injury prevention.

Polymeric diphenylmethane di-isocyanate (PMDI) is a precursor or an intermediate in the manufacture of pure MDI and is used in many industrial applications. Potential health effects of diisocyanates are generally considered to include irritation and respiratory sensitization, dictating the need for low occupational hygiene standards and robust hygiene monitoring methods. A wide range of methods has been developed or adopted for this purpose but questions concerning their ability to accurately sample MDI aerosols in the occupational environment have often been raised. In order to provide such information, studies have been conducted to compare several MDI sampling systems: the Institute of Occupational Medicine (IOM) 25-mm open-faced inhalable dust sampler; the 13-mm Millipore Swinnex Cassette sampler; the 37-mm open-face Millipore cassette; the midget-impinger, the glass tube containing glass wool, and two direct reading paper tape monitors. The program was comprised of two phases, the first being a preliminary comparison of the collection efficiencies of the IOM, 13 mm and midget-impinger at a range of orientations to air flow, aerosol particle sizes, and sampling flow rates, using inert polyethylene glycol aerosols. The second phase compared all samplers operating according to each manufacturer's recommendations and sampling PMDI aerosols at a range of particle sizes and concentrations. All studies were conducted in a wind tunnel. All filter methods performed well in atmospheres containing small particles except impingers that required a filter backup. In general, the variability of all the samplers was high for larger particle size ranges. Direct reading monitors showed low efficiencies.

In 2000, the American Conference of Governmental Industrial Hygienists (ACGIH(R)) changed its 1971 threshold limit value (TLV) for 8-hour time-weighted average (TWA) exposure to asphalt from 5 mg/m(3) total particulate (generally < or =40 micrometer [microm] diameter) to 0.5 mg/m(3) inhalable particulate (< or =100 microm aerodynamic diameter) as benzene-soluble aerosol. To date, no inhalable particulate sampling method has been standardized and validated for asphalt fume. Furthermore, much of the historical data were collected using total particulate samplers, and the comparability of total versus inhalable size fractions of asphalt fume is not known. Therefore, the present study compared results from two types of asphalt fume samplers: 1) a traditional total particulate sampler with a 37-mm filter in a closed-face cassette with a 4-mm orifice (NIOSH 5042) versus (2) an inhalable particulate sampler designed by the IOM with a 15-mm orifice. A total of 75 simultaneous pairs of samples were collected, including personal and area samples from 19 roofing and asphalt production facilities operated by 7 different manufacturers. Each sample was analyzed for total mass collected and for benzene-soluble mass. Data from the two sampling methods (total versus inhalable) were comparable for asphalt fumes up to an aerosol concentration of 10 mg/m(3). However, we conclude that the traditional total particulate method is preferable, for this reason: The vast majority of asphalt fume particles are <12.5 microm in diameter. The traditional sampler is designed to collect primarily particles < or =40 microm, while the IOM sampler is optimized for collecting particles < or =100 microm. Thus, the traditional sampler is less likely than the IOM sampler to collect the larger-size fraction of airborne particles, most of which are non-asphalt dust.