Applied occupational and environmental hygiene最新文献

Particle boards and other wood boards are usually made with formaldehyde-based resins. Woodworkers are thus exposed to formaldehyde in vapor form as well as from airborne dust once it enters their respiratory tract. These workers remain exposed to formaldehyde released from the dust still present in their upper respiratory tract, even after their work shift. In assessing the risk associated with formaldehyde exposure, one needs to consider the relative importance of these two sources of exposure. This study proposes two kinetic models to estimate and compare the exposures. For various exposure scenarios, one model predicts the amount of formaldehyde absorbed from the ambient vapor form and the other predicts the amount absorbed by the respiratory tract upon its release from wood product dust. Model parameters are determined using data from published studies. Based on a daily work shift of 8 hr, with a dust concentration in air of 5 mg/m(3) and a formaldehyde concentration bound to dust of 9 microg/mg, model simulations predict that the amount of absorbed formaldehyde released from wood dust is approximately 1/100 of the amount absorbed from the ambient vapor form at a concentration level of 0.38 mg/m(3) (0.3 ppm). Since the formaldehyde concentration in wood dust used above is much higher than usually observed while the dust and vapor form formaldehyde concentrations are of the order of acceptable upper values, these results indicate that the formaldehyde exposure from wood dust is comparatively negligible.

Diffusive sampling combined with thermal desorption (DSTD) is considered useful in monitoring workers' exposures to organic vapors, not only due to its simplicity of operation in the field but, also, its simplifying the sample treatment, eliminating the use of extracting solvent, and increasing analytical sensitivity. Herein, the feasibility of applying DSTD in field conditions was assessed through a comparison of the results with those from the well-accepted active/charcoal method. Side-by-side active and diffusive (tube-type, Tenax TA as the adsorbent) samples, both personal and area, were collected and analyzed for xylenes, ethyl acetate, styrene, and n-butyl acetate in four different industrial settings. Statistically significant correlations were found between the two methods in personal samples with the correlation coefficients of 0.92, 0.90, 0.83, 0.88, and 0.97 for m&p-xylenes, o-xylene, n-butyl acetate, styrene, and ethyl acetate, respectively. A paired t-test revealed significant difference between the two methods for n-butyl acetate and styrene. For area sampling, statistical differences (p < 0.05) were found between the two methods, except for xylenes. The DSTD method had, mostly, a lower concentration than the active method, with the bias ranging from 10.2 to -54.4 percent. The possible causes for the discrepancies are discussed. These results suggest that though DSTD protocols can be considered as a simple approach for screening workers' exposures to volatile organics, they should be applied with caution since diffusive sampling is potentially affected by various environmental conditions and adsorptive characteristics.

A negative pressure user seal check (NPUSC) method was evaluated for its ability to adequately detect known exhalation valve leakage into a respirator. Three valves with different types of damage were included. Twenty-six test subjects, wearing full facepiece respirators, were asked to perform a NPUSC. Their responses as to whether they passed or failed the user seal check were compared to fit testing results from two quantitative fit test methods: ambient aerosol and controlled negative pressure. In addition, equipment developed at the University of Cincinnati was used to measure in-mask pressures that are generated during the performance of NPUSCs. This technique was employed to assess the ability of respirator wearers to properly conduct user seal checks. The data were analyzed to determine if the user seal check procedure is an effective method for detecting known exhalation valve damage. All test subjects reported passing the user seal check with the undamaged valve. With the warped valve installed, 95 percent of test subjects reported passing the user seal check. With the slit valve installed, 73 percent of test subjects reported passing. With the dirty valve installed, 65 percent reported passing. All fit factors, measured with the damaged valves, were below the Occupational Safety and Health Administration-recognized pass/fail criteria except one fit test with the respirator equipped with the slit valve. Results from the in-mask pressure measurements confirmed whether or not the subject properly conducted a user seal check, but did not detect respirator leakage. In conclusion, the performance of a NPUSC rarely helped to identify damaged exhalation valves. These results support the need for respirator inspection prior to donning with periodic fit testing and the performance of user seal checks as necessary components of an adequate respiratory protection program.

Construction is one of the most hazardous industries in the United States. Occupational health research to characterize the hazards in construction work has been hampered by the lack of a systematic approach to classification of construction work and its associated hazards. A taxonomy of construction work, a nested system of classification, has been developed to systematize the collection and reporting of exposure assessment data for the characterization and reduction of hazards and the prevention of musculoskeletal injury. This taxonomy subdivides construction work into the categories of stage, operation, task, and activity. It is based on a bidding specification system already in use within the industry and thus provides a terminology common among workers, supervisors, and managers. The identification of tasks and activities that are present in multiple stages and/or trades contributes to the efficiency of exposure data collection and facilitates the generalizability to other settings for both exposure data and intervention evaluations. The taxonomy provides a framework and vocabulary that facilitates field work and participatory research activities. It can also potentially be linked to personnel and economic data for estimation of costs of safety and health problems, as well as benefits of interventions. Although developed for construction ergonomics, the taxonomic approach has application to non-routine work in other industry sectors and possibly in occupational health research other than ergonomics.

In this work the determination of the aspiration efficiency of personal aerosol samplers, commonly used in occupational exposure assessment, is investigated by means of CFD techniques. Specifically, it will be described a code to calculate the particle trajectories in a given flow field. At the present state the code considers only the effects of the mean flow field on the particle motion, whereas the turbulent diffusion effects are neglected. Comparisons with experimental measurements are also given in the framework of a research contract, supported by the European Community, with several experimental contributions from the participants. The main objective of the European research is to develop a new approach to experimentation with airborne particle flows, working on a reduced scale. This methodology has the advantage of allowing real-time aerosol determination and use of small wind tunnels, with a better experimental control. In this article we describe how the methodology has been verified using computational fluid dynamics. Experimental and numerical aspiration efficiencies have been compared and the influence of gravity and turbulence intensity in full and reduced scale has been investigated. The numerical techniques described here are in agreement with previous similar research and allow at least qualitative predictions of aspiration efficiency for real samplers, taking care of orientation from the incoming air flow. The major discrepancies among predicted and experimental results may be a consequence of bounce effects, which are very difficult to eliminate also by greasing the sampler surface.

There is little published information concerning the epidemiology of fatal injuries involving respiratory protection. We compiled a case series from U.S. Occupational Safety and Health Administration investigation reports from 1984 through 1995. For the 12-year period there were 41 incidents resulting in 45 deaths due to asphyxiation or chemical poisoning while wearing a respirator. There were 23 deaths related to airline respirators, 17 deaths involving use of negative pressure (air purifying) respirators, and 5 deaths involving self-contained breathing apparatus. Among the 23 deaths involving airline respirators, 15 were associated with compatible connection couplings for breathable air and inert gases. Three workers with beards died who wore tight-fitting respirators in an atmosphere that was immediately dangerous to life and health. Most of the fatalities involved regulatory and procedural violations, and would have been prevented by proper training and compliance with existing regulations. The information concerning the victims was limited but it did not appear that medical screening would have prevented any of the deaths.

This literature review summarizes engineering control technology research for dust and silica exposures associated with selected tasks in the construction industry. Exposure to crystalline silica can cause silicosis and lung fibrosis, and evidence now links it with lung cancer. Of over 30 references identified and reviewed, 16 were particularly significant in providing data and analyses capable of documenting the efficacy of various engineering controls. These reports include information on generation rates and worker exposures to silica and dust during four different tasks: cutting brick and concrete block, grinding mortar from between bricks, drilling, and grinding concrete surfaces. The major controls are wet methods and local exhaust ventilation. The studies suggest that while the methods provide substantial exposure reductions, they may not reduce levels below the current ACGIH threshold limit value (TLV) of 0.05 mg/m(3) for respirable quartz. Although further research on controls for these operations is indicated, it is clear that effective methods exist for significant exposure reduction.