Michael G. Gressel

Advantages of Real-Time Data Acquisition for Exposure Assessment

Abstract A computerized data acquisition system, utilizing real-time instrumentation and a video taping system, can provide the information necessary to identify the sources or activities which most affect worker exposure levels. Integrated workplace samplers, such as pumps with filters or charcoal tubes, may indicate a certain level of exposure. However, due to the complexity of the process or work cycle, an evaluation of activities affecting exposure patterns may be difficult. Such a system, utilizing a computer, real-time instrumentation, and video taping, has been used successfully in three different NIOSH studies. In the first, a study of manual weigh-out and transfer of powders, the data acquisition system identified the scooping operation as the component of the work cycle which most affected the worker dust exposures. Because of the short work cycle, typically 30 seconds or less, filter sampling could not isolate this work element as the major cause of worker dust exposure. In the second study, an...

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.

Video Exposure Monitoring—A Means of Studying Sources of Occupational Air Contaminant Exposure, Part I—Video Exposure Monitoring Techniques

Abstract Conventional sampling with pumps and sampling media can be used to determine whether exposures to air contaminants are excessive. Unfortunately, such results provide few insights into the reasons for the excessive exposures. However, Video Exposure Monitoring can be used to identify the sources causing these excessive exposures. Any movable instrument that has an analog or digital output can potentially be used for Video Exposure Monitoring. The instrument should be light enough to mount on a worker, be specific for the chemical interest, and have a short time constant. Although most existing direct-reading instruments do not simultaneously meet all these requirements, currently available instruments, such as aerosol photometers, photoionization detectors, and portable infrared analyzers have been used effectively. The analog or digital output from direct-reading instruments can be recorded by data-logging devices. The data-logging devices transfer the exposure data to a personal computer for sto...

Acquisition and Spreadsheet Analysis of Real Time Dust Exposure Data: A Case Study

Abstract Personal sampling with a light-scattering monitor connected to a data logger has been used to evaluate the effectiveness of a high-velocity, low-volume (HVLV) sander hood used in a plant manufacturing reinforced plastics. Exposures to sanding dust were determined for two workers, one using a sander with a hood, the other using a sander with none. Both workers were partners in a two-person team sanding a truck hood and fender assembly. Side-by-side filter sampling was conducted to calibrate the aerosol monitor. Data logger output for each worker was combined into a single spreadsheet program. Simultaneous video recording allowed worker activity variables (sanding, compressed air blowing, and other) to be coded onto the spreadsheet, which permitted calculation of the contribution of each activity to each workers dose of dust. The computerized data acquisition system permitted identifying activities that change worker exposures through review of the work cycle while tracking worker exposures. Thoug...

Video Exposure Monitoring—A Means of Studying Sources of Occupational Air Contaminant Exposure, Part 2—Data Interpretation

Abstract Excessive exposures to air contaminants can be determined by conventional sampling with pumps and sampling media; however, such results do not provide insights into the reasons for the excessive exposures. The analog or digital output from direct-reading instruments can be captured by using data-logging equipment. While data are being logged from direct-reading instruments, the activities in the workplace can be recorded using a video camera. These data can be analyzed to find reasons for excessive air contaminant exposures. Three approaches have been used to quantitatively present the results of real-time sampling. First is the use of descriptive statistics to describe the data. Frequently, useful insights can be obtained from descriptive statistics and graphs. When activities in question are sufficiently separated in time, this can be a very fruitful approach. At other times, a second approach, statistical analysis, may be needed to evaluate whether a certain activity is causing an increase in ...

Effective Local Exhaust Ventilation for Controlling Formaldehyde Exposures during Embalming

Abstract Previous studies have found that formaldehyde exposures to embalmers during the embalming process exceeded current occupational health criteria and standards. There are currently just over 20,000 mortuaries in the United States, employing 75,000 people. Mortuaries, as small businesses, typically do not have access to the occupational health and safety expertise that larger companies do. Therefore, a research study was conducted to develop and evaluate a local exhaust ventilation system to control formaldehyde exposures. The control design that was developed consisted of a pair of 6-ft-long slot hoods placed on each side of the embalming table. Through a series of laboratory tests, an optimum flow rate (20 m3/min) was determined for the local exhaust ventilation system. The final design was field tested at a college of mortuary science to determine its effectiveness. A series of 16 tests were conducted with a variety of different embalming procedures. For each test, two personal and three area sam...

Short-Term Monitoring of Formaldehyde: Comparison of Two Direct-Reading Instruments to a Laboratory-Based Method

Airborne formaldehyde concentrations can be measured using several different techniques, including laboratory-based methods and direct-reading instruments. Two commercially available direct-reading instruments, an RKI Instruments Model FP-30 and a PPM Technology Formaldemeter htV, were compared with National Institute for Occupational Safety and Health Method 2016 in different test environments to determine if these direct-reading instruments can provide comparable results. The methods yielded the following mean concentrations for 47 samples: NIOSH Method 2016, 0.37 ppm; FP-30, 0.29 ppm; and htV, 0.34 ppm. Results from both of the direct-reading instruments were correlated with the laboratory-based method (R2 = 0.78 for FP-30, and 0.902 for htV). Comparison of the means of the three methods showed that on average the FP-30 instrument (p < 0.001) differed statistically from NIOSH Method 2016, whereas the htV (p = 0.15) was not statistically different from the NIOSH method. Sensitivity and specificity tests demonstrated that the FP-30 had sensitivity above 60% to detect formaldehyde concentrations at all the cutoff levels tested, whereas the htV appeared to have greater sensitivity above 88% for the levels evaluated.

Workstation Design Improvements for the Reduction of Dust Exposures During Weighing of Chemical Powders

Abstract Ventilated booth workstations often do not provide complete dust control during the manual transfer and weigh out of chemical powders. In a typical process, a worker removes powder from the bulk material drum with a scoop, weighs the powder into a paper bag, and then places the full bag into a second drum. A previous study identified points of exposure in a ventilated weigh-out operation at a plastics manufacturing plant. Eddies in front of the worker and inside the weigh-out drum hindered dust control. The depth of the powder in the weigh-out drum also contributed to increased exposures. This follow-up study sought to apply and evaluate three different control modifications of the weigh-out station. The first control was the modification of the worktable to streamline the process. The second control was a local exhaust hood placed at the lip of the bulk material drum. This hood controlled the eddy in the bulk material drum. The last control was an air shower, i.e., a low-velocity, fresh air supp...

SILICA EXPOSURE IN HAND GRINDING STEEL CASTINGS

Exposure to silica dust was studied in the grinding of castings in a steel foundry that used conventional personal sampling methods and new real-time sampling techniques developed for the identification of high-exposure tasks and tools. Approximately one-third of the personal samples exceeded the National Institute for Occupational Safety and Health recommended exposure limit for crystalline silica, a fraction similar to that identified in other studies of casting cleaning. Of five tools used to clean the castings, the tools with the largest wheels, a 6-in. grinder and a 4-in. cutoff wheel, were shown to be the major sources of dust exposure. Existing dust control consisted of the use of downdraft grinding benches. The size of the casting precluded working at a distance close enough to the grates of the downdraft benches for efficient capture of the grinding dust. In addition, measurements of air recirculated from the downdraft benches indicated that less than one-half of the respirable particles were removed from the contaminated airstream. Previous studies have shown that silica exposures in the cleaning of castings can be reduced or eliminated through the use of mold coatings, which minimize sand burn-in on the casting surface; by application of high-velocity, low-volume exhaust hoods; and by the use of a nonsilica molding aggregate such as olivine. This study concluded that all these methods would be appropriate control options.

The development and testing of a prototype mini-baghouse to control the release of respirable crystalline silica from sand movers.

ABSTRACT Inhalation of respirable crystalline silica (RCS) is a significant risk to worker health during well completions operations (which include hydraulic fracturing) at conventional and unconventional oil and gas extraction sites. RCS is generated by pneumatic transfer of quartz-containing sand during hydraulic fracturing operations. National Institute for Occupational Safety and Health (NIOSH) researchers identified concentrations of RCS at hydraulic fracturing sites that exceed 10 times the Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) and up to 50 times the NIOSH Recommended Exposure Limit (REL). NIOSH research identified at least seven point sources of dust release at contemporary oil and gas extraction sites where RCS aerosols were generated.  NIOSH researchers recommend the use of engineering controls wherever they can be implemented to limit the RCS released. A control developed to address one of the largest sources of RCS aerosol generation is the NIOSH mini-baghouse assembly, mounted on the thief hatches on top of the sand mover. This article details the results of a trial of the NIOSH mini-baghouse at a sand mine in Arkansas from November 18–21, 2013.  During the trial, area air samples were collected at 12 locations on and around a sand mover with and without the mini-baghouse control installed. Analytical results for respirable dust and RCS indicate the use of the mini-baghouse effectively reduced both respirable dust and RCS downwind of the thief hatches. Reduction of airborne respirable dust ranged from 85–98%; reductions in airborne RCS ranged from 79–99%. A bulk sample of dust collected by the baghouse assembly showed the likely presence of freshly fractured quartz, a particularly hazardous form of RCS.  Planned future design enhancements will increase the performance and durability of the mini-baghouse, including an improved bag clamp mechanism and upgraded filter fabric with a modified air-to-cloth ratio. Future trials are planned to determine additional respirable dust and RCS concentration reductions achieved through these design changes.