M. Sheehan, West Chester University, West Chester, PA; J. Galloway, Cephalon, West Chester, PA; J. Zanini, Becton Dickinson, Juiz de Fora, Brazil; N. Orr, G. Barbi, Becton Dickinson, Franklin Lakes, NJ.
Mercury vapor area samples and mercury in urine samples were collected by plant personnel at a thermometer manufacturing plant to assess and reduce worker risk. This study investigates the effect of the implementation of a control strategy that was documented with mercury vapor area samples on mercury in urine values. Air samples were obtained using a Jerome 411 mercury vapor meter. During the time period a control implementation was effective, the relationship between the natural logarithm (ln) mercury vapor concentration vs. (month of the study) was determined using linear regression (r2 = 0.43, p<0.00001). Using the regression model, seven months after the control implementation, the plant mean (ln mercury vapor concentration) dropped to half its original value. Urine samples from plant personnel were taken quarterly and analyzed for elemental mercury. Ten workers with complete data sets for the time interval studied were included. The worker number, worker gender, plant area, mercury vs. nonmercury area, and the month of the study were used as independent variables in a multiple regression, with mercury in urine as the dependent variable. The regression results were significant (p=0.0004) with an adjusted r2 of 0.11. All of the independent variables were significant except worker gender. The time period after the control implementation was further investigated, determining the relationship between (ln mercury in urine) vs. (month of the study) using linear regression. The regression results were significant (p<0.0001) with an r2 of 0.42. Using the regression model, 22 months elapsed after the control implementation before the plant mean (ln mercury in urine concentration) dropped to half its original value. As expected, the change in the biological monitoring metric lagged behind the change in area concentration for the time period studied. Limitations on the predictive models include within-worker variability and between-area variability including differences between mercury and nonmercury areas.
K. Hoffner, NJ Laborers Health and Safety Fund, Monroe Township, NJ; K. Hoffman, OSHA, Parsippany, NJ.
A water spray silica dust control for jackhammers was developed by a New Jersey road construction safety partnership two years ago. It reduces respirable silica exposures for road construction workers by 70% to 90%; however, getting the construction industry to use the device has proven more challenging than developing the engineering control itself. This presentation will focus on the methods used to move the control from research to practice. These methods include redesigning the control to make it less expensive for contractors to make; putting together a “How to Make Your Very Own Jackhammer Spray Control” guide for contractors; providing web access to the how-to guide; making up loaner units that contractors can borrow to assess the dust control; promoting use of the control at conferences frequented by contractors, working with the state health department to promote its use on public work jobs; and working with owners of roads and buildings to incorporate use of the control on their construction and maintenance projects. One of the jackhammer spray loaner units will be brought to the presentation for a demonstration, and copies of the how-to guide will be available as well.
P. Susi, Center to Protect Workers’ Rights, Silver Spring, MD; J. Meeker, M. Cooper, University of Michigan, Ann Arbor, MI; C. Cole, Labyrinth Management Group, Medina, OH; M. Flynn, University of North Carolina, Chapel Hill, NC.
Construction workers may be exposed to high airborne silica concentrations. Engineering controls are available for a number of construction tasks and tools but are rarely used. We evaluated commercially available engineering controls for reducing silica exposure during grinding and cutting masonry. All work was conducted by journeymen bricklayers at the International Union of Bricklayers and Allied Crafts (IUBAC) Local 5’s training center in Bordentown, N.J. Exposures associated with use of (1) a portable masonry saw equipped with water, (2) the same saw equipped with local exhaust ventilation (LEV), and (3) a stationary wet saw were compared with the portable masonry saw with no controls for cutting brick and block. For grinding mortar joints, exposures associated with two angle grinders equipped with LEV were compared to the same grinders without controls. Repeat, randomized trials were used for each set of controls and tasks. A personal air sample was collected in the breathing zone of the operator during each trial using a pump calibrated at 4.2 L/min and a GK2.69 respirable/thoracic cyclone from BGI. Sampling media and analysis was in conformance with the NIOSH 7500 method. Real-time monitoring was used to verify respirable dust concentrations, which were cleared between trials. Use of controls tested for cutting block reduced silica exposure by over 90%. Mean exposure without use of controls was 57x the NIOSH recommended exposure limit (REL). Use of controls for cutting brick reduced exposures by 81% to 91%. Mean exposure without use of any control was 19x the REL. Use of controls for grinding resulted in a greater than 90% reduction in silica exposure. Without controls, mean exposure was 218x the NIOSH REL. Tested controls reduced silica exposure dramatically. However, mean exposures were still in excess of the NIOSH REL even with the use of controls.
J. Yoon, H. Choi, Y. Kim, Korea Occupational Safety and Health Agency, Daejeon, Republic of Korea.
The optical lens industry uses lens washing booths and blending processes for monomer resins. In general, auto washing machines and blending processes use hazardous materials, such as acetone and methyl chloride. Particularly in the blending process, workers are excessively exposed to methyl chloride when washing the blending barrels. In an auto washing booth, high-efficiency particulate air (HEPA) filters are installed on the ceiling to supply the clean air in the booth and six exhausts. The filters have two openings (front and rear) for carrying the lens carriage. Vapors of methyl chloride and a mixture of potassium hydroxide and water vapor are inside the booth; therefore, the operating condition is very important to health. If the inlet flow rate from HEPA filters is higher than that of the outlet, indoor workers at the exterior of booth will be exposed to contaminated air. On the contrary, if the outlet flow rate is higher than that of the inlet, the booth pressure will be negative, which causes the inflow of exterior dust. The purpose of these case studies is to assess the air flow pattern in current and optimum operating conditions in auto-washing booth and to find the best condition of HEPA filter’s inlet flow. In this study, the FLUENT computational fluid dynamics (CFD) tool was used to predict airflow pattern in the auto washing booth and the numerical simulation was achieved by applying the κ-ε turbulence model, the Lagrangian particle tracking method. To validate the CFD model, airflow velocity is measured with an anemometer. It was shown that the numerical results reasonably agreed with experimental data for all cases studies. As a result, inlet airflow velocity has a significant impact on the distribution of hazardous materials in a booth and the exterior.
J. Meeker, University of Michigan, Ann Arbor, MI; P. Susi, Center to Protect Workers’ Rights, Silver Spring, MD; C. Cole, Labyrinth Management Group, Medina, OH; M. Flynn, University of North Carolina, Chapel Hill, NC.
Overexposure to welding fume constituents, particularly manganese, is of concern in the construction industry due to the prevalence of welding and the scarcity of engineering controls. We assessed the control effectiveness of a commercially available, portable local exhaust ventilation (LEV) unit, consisting of a portable vacuum and a small bell-shaped hood connected by a flexible 2-in diameter hose, in both experimental and field settings. The experimental testing was done in a semienclosed booth at a pipe-fitter training facility. Five paired trials of LEV control vs. no control, each approximately 1 hr in duration and conducted during two successive welds of 6-in diameter carbon steel pipe, were run in random order. Breathing zone samples were collected outside the welding hood during each trial. In the field scenario, full-shift breathing zone samples were collected from two pipe fitters welding carbon steel pipe for a chiller installation on a commercial construction project. Eight days of full-shift sampling were conducted on both workers (n=16), and the LEV was used by one of the two workers on seven of the days. All samples were collected with personal sample pumps calibrated at 2 L/min. Filter cassettes were analyzed for total particulate and manganese concentration by a certified laboratory. In the experimental setting, use of the portable LEV resulted in a 75% reduction in manganese exposure (mean 13 µg/m3 vs. 51 µg/m3; p<0.05) and a 60% reduction in total particulate (mean 0.74 mg/m3 vs. 1.83 mg/m3; p<0.05). In the field setting, LEV use resulted in a 53% reduction in manganese exposure (geometric mean 46 µg/m3 vs. 97 µg/m3; p<0.05) but only a 10% reduction in total particulate (geometric mean 4.5 mg/m3 vs. 5.0 mg/m3; p>0.05). These results demonstrate that LEV use can reduce manganese exposure in construction. Additional feasibility issues (cost, usability, etc.) will be discussed.
C. Simmons, F. Boelter, M. Weeks, Boelter Associates, Inc., Park Ridge, IL.
An exposure assessment was performed for pipe-fitting activities involving shielded metal arc welding (SMAW, a.k.a. stick welding) on carbon steel. Compounds evaluated included total particulate and various metals. Welding activities were conducted inside a small volume boiler room. During limited time periods, the air in the room was mechanically mixed using several box fans for purposes related to the measurement of the air change rate. At all other times of monitoring, only natural ventilation was available and no mechanical mixing occurred. Because of the small volume of the boiler room and the placement of the fans, active mixing of the room air caused nearly a 100% increase in the airborne concentration of both total particulate and metals. The effects of general exhaust and natural ventilation on airborne exposures to welding fume will be discussed. It was concluded that the difference in results observed with the mixing fans is likely due to the dispersal of welding fumes, which otherwise would have risen past the breathing zone and stratified in the room. With the fans off, the welding plume was observed to rise above the welder’s head and dissipate until it was no longer visible. With the fans on, the welding plume was visibly chaotic. Thus, while the air was being actively mixed with fans, the result was much higher personal breathing zone sample results that were not representative of the welder’s activities. We thus recommend not using mixing fans to evaluate ventilation rates per ASTM methods contemporaneously when conducting an exposure assessment.
WITHDRAWN
D. Leonard, Consultant, Waterford, ME.
Improper selection, poor servicing practices, or inattention to the care and maintenance of portable, high-efficiency (HEPA-/ULPA-filtered) vacuums used for the collection of toxic and/or corrosive materials can pose an exposure hazard to employees and other users as well as a physical risk to property and assets, resulting in noncompliance with relevant health, safety, and environmental regulations. A management program that recognizes worker protection, equipment safety and reliability, and proper waste disposal is crucial to mitigating or greatly reducing these hazards and vulnerabilities. A benchmarking survey of other semiconductor companies revealed that the vacuum management program established at the subject facility is unique in its thoroughness and proactive approach, and that it exceeds others in the measures taken to ensure that vacuum use and maintenance do not present a workplace exposure hazard.
F. Akbar-Khanzadeh, K. Smigielski, University , Toledo, OH.
High-efficiency particulate air (HEPA) filters by definition have an air particle removal efficiency of ≥ 99.97%. Installation of HEPA filters, however, introduces variables that can compromise the filters’ efficiency. The main objective of this research project was to set up a “filter testing unit” to evaluate HEPA filter efficiency in relation to specific installation variables. A closed-system “filter testing unit” was assembled consisting of (1) a fan; (2) an industrial damper; (3) a duct with two ports (one to inject a challenge aerosol and the other to monitor its concentration up-stream from the filter); (4) a filter housing (consisting of a mixing chamber, filter frames equipped with brackets and two ports for measuring and adjusting the pressure-drop across the filter); and (5) a second duct with a port downstream from the filter to monitor the concentration of the challenge aerosol in the filtered air. The concentrations of the challenge aerosol upstream and downstream were used to calculate the filter’s capture efficiency. Eight filters (six HEPA, two non-HEPA) were evaluated based on design principles, particulate capture efficiency, and consistency of effective installation. Each filter was visually inspected to determine the integrity of its outer package, to examine the filter’s structure and texture, and to observe its labels and signs. A significant tear was discovered in one filter, with the damage so extensive that the filter failed the efficiency test. The gaskets of another filter were missing, and without them that filter also failed the efficiency test. The efficiency of filters was determined after the filters were subjected to numerous installation flaw scenarios (including damage to the filter or to the gasket) consistent with situations occurring in the field. The results of this study indicated that any damage of the filter or flaw in the installation process can significantly compromise the performance of HEPA filters.
M. Weeks, C. Simmons, F. Boelter, Boelter Associates, Inc., Park Ridge, IL.
A series of air change rate studies were performed in a single-zone space with varying amounts of that space occupied by objects of known volume. The testing method was based upon ASTM E741-00, Standard Test Method for Determining Air Change in a Single Zone by Means of a Tracer Gas Dilution, using sulfur hexafluoride as a tracer gas. Industrial hygienists often determine the air change rate of a room by calculating V as the overall LxWxH dimensions of the room and then calculating the Q of air entering or leaving the room based on air velocity measurements. In performing these calculations, space in the room that is occupied by machinery, ductwork, or other large objects is often unaccounted for and not included in the kQ/V calculation. Tracer gas methods, such as ASTM E741, are not volume dependent, and they account for directional air movement and “dead air” space, providing a more accurate result. Air change rates were calculated using the ASTM method in a single-zone space at various ventilation rates while occupied by objects of known volume. These air change rates were compared to determine the effect of occupied space. It was found that the percentage of occupied space was approximately proportional to the difference in air change rate, and that this proportion typically held true for different ventilation rates. The importance and relevance of accounting for occupied volume at various air change rates will be discussed, along with the practicalities of determining the amount of occupied space in a field setting. We concluded that when it is necessary to determine the air change rate with a degree of accuracy greater than ±10%, it may be necessary to account for the occupied volume of the space.
M. Weeks, F. Boelter, C. Simmons, Boelter Associates, Inc., Park Ridge, IL.
In a recent study, we determined that valid data may be achievable using ASTM E741-00, Standard Test Method for Determining Air Change in a Single Zone by Means of a Tracer Gas Dilution, with less-than-perfect mixing conditions in a space. A series of air change rate measurements was performed following the ASTM E741-00 method, using sulfur hexafluoride as a tracer gas. The easiest and most direct way to measure air changes per hour (ACH) is by the concentration decay method. However, we found that attempts to use this method for ACH over 20 presented some difficulty. The ASTM method specifically requires a well-mixed room when following any of the methods described in the document. Because of industrial hygiene air sampling activities taking place in the room concurrent to the testing, we had a concern that mechanical mixing using fans could impact the result of our air monitoring. The constant injection method was used along with a novel manifold system we developed to inject tracer gas at seven different locations in the space. To sample the gas, a system of tubing was used to draw samples from five different room locations into a common sampling container. A series of tracer gas measurements was then performed, alternating between mechanically mixed and unmixed conditions to determine the effect of mechanical mixing on the air change rate measurement. We found the final calculations of the tracer gas with and without mixing were in close agreement (<±25%), though the graphs of the measurements looked dissimilar.
R. Morse, D. Zehnter, P. Haas, Morse Zehnter Associates, Troy, NY.
Sustainability involving the use of recycled materials and energy efficiency requiring high levels of insulation are the current trends in architecture. In recent years mold has increasingly become a source for indoor air quality problems in buildings. It is not an accident that this problem is increasing. It is a direct consequence of the way exterior walls are constructed in current practice. In the past, exterior walls were uncomplicated structures without insulation and with vast capability for storing any water that got into the wall assembly. Modern construction methods and materials, combined with the need to insulate, have changed all this. More organic materials that can support mold growth are used in wall construction. Construction practices moving toward lighter assemblies have removed materials that are able to store water that enters the wall. These trends have resulted in a stock of buildings with the potential to be sensitive to moisture problems and mold growth. This session will discuss the differences in construction that have made current construction methods and materials more prone to mold problems, and the way that these problems can be avoided.