T. Courtney, S. Matz, B. Webster, Liberty Mutual, Hopkinton, MA.
The U.S. construction industry increased its share of private sector employment by 11% from 1996 to 2000. Over the same period, its share of private sector injuries and illnesses and cases involving lost time increased by 19 and 23%, respectively. While data on construction injury frequency are reasonably available, less is known about the disability duration due to occupational injuries in construction and the specific events associated with the most disabling traumatic injuries such as fractures. The construction claims experience (n = 35,790) of a large worker’s compensation insurer with national coverage was examined to identify the leading types of disabling occupational morbidity in the U.S. construction industry. Disability duration was calculated from indemnity payments data. Detailed analysis of injury event narratives more specifically classified contributing factors for disabling fractures. The average disability duration for an injured construction worker was 46 days with a median of 0 days. The traumatic injuries with the longest disability durations were fractures of the ankle (median = 55 days), foot (42 days), and wrist (38 days). Falls to a lower level were important contributors to wrist, ankle, and foot fractures and typically involved ladders, scaffolding, and motor vehicles. Struck by incidents were the leading event type for foot fractures and the third most frequent event type for ankle fractures. These incidents involved building materials and, less often, equipment such as jackhammers. Other frequent events resulting in fractures included misstepping on uneven surfaces, slipping and tripping without falling for the ankle and foot, and same level falls for the wrist. Primary prevention resources for slips and falls should be increased and the role of personal protective equipment in preventing fractures re-examined.
D. Sahai, P. Vi, Construction Safety Association of Ontario, Etobicoke, ON, Canada.
In construction, the sanding of drywall compound generates high levels of dust, including respirable silica. Inhaling this dust has been shown to cause eye, nose, throat, and respiratory tract irritation; coughing; phlegm production; and breathing difficulties. Worse, the presence of respirable silica in drywall dust raises the risk of silicosis, pulmonary tuberculosis, chronic obstructive pulmonary disease, and lung cancer. One method of controlling this occupational health hazard is the use of a shrouded ventilated rotary sander (SVRS). This study evaluated, in a controlled environment, the effectiveness of an SVRS in collecting drywall dust. This was done by comparing dust concentrations generated by traditional pole sanding with those generated by an SVRS. Eleven subjects participated in the study, two similar rooms coated with drywall compound were sanded, and a personal aerosol monitor was used to measure respirable dust concentrations. Results indicate that the SVRS can reduce these concentrations by 96%. Silica was detected in the drywall compound used in this study at an average concentration of 5%, making drywall dust control a continuing concern for drywall finishers. To address perceived barriers to wider use of the SVRS, the study also examined the ergonomic implications of rotary versus pole sanding and found that working with the SVRS required less muscular effort. In addition, rather than finding the SVRS heavy, awkward, and difficult to operate, subjects found it on average easier to use than the pole sander.
M. Flanagan, N. Seixas, J. Camp, University of Washington, Seattle, WA; P. Becker, B. Takacs, West Virginia University, Morgantown, WV.
Due to the challenges inherent in collecting personal silica samples on construction sites, most silica exposure assessment studies for construction have had small sample sizes. To increase the depth and breadth of information available on construction silica exposures, the ACGIH Construction Committee undertook a project to solicit silica exposure data from a broad range of sources to compile a more comprehensive data set, and NIOSH supported the analysis. Data were collected from 13 sources including state and federal regulatory agencies (57%), university, government, and federally funded research organizations (34%), and individual construction contractors and consultants (9%). There were 1453 personal samples collected where information was available describing at least the task, trade, or tool associated with the exposure. Information was also collected on controls, nearby dust generation, and environmental conditions when available.
For personal exposures the overall geometric means (GM) were 0.13 mg/m3 (GSD = 5.3) for silica and 1.34 mg/m3 (GSD = 5.5) for respirable dust. Sample duration ranged from 6 to 601 minutes with a median of 219 minutes. Data was grouped by sample duration categories of less than 2 hours, 2–6 hours, and over 6 hours. Concentrations were generally higher at shorter durations. Regulatory sample exposures were higher (GM of 0.16) than research (GM of 0.11) and private (GM = 0.08) sources. For trade, the highest exposures were for abrasive blasters, cement finishers, laborers, and brick masons. Exposures by task and tool were similar with the highest exposures for tuckpoint grinding, surface grinding, abrasive blasting, cutting tunnel/trench, and drilling.
Despite limitations of sample selection and other selection biases, these results indicate that silica overexposures on construction sites occur across several trades and many construction activities and that further control mechanisms are needed to reduce occupational exposure.
S. Collingwood, W. Heitbrink, University of Iowa, Iowa City, IA.
During building renovation, mortar removal with a right angle grinder causes worker exposures to respirable crystalline silica as high as 5 mg/m3, 100 times the NIOSH REL. To control this exposure, vacuum cleaners can be used to exhaust 80 cubic feet per minute (cfm) from a hood that partially encloses the grinding wheel. Prior laboratory studies found that exhaust rates beyond 80 cfm do not yield significant additional reduction in dust emissions. In the laboratory, vacuum cleaner flow rate decreased linearly with increased vacuum cleaner static pressure measured just upstream of the motor. The pressure losses through the hood (including acceleration) was measured to be 1.65 velocity pressures (VP) and measured pressure loss for various hoses was between 0.17 and 0.37 VP/foot. Field trials were conducted to evaluate the ability of vacuum cleaners to maintain flow and to evaluate the exposure outcomes of using these control measures. Flow rates were calculated from the vacuum cleaner static pressures recorded with a data logging 12-bit pressure transducer. When vacuum cleaners were outfitted with 2-inch hoses, they maintained an exhaust volume greater than 80 cfm for a longer time period than when equipped with 1.5-inch diameter hose. As pulverized mortar was collected in the vacuum cleaner, flow rates for vacuum cleaners equipped with 2-inch hose decreased from more than 95 cfm to 65 cfm and when equipped with 1.5-inch diameter hose, the air flows decreased to 40 cfm. Although all vacuum cleaner configurations failed to maintain 80 cfm, geometric mean respirable dust and crystalline silica exposures were 0.95 and 0.07 mg/m3, respectively. Concurrent aerosol photometer and flow rate measurements overlaid onto real-time video suggests that work-practices and the variable gap between the bottom of the hood and the mortar prevents 100% capture of all pulverized mortar.
M. Goldberg, Hunter College-CUNY, New York, NY; K. Wanzer, N. Zuckerman, Mount Sinai Center for Occupational and Environmental Medicine, New York, NY; N. Clark, New York City Department of Health and Mental Hygiene, New York, NY.
We describe and assess a project to develop and evaluate guides to help construction managers and supervisors integrate health hazard controls for lead and silica into infrastructure rehabilitation projects. The “Blueprint Guides” are compiled into a set of best-practice documents outlining the steps required to plan, develop, implement, and evaluate key components of a health hazard control program. Guides are available for exposure assessment, biological monitoring for lead, selecting engineering and work practice controls, respiratory protection, safety meetings, and worker tool box talks. Evaluation of the guides pointed to factors influencing the successful implementation of control programs: the commitment of top management, accountability of managers, expertise and training of construction company personnel, and the extent to which unions and workers are involved in program development and implementation. It was also found that “external” factors are key to managers’ use of the guides, including: the existence of owner specifications for controlling the hazard, the oversight given by the owner to contractor performance, and whether there is an OSHA comprehensive standard. Because the New York City Department of Transportation issues specifications which contain detailed requirements for protecting the environment and workers from lead, and because there is a comprehensive OSHA standard for lead in construction, there was greater incentive on the part of the contractors to use the Blueprint Guides as aids in managing their programs. On the other hand, we found that the silica guides were consulted less frequently. We attribute this to that fact that, while there is an OSHA Special Emphasis Program for Silicosis, there is no comprehensive OSHA standard. In addition, there are no owner specifications for protecting the environment or workers from silica.
J. Meeker, Harvard University, Boston, MA; P. Susi, Center to Protect Workers’ Rights, Silver Spring, MD; A. Pelligrino, New Jersey Department of Transportation, Trenton, NJ.
Objectives: Laboratory studies suggest specular hematite generates significantly lower airborne levels of respirable silica and toxic metals than silica sand and other metal abrasives, respectively. This study evaluated worker exposures to these agents when specular hematite was employed in a field setting.
Methods: Worker exposure monitoring was conducted on four New Jersey pedestrian bridges undergoing renovation. Breathing zone samples were collected outside the blasting hoods of three workers performing abrasive blasting on four nights. Samples were analyzed for total particulate, respirable particulate, respirable silica, hexavalent chromium, and selected metals. Bulk paint chip, clean abrasive, and spent abrasive samples were collected from each bridge and analyzed for crystalline silica and metals content.
Results: Abrasive blasting occurred inside a ventilated containment equipped with a dust collector. Blasting (task) time lasted approximately two hours each night. Task time-weighted average concentrations (geometric mean; range) were obtained (in mg/m3) for total dust (1738.8; 1080–2810), respirable dust (237.8; 62.3–1541), respirable silica (2.69; 0.52–25.7), hexavalent chromium (0.010; <0.001–0.103), arsenic (0.005; <0.001–0.086), beryllium (0.0005; <0.0003–0.0011), cadmium (0.011; 0.003–0.035), total chromium (0.55; 0.29–0.96), lead (56.4; 13.2–307), manganese (0.98; 0.21–6.10), nickel (0.038; 0.011–0.154), silver (0.001; <0.001–0.0037), titanium (0.041; 0.016–0.101), and vanadium (0.005; 0.002–0.031). Paint chip samples from the pre-blasted bridge surface revealed high mean content compared to clean abrasive samples (≥ 10-fold difference) for many of the compounds of interest, including silica, indicating the existing paint contributed significantly to worker exposures.
Conclusion: Specular hematite is likely to create lower worker exposures to specific toxicants compared to other commonly used dry abrasives. However, existing paint can be an important source of exposure to silica and metals, leading to elevated exposures to these toxins even with the use of a less hazardous abrasive media. Due to the potentially hazardous nature of existing paint, other surface preparation techniques should also be evaluated.
S. Levine, University of Michigan, Ann Arbor, MI; J. Thornton, Newport News Shipbuilding, Newport News, VA.
WITHDRAWN
M. Harris, Hamlin & Harris Inc., Baton Rouge, LA; W. Ewing, C. DePasquale, Compass Environmental Inc., Kennesaw, GA; S. Hays, Gobbell Hays Partners Inc., Nashville, TN; W. Longo, R. Hatfield, M. Mount, R. Stapleton, Materials Analytical Services Inc., Suwanee, GA.
This paper describes the results of an evaluation of SMAW welding fume exposures while welding carbon steel in a confined space with varying amounts of mechanically-assisted ventilation. Side-by-side personal and area monitoring with various sampling and analytical techniques was conducted during the SMAW operations. With 2000 cfm dilution ventilation, personal breathing zone samples for the welder were within 75% of the existing TLV® of 0.2 mg/m3 for manganese and were five times greater than the proposed TLV® for respirable manganese of 0.03 mg/m3. Area samples both upstream and downstream of the welder exceeded the existing TLV® of 0.2 mg/m3 for manganese with 2000 cfm dilution ventilation. Air monitoring data from inside and outside the welding helmet do not indicate that this effect is a function of diversion of the plume from the welder’s breathing zone due to the presence of the welding helmet. This study indicates that 2000 cfm general dilution ventilation does not appear to be an appropriate means of controlling respirable manganese exposures for either welders or their helpers in spaces with size and shape characteristics approximating those of the environmental chamber. Air monitoring data showed close agreement between concentrations of respirable manganese and total manganese fume generated by the electrodes used in this study, as well as close agreement between total fume concentrations measured by gravimetric analysis of MWMCE and PVC filter media. Recommendations include additional similar work in confined spaces of varying sizes and configurations to evaluate the extent to which these data are useful in anticipating respirable manganese exposures in other confined spaces. In the absence of site-specific monitoring data that indicates otherwise, it appears prudent to employ respiratory protection or source capture ventilation for SMAW with E6010 or E7018 electrodes rather than depending on 2000 cfm general dilution ventilation in confined spaces.
P. Sriwattanatamma, ExxonMobil Asia Pacific Pte. Ltd., Singapore; A. Fleeger, ExxonMobil Chemical Company, Houston, TX.
Developing a comprehensive industrial hygiene (IH) program for the start-up of any new manufacturing facility can be a very daunting task. Integration into all phases of the project is critical in order to initiate and sustain a successful IH program. This presentation will focus on all phases of the project, including the design, construction, start-up, and ongoing plant operations. We will share the strategy applied and learnings experienced along the way. Specific topics will include:
This approach is a practical example of the steps necessary to develop a baseline IH program that can be applied to any newly-constructed manufacturing facility.
D. Grote Adams, Safex Inc., Westerville, OH.
Situation: Industrial hygienists, because of their unique training and experience, are often used as resources to solve problems that may be indirectly related to reducing employee exposures. Section 510 of the Ohio Mechanical Code requires the use of a hazardous exhaust system if any one of three criteria exist in the facility. The criteria include 25% of the lower explosive limits, chemicals with NFPA health ratings of 4, and 1% of the median lethal concentration.
Problem: Local architects and mechanical engineers need assistance with resolving disputes with the local building code officials.
Resolution: The first case involved a custom vehicle manufacturer. The chemicals in use consisted of welding gases, a spray adhesive, and spray paint cans. The building code inspector initially required the installation of hazardous exhaust systems along each point where the identified chemicals were used. It was determined that this would have been infeasible. With the assistance of the industrial hygienist the manufacturer was able to reach a compromise with the building code inspector that included periodic industrial hygiene monitoring and corrective action if overexposures were identified.
The second case involved a large medical research center. The research center used approximately 40 different chemicals in laboratory scale. The main point of debate was the requirement that when a hazardous exhaust system is installed, it requires separate building shafts for both the air exhaust ducts and the air intake ducts. This would have substantially increased the cost of the five-story 160,000 square foot expansion and put it behind schedule. An industrial hygienist was asked to provide mathematical exposure modeling in order to prove that the medical research center was not in violation.
Benefit to Others: Industrial hygienists will better understand the mechanical code and how they may assist architects and mechanical engineers with code disputes.
Posted May 30, 2004