W. Heitbrink, T. Peters, University of Iowa, Iowa City, IA; D. Evans, CDC, Cincinnati, OH; T. Slavin, Navistar-International, Warrenville,, IL.
Aerosol instrumentation was used to characterize fine particle number and respirable mass concentrations in a truck engine plant. This plant encompassed over 100,000 m2 in three primary work areas: the cam-crank area; the block-head-rod area; and the assembly area. A condensation particle counter (CPC: 0.01 µm to 1 µm) and an optical particle counter (OPC: 0.3 µm to 20 µm) were used to measure particle number concentration in a predetermined grid within the plant on multiple days during winter and summer. Aerosol maps were created from these data. An Electrical Low Pressure Impactor was used in selected locations to measure particle size distribution from 0.007 µm to 10 µm in 12 channels. Direct, gas-fired heaters caused elevated CPC concentrations in the winter. During the winter, the CPC concentrations were approximately 106 particles/cm3 in the block-head-rod area versus 3×105 particles/cm3 in other areas. During the summer, the CPC concentrations were about 5×104 particles/cm3 regardless of location. The count mode of the particles from the direct, gas-fired heaters was between 0.007 to 0.05 µm. Respirable mass concentrations did not vary with season and were attributed to mist leaking from the old enclosures in the cam-crank line. The mist concentration in the cam-crank line was 0.12 mg/m3 versus 0.03 mg/m3 in the assembly area. The count mode of the aerosol generated by the machining operations was in the 0.01 to 0.1 µm range. However, the most of the mass was in the 2–20 µm range.
S. Trakumas, P. Hall, D. Smith, SKC Inc., Eighty Four, PA.
Personal size selective samplers available presently only follow approximately the respirable or thoracic curves defined by ACGIH and ISO. In most cases, these samplers oversample smaller particles and undersample larger ones. Therefore, more accurate sampling methods are in demand to better assess worker exposure to respirable or thoracic dust. Newly developed Parallel Particle Impactors are available with respirable or thoracic cut-off. Each model contains four separate impactors arranged in parallel. Each impactor has an inlet nozzle, collection plate, and outlet orifice. The inlet nozzle of each impactor is sized to achieve the desired particle cut (model dependent). Outlet orifices are complementary to inlet nozzles so that the flow rate through each impactor is equal (one-fourth the entire flow through the sampler). The cut-off size for each impactor is selected so that each impactor simulates a different segment (one quarter) of the preselected curve resulting in an overall performance of the sampler that follows closely the respirable or thoracic curve (model dependent). Respirable and thoracic Parallel Particle Impactor models operating at 2.0 L/min flow rate were evaluated in a test chamber using an Aerodynamic Particle Sizer. Potassium sodium tartrate, dioctyl phthalate, glass spheres, and coal mine dust were used as test aerosol. Data indicate that the performance of the respirable and thoracic Parallel Particle Impactors are in good agreement with their respective ACGIH/CEN/ISO conventions and sampling efficiency is not dependent on the type of particle collected. Experiments revealed that a load of approximately 6.4 mg of coal mine dust on the sampler impaction plates did not adversely affect the performance of the Parallel Particle Impactor. A performance comparison of the new samplers with other commercially available size-selective samplers indicates that the Parallel Particle Impactors match the entire respirable or thoracic curves more closely than other samplers available.
C. Dion, S. Viau, Y. Cloutier, IRSST, Montreal, PQ, Canada; A. Dufresne, McGill University, Montreal, PQ, Canada; G. Perrault, Consultant, Montreal, PQ, Canada.
Two different assessments were done in an aluminum smelter during two clustered periods of three days in the work area where the task consists of cleaning the top of used anodes (anode butts), eliminating residues of solid electrolytic bath. Beryllium content in supplied alumina changed from near 3 ppm to < 1 ppm. The main objective of this study was to examine the effect of Be content in alumina on the airborne Be concentration. Sampling was performed according to total and inhalable sampling methods. Samples were analysed for gravimetric results and Be contents according to NIOSH methods 0600 and 7300. For total dust Geometric Means (GMs), there was no statistical difference between the two assessments: 4.1 mg/m3 (n=14) and 3.9 mg/m3 (n=5) (p=0.85) nor with inhalable dust: 5.9 mg/m3 (n=10) and 6.8 mg/m3 (n=7) (p=0.59). However, GM of total Be dust concentration in the first assessment, 0.34 µg/m3 (n=14), was higher than in the second, 0.19 µg/m3 (n=5) (p=0.05). The trend was similar for GM of inhalable Be dust with 0.49 µg/m3 (n=10) versus 0.33 µg/m3 (n=7) although not statistically significant (p=0.23). The ratio of Be to dust concentrations for total dust in the first assessment (0.009%) was different from the second (0.005%) (p=0.001) and the same ratios were observed for inhalable dust (p=0.034). Although we have a limited number of samples, airborne Be concentration from personal samples are in line with ambient samples. Be concentration in supplied alumina could be a determinant factor for airborne Be concentrations.
B. Pacolay, NIOSH, Morgantown, WV.
Lead is mined in association with zinc and silver. The ore is concentrated on site by crushing and differential flotation before being sent to a primary smelter. Personal and area samples for airborne lead were taken at a lead mine concentrator mill. Zinc and iron were also present in all the airborne dusts. Samplers used included the closed-face 37mm filter cassette (the current U.S. standard method for lead sampling), the 37mm GSP or “cone” sampler, the 25mm Institute of Occupational Medicine (IOM) inhalable sampler, the 25mm button sampler, and the open-face 25mm cassette. The mixed cellulose-ester filters were analyzed after sampling for their content of various metals, particularly lead, using a portable x-ray fluorescence (XRF) analyzer, and then were extracted with acid and analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES). The 25-mm filters were analyzed using a single XRF reading, while three readings on different parts of the filter were taken from the 37-mm filters. For lead, all five samplers gave good correlations (r2 > 0.96) between the two analytical methods over the entire range of found lead mass, which encompassed the PEL enforced by MSHA. Linear regression on the results from most samplers gave almost 1:1 correlations without additional correction, indicating an absence of matrix effects from the other metals. As in previous studies, the best results were obtained with the GSP sampler using the average of three readings, with all XRF results within 20% of the corresponding ICP values and a slope very close to 1 (0.99). Greater than 95% of XRF results were within 20% of the corresponding ICP values for the closed-face 37mm cassette using an algorithm developed by OSHA. A considerable portion of total particulate aspiration was found deposited the interior walls of all samplers that possessed a suitable internal surface.
G. Mainelis, M. Yao, Rutgers University, New Brunswick, NJ.
Portable microbial samplers are increasingly used for determining exposure to
biological aerosols. However, only limited information is available about the
performance characteristics of such samplers. Thus, the objective of this study
was to investigate the physical collection efficiencies of several portable
microbial samplers when collecting inhalable biological and nonbiological
particles and to determine their conformity to inhalation convention.
The tested samplers included RCS HighFlow, BioCulture, Microflow,
Microbiological Air Sampler, SMA MicroPortable, SAS Super 180, and Millipore Air
Tester. All these samplers collect biological particles on agar media and their
built-in sampling flow rates range from 30 to 180 L/min. The physical collection
efficiencies of the samplers were determined using polystyrene latex particles
ranging from 0.5 to 5.2 µm in aerodynamic size and six species of bacteria and
fungi ranging in aerodynamic diameter from 0.6 to 3.2 µm. The collection
efficiency was determined by isokinetically measuring particle concentrations
upstream and downstream of the samplers and also separately determining particle
losses inside the samplers due to air movers positioned behind the collection
media. Experimental results have shown that all evaluated samplers collect less
than 10% of 0.5 µm particles. The effective d50, or cut-off sizes, of the
investigated samplers depended on the sampler model and ranged from 1.2 µm for
the RCS High Flow operating at 100 L/min to above 5.2 µm (SMA Microportable
operating at 141.5 L/min, BioCulture operating at 120 L/min, and Microflow
operating at 120 L/min). Compari-son of the samplers’ collection characteristics
with the sampling convention for total inhalable particles revealed that
relative to the inhalation convention most of the investigated portable
microbial samplers would under-sample investigated particles including tested
bacteria and fungi. The obtained results indicate that application of the tested
portable bioaerosol samplers for biological exposure assessment may result in
underestimation of the inhalable airborne microorganism concentrations.
K. Henry, C. Brossia, Amgen, Longmont, CO.
After conducting a process overview of the cell processing area of a biotechnology company and IH sampling, it was discovered that elevated levels of endotoxins were present in such processing area. Through sampling it was determined that the endotoxins were becoming airborne from several sources including open piping, which expelled debris into a floor drain, along with intermittent air pressure releases within a centrifuge. Research on endotoxins is limited, and the available data varied greatly in recommended exposure limits. Also, it was impossible to completely engineer out all releases of endotoxin due to the necessity of a pressure release for the centrifuge operation. Endotoxin exposures needed to be characterized in several areas (large scale manufacturing as well as pilot scale). As a result of outside consultation with an occupational physician specializing in endotoxins, an occupational exposure limit (OEL) was established. Initial engineering controls, which included piping modifications, were utilized to enclose open space between the biowaste pipe and the drain. While these engineering controls reduced airborne endotoxin concentrations levels, they did not decrease the endotoxin levels to the OEL. Accordingly, a mandatory respiratory program was implemented for employees working in the cell processing area. The program included medical surveillance consisting of PFT and physicals every six months to monitor lung capacity changes. Subsequent engineering modifications were successful in lowering exposures below the OEL and respirators were eliminated. Lessons learned were successfully implemented in a pilot plant. The case study provides an excellent example of many of the key steps in practical industrial hygiene, along with information regarding the assessment of endotoxins, a somewhat “new” occupational exposure outside agriculture settings.
Posted May 30, 2006