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The goal of this study was to reconstruct the historical respirable silica (RS) and respirable dust (RD) exposures of workers in the Minnesota taconite industry from 1955 to 2010 as part of several epidemiological studies for assessing the association between exposure to components of taconite dusts and the development of respiratory diseases. A job-exposure matrix (JEM) was developed that uses 9127 RS and 19 391 RD occupational hygiene historical measurements. Historical RS and RD data were extracted from several sources and were grouped into seven mines and then into eight departments [Concentrating, Crushing, Janitor, Mining, Office/control room, Pelletizing, Shop (mobile), and Shop (stationary)]. Within each department, we applied a two-level random-intercept regression model which assumes that the natural log of Y (RD or RS concentration) changes over time at a constant rate. Among all predicted RD and RS values, we found that larger RD values were located in the following departments: Crushing, Concentrating, Pelletizing, and Shop (mobile). Larger RS values were located only in either Crushing or Shop (mobile). The annual rates of change for historical RD and RS exposures were between −3.3 and 3.2%. The silica percentage in the dust varied by mine/department with the highest value of 29.3% in Mine F (Crushing) and the lowest value of 2.1% in Mine B (Pelletizing). The predicted historical RD and RS arithmetic mean exposures ranged between <0.075 and 3.14 mg m−3, and between <0.005 and 0.36 mg m−3, respectively. The result of this study is a JEM by mine, department, and year for RD and RS for epidemiological studies. [ABSTRACT FROM AUTHOR]

Studies in environmental epidemiology and of occupational cohorts have implicated the effects of fine particulates with increased risk of cardiovascular diseases. Motivated by this evidence, we conducted an ambient air monitoring campaign to characterize fine aerosol concentrations around various taconite ore processes in six taconite mines in northeastern Minnesota. The ore processes were first categorized into 16 broad work areas/buildings. We then took air samples at 91 fixed locations using an array of direct-reading instruments to obtain measurements of mass (PM2.5 or particles with aerodynamic diameter <2.5 µm, and respirable particulate matter or RPM), alveolar-deposited surface area (ADSA), and particle number (PN) concentrations. At each location, a respirable gravimetric pump (which was used for calibration purposes) and the instruments measured the ambient dust level for 4 h producing ~240 1-min averaging real-time measurements. To analyze these data, we fit a Bayesian hierarchical model with an autoregressive order 1 correlation structure to estimate pooled concentrations for the 16 work areas/buildings while accounting for temporal correlation. PM2.5 and RPM average ambient concentrations were highly correlated to each other (Pearson's correlation = 0.98), followed by ADSA and PN correlation (R = 0.77). Office and control room areas were found to have the lowest concentrations in all four metrics when compared to other groups. Distinguishing between concentration levels among the remaining groups was more difficult due to the high uncertainty associated with the geometric mean estimates. The geometric standard deviation within location (GSDWL) generally ranged from 1 to 3 for all exposure metrics, except for a few locations that may have had changes in the work activities that generated the observed peaks and variability during the sampling duration. The geometric standard deviation between locations estimates were generally higher than GSDWL, which may indicate larger variability in the processes/activities between locations within each broad work area/building. Future work may look into whether it is feasible to use area measurements for epidemiological investigation and use personal measurements (if available) to validate such approach. [ABSTRACT FROM AUTHOR]

Objective: Evolving production practices in the swine industry may alter the working environment. This research characterized the influence of stall versus pen gestation housing and wet versus dry feed in finishing on air contaminant concentrations. Methods: Eight-hour time-weighted ammonia, hydrogen sulfide, respirable dust, respirable endotoxin, and carbon dioxide concentrations and temperature were measured regularly at stationary locations throughout a year in a facility with parallel gestation stall and open pen housing and parallel finishing rooms using dry and wet feed delivery systems. Hazard indices were calculated using ammonia, hydrogen sulfide, and endotoxin concentrations and relevant occupational exposure limits. Statistical analyses were performed to assess the influence of time of year, housing, and feed on measured parameters. Results: Due to reductions in ventilation rates as outdoor temperatures decreased, season affected pollutant levels more than other factors, with concentrations approximately one order of magnitude greater in winter than during summer. Ammonia, dust, and endotoxin were 25%, 43%, and 67% higher, respectively, on average, in the room with gestation pens than in the room with stalls. Endotoxin concentrations were more than five times higher, on average, with the dry feed system than with wet feed. While individual contaminant concentrations were generally below regulatory limits, hazard index calculations suggest that the effects of combined exposures on respiratory health may present a risk to workers. Elevated levels of respirable endotoxin and hydrogen sulfide were observed during power washing. Conclusions: Ventilation changes in response to seasonal requirements influenced air contaminant concentrations more than production practices, especially housing type. Wet feed systems substantially reduced airborne endotoxin concentrations. [ABSTRACT FROM AUTHOR]

This study assessed the present-day levels (year 2010–2011) of exposure to respirable dust (RD) and respirable silica (RS) in taconite mines and evaluated how the mining process influences exposure concentrations. Personal samples (n = 679) were collected to assess exposure levels of workers to RD and RS at six mines in the Mesabi Iron Range of Minnesota. The RD and RS concentrations were measured using the National Institute for Occupational Safety and Health (NIOSH) 0600 and NIOSH 7500, respectively. Between-mine, between-SEG (similar exposure groups), within-SEG, and within-worker components of variability for RD and RS exposures were estimated using a two- or three-way nested random-effects ANOVA model. The majority of RD concentrations across all mines were below the Mine Safety and Health Administration (MSHA) Permissible Exposure Limit (PEL). The highest concentrations of RD were often observed in either thePelletizingorCrushingdepartments, which are inherently dusty operations. With a few exceptions, the concentrations of RS in the crushing and concentrating processes were higher than those in the other mining processes, as well as higher than the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV) for RS. The magnetic separation and flotation processes in the concentrating department reduced the levels of RS significantly, and lowered the percentage of quartz in RD in the pelletizing department. There was little variability among the six mines or between the two mineralogically distinct zones for either RD or RS exposures. The between-SEG variability for RS did not differ substantially across most of the mines and was a major component of exposure variance. The within-SEG (or between-worker) variance component was typically the smallest because in many instances one worker from a SEG within a mine was monitored multiple times. Some of these findings were affected by the degree of censoring in each SEG and mine, characteristics of the taconite rock, seasonal effects during sampling, or the tasks assigned to each job in that mine. [ABSTRACT FROM PUBLISHER]

This research measured the effects of particle diameter, surfactant-containing spray solution, and particle charge on the capture of respirable particles by surfactant-containing water spray droplets. Polystyrene latex particles with diameters of 0.6, 1.0, or 2.1 μm were generated in a wind tunnel. Particles were given either a neutralized, unneutralized, net positive, or net negative charge, and then were captured as they passed through sprays containing anionic, cationic, or nonionic surfactant. The remaining particles were sampled, charge-separated, and counted with the sprays on and off at varying voltage levels to assess collection efficiency. Overall efficiencies were measured for particles with all charge levels, as well as efficiencies for particles with specific charge levels. The overall collection efficiency significantly increased with increasing particle diameter. Collection efficiencies of 21.5% ± 9.0%, 58.8% ± 12.5%, and 86.6% ± 43.5% (Mean ± SD) were observed for particles 0.6, 1.0, and 2.1 μm in diameter, respectively. The combination of surfactant classification and concentration also significantly affected both overall spray collection efficiency and collection efficiency for particles with specific charge levels. Ionic surfactant-containing sprays had the best performance for charged particles with the opposite sign of charge but the worst performance for charged particles with the same sign of charge, while nonionic surfactant-containing spray efficiently removed particles carrying relatively few charges. Particle charge level impacted the spray collection efficiency. Highly charged particles were removed more efficiently than weakly charged particles. [ABSTRACT FROM PUBLISHER]

The article reports on the study that focused on bioaerosol filtration and respiratory protection against airborne microorganisms. The researchers consider heating, ventilating, and air-conditioning (HVAC) filters as long-term integrated samplers of biological particles which may be released intentionally or unintentionally into a public building. It discusses the concepts of sampling bioaerosols by inertial impaction, centrifugal removal, and liquid impingement. Moreover, it demonstrates that the vegetative cells could be successfully eluted from HVAC filters even if they do not maintain their culturability.

An abstract of the article "Characterization of Air Contaminants Associated with Type of Swine Production Facilities" by Darby Murphy, Shannon Engelman and Peter C. Raynor is presented.