Patrick T. O’Shaughnessy

A Strategy for Assessing Workplace Exposures to Nanomaterials

This article describes a highly tailorable exposure assessment strategy for nanomaterials that enables effective and efficient exposure management (i.e., a strategy that can identify jobs or tasks that have clearly unacceptable exposures), while simultaneously requiring only a modest level of resources to conduct. The strategy is based on strategy general framework from AIHA® that is adapted for nanomaterials and seeks to ensure that the risks to workers handling nanomaterials are being managed properly. The strategy relies on a general framework as the basic foundation while building and elaborating on elements essential to an effective and efficient strategy to arrive at decisions based on collecting and interpreting available information. This article provides useful guidance on conducting workplace characterization; understanding exposure potential to nanomaterials; accounting methods for background aerosols; constructing SEGs; and selecting appropriate instrumentation for monitoring, providing appropriate choice of exposure limits, and describing criteria by which exposure management decisions should be made. The article is intended to be a practical guide for industrial hygienists for managing engineered nanomaterial risks in their workplaces.

Validation of an in vitro exposure system for toxicity assessment of air-delivered nanomaterials.

To overcome the limitations of in vitro exposure of submerged lung cells to nanoparticles (NPs), we validated an integrated low flow system capable of generating and depositing airborne NPs directly onto cells at an air-liquid interface (ALI). The in vitro exposure system was shown to provide uniform and controlled dosing of particles with 70.3% efficiency to epithelial cells grown on transwells. This system delivered a continuous airborne exposure of NPs to lung cells without loss of cell viability in repeated 4h exposure periods. We sequentially exposed cells to air-delivered copper (Cu) NPs in vitro to compare toxicity results to our prior in vivo inhalation studies. The evaluation of cellular dosimetry indicated that a large amount of Cu was taken up, dissolved and released into the basolateral medium (62% of total mass). Exposure to Cu NPs decreased cell viability to 73% (p<0.01) and significantly (p<0.05) elevated levels of lactate dehydrogenase, intracellular reactive oxygen species and interleukin-8 that mirrored our findings from subacute in vivo inhalation studies in mice. Our results show that this exposure system is useful for screening of NP toxicity in a manner that represents cellular responses of the pulmonary epithelium in vivo.

Indoor and outdoor particulate matter and endotoxin concentrations in an intensely agricultural county

The objectives of this study were to characterize rural populations’ indoor and outdoor exposure to particulate matter (PM)10, PM2.5, and endotoxin and identify factors that influence these concentrations. Samples were collected at 197 rural households over five continuous days between 2007 and 2011. Geometric mean (GM) indoor PM10 (21.2 μg/m3) and PM2.5 (12.2 μg/m3) concentrations tended to be larger than outdoor PM10 (19.6 μg/m3) and PM2.5 (8.2 μg/m3) concentrations (PM10 P=0.086; PM2.5 P<0.001). Conversely, GM outdoor endotoxin concentrations (1.93 EU/m−3) were significantly larger than indoor (0.32 EU/m3; P<0.001). Compared with measurements from previous urban studies, indoor and outdoor concentrations of PM10 and PM2.5 in the study area tended to be smaller, whereas ambient endotoxin concentrations measured outside rural households were 3–10 times larger. Contrary to our initial hypothesis, seasonality did not have a significant effect on mean ambient PM10 concentrations; however, endotoxin concentrations in the autumn were almost seven times larger than winter. Excluding home cleanliness, the majority of agricultural and housing characteristics evaluated were found to be poorly associated with indoor and outdoor particulate and endotoxin concentrations.

Murine pulmonary responses after sub-chronic exposure to aluminum oxide-based nanowhiskers.

BackgroundAluminum oxide-based nanowhiskers (AO nanowhiskers) have been used in manufacturing processes as catalyst supports, flame retardants, adsorbents, or in ceramic, metal and plastic composite materials. They are classified as high aspect ratio nanomaterials. Our aim was to assess in vivo toxicity of inhaled AO nanowhisker aerosols.MethodsPrimary dimensions of AO nanowhiskers specified by manufacturer were 2–4 nm x 2800 nm. The aluminum content found in this nanomaterial was 30% [mixed phase material containing Al(OH)3 and AlOOH]. Male mice (C57Bl/6 J) were exposed to AO nanowhiskers for 4 hrs/day, 5 days/wk for 2 or 4 wks in a dynamic whole body exposure chamber. The whiskers were aerosolized with an acoustical dry aerosol generator that included a grounded metal elutriator and a venturi aspirator to enhance deagglomeration. Average concentration of aerosol in the chamber was 3.3 ± 0.6 mg/m3 and the mobility diameter was 150 ± 1.6 nm. Both groups of mice (2 or 4 wks exposure) were necropsied immediately after the last exposure. Aluminum content in the lung, heart, liver, and spleen was determined. Pulmonary toxicity assessment was performed by evaluation of bronchoalveolar lavage (BAL) fluid (enumeration of total and differential cells, total protein, activity of lactate dehydrogenase [LDH] and cytokines), blood (total and differential cell counts), lung histopathology and pulmonary mechanics.ResultsFollowing exposure, mean Al content of lungs was 0.25, 8.10 and 15.37 μg/g lung (dry wt) respectively for sham, 2 wk and 4 wk exposure groups. The number of total cells and macrophages in BAL fluid was 2-times higher in animals exposed for 2 wks and 6-times higher in mice exposed for 4 wks, compared to shams (p < 0.01, p < 0.001, respectively). However no neutrophilic inflammation in BAL fluid was found and neutrophils were below 1% in all groups. No significant differences were found in total protein, activity of LDH, or cytokines levels (IL-6, IFN-γ, MIP-1α, TNF-α, and MIP-2) between shams and exposed mice.ConclusionsSub-chronic inhalation exposures to aluminum-oxide based nanowhiskers induced increased lung macrophages, but no inflammatory or toxic responses were observed.

A Novel Device for Measuring Respirable Dustiness Using Low Mass Powder Samples

Respirable dustiness represents the tendency of a powder to generate respirable airborne dust during handling and therefore indicates the propensity for a powder to become an inhalation hazard. The dustiness of 14 powders, including 10 different nanopowders, was evaluated with the use of a novel low-mass dustiness tester designed to minimize the use of the test powder. The aerosol created from 15-mg powder samples falling down a tube were measured with an aerodynamic particle sizer (APS). Particle counts integrated throughout the pulse of aerosol created by the falling powder were used to calculate a respirable dustiness mass fraction (D, mg/kg). An amorphous silicon dioxide nanopowder produced a respirable D of 121.4 mg/kg, which was significantly higher than all other powders (p < 0.001). Many nanopowders produced D values that were not significantly different from large-particle powders, such as Arizona Road Dust and bentonite clay. In general, fibrous nanopowders and powders with primary particles >100 nm are not as dusty as those containing granular, nano-sized primary particles. The method used here, incorporating an APS, represents a deviation from a standard method but resulted in dustiness values comparable to other standard methods.

Distribution of Particle and Gas Concentrations in Swine Gestation Confined Animal Feeding Operations

OBJECTIVES Dust mass concentrations, temperatures, and carbon dioxide concentrations were mapped in a modern, 1048-pen swine gestation barn in winter, spring, and summer. METHODS In each season, two technicians measured respirable mass concentrations with an aerosol photometer and temperatures and carbon dioxide concentrations with an indoor air quality monitor at 60 positions in the barn. Stationary photometers were also deployed to measure mass concentrations during mapping at five fixed locations. RESULTS In winter when building ventilation rates were low (center-barn mean air velocity=0.34 m s(-1), 68 fpm) to conserve heat within the barn, mass and carbon dioxide concentrations were highest (mass geometric mean, GM=0.50 mg m(-3); CO2 GM=2060 ppm) and fairly uniform over space (mass geometric standard deviation, GSD=1.48; CO2 GSD=1.24). Concentrations were lowest in summer (mass GM=0.13 mg m(-3); CO2 GM=610 ppm) when ventilation rates were high (center-barn mean air velocity=0.99 m s(-1), 196 fpm) to provide cooling. Spatial gradients were greatest in spring (mass GSD=2.11; CO2 GSD=1.50) with low concentrations observed near the building intake, increasing to higher concentrations at the building exhaust. CONCLUSIONS Mass concentrations obtained in mapping were generally consistent with those obtained from stationary monitors. A moderately strong linear relationship (R2=0.60) was observed between the log of photometer-measured mass concentration and the log of carbon dioxide concentration, suggesting that carbon dioxide may be an inexpensive alternative to assessing air quality in a swine barn. These results indicate that ventilation can effectively reduce contaminant levels in addition to controlling temperature.

Titanium Dioxide Nanoparticles: Grassian et al. Respond

Baveye and Laba have further analyzed the transmission electron micrograph (TEM) image shown in Figure 2A of our article (Grassian et al. (2007b) to quantitatively determine the extent of titanium dioxide nanoparticle clustering in the image by calculating the radial distribution function. The main point of doing this calculation was to demonstrate that TiO2 nanoparticle aggregates will not completely deaggregate even when subjected to harsh conditions.

Performing T-tests to Compare Autocorrelated Time Series Data Collected from Direct-Reading Instruments

Industrial hygienists now commonly use direct-reading instruments to evaluate hazards in the workplace. The stored values over time from these instruments constitute a time series of measurements that are often autocorrelated. Given the need to statistically compare two occupational scenarios using values from a direct-reading instrument, a t-test must consider measurement autocorrelation or the resulting test will have a largely inflated type-1 error probability (false rejection of the null hypothesis). A method is described for both the one-sample and two-sample cases which properly adjusts for autocorrelation. This method involves the computation of an “equivalent sample size” that effectively decreases the actual sample size when determining the standard error of the mean for the time series. An example is provided for the one-sample case, and an example is given where a two-sample t-test is conducted for two autocorrelated time series comprised of lognormally distributed measurements.

Evaluation of the Filtration Efficiency of the N95 Filtering Facepiece Respirator for Airborne Methicillin-Resistant Staphylococcus aureus

Abstract. Airborne methicillin-resistant Staphylococcus aureus (MRSA) was detected inside a swine facility that presented a risk of respiratory colonization and infection to swine and swine workers. Viable airborne MRSA was sampled using an Andersen cascade impactor, and total airborne particulates were sampled using an optical particle counter. The filter efficiency of the N95 filtering facepiece respirator (FFR) was evaluated to determine its effectiveness for airborne MRSA. Our study showed that the filter for the N95 FFR had efficiency greater than 95% for airborne MRSA.