Range Of Aerosol Concentrations Research Articles

Aerosol physicochemical determinants of carbon black and ozone inhalation co-exposure induced pulmonary toxicity.

Air pollution accounts for more than 7 million premature deaths worldwide. Using ultrafine carbon black (CB) and ozone (O3) as a model for an environmental co-exposure scenario, the dose response relationships in acute pulmonary injury and inflammation were determined by generating, characterizing, and comparing stable concentrations of CB aerosols (2.5, 5.0, 10.0 mg/m3), O3 (0.5, 1.0, 2.0 ppm) with mixture CB + O3 (2.5 + 0.5, 5.0 + 1.0, 10.0 + 2.0). C57BL6 male mice were exposed for 3 h by whole body inhalation and acute toxicity determined after 24 h. CB itself did not cause any alteration, however, a dose response in pulmonary injury/inflammation was observed with O3 and CB + O3. This increase in response with mixtures was not dependent on the uptake but was due to enhanced reactivity of the particles. Benchmark dose modeling showed several-fold increase in potency with CB + O3 compared with CB or O3 alone. Principal component analysis provided insight into response relationships between various doses and treatments. There was a significant correlation in lung responses with charge-based size distribution, total/alveolar deposition, oxidant generation, and antioxidant depletion potential. Lung tissue gene/protein response demonstrated distinct patterns that are better predicted by either particle dose/aerosol responses (interleukin-1β, keratinocyte chemoattractant, transforming growth factor beta) or particle reactivity (thymic stromal lymphopoietin, interleukin-13, interleukin-6). Hierarchical clustering showed a distinct signature with high dose and a similarity in mRNA expression pattern of low and medium doses of CB + O3. In conclusion, we demonstrate that the biological outcomes from CB + O3 co-exposure are significantly greater than individual exposures over a range of aerosol concentrations and aerosol characteristics can predict biological outcome.

A novel approach to calibrating a photoacoustic absorption spectrometer using polydisperse absorbing aerosol

Abstract. A new technique for calibrating photoacoustic aerosol absorption spectrometers with multiple laser passes in the acoustic cavity (multi-pass PAS) has been developed utilizing polydisperse and highly absorbing aerosol. This is the first calibration technique for multi-pass PAS instruments that utilizes particles instead of reactive gases and does not require knowledge of the exact size or refractive index of the absorbing aerosol. In this new method, highly absorbing materials are aerosolized into a polydisperse distribution and measured simultaneously with a multi-pass PAS and a cavity-attenuated phase shift particulate matter single-scattering albedo (CAPS PMSSA, Aerodyne Inc.) instrument. The CAPS PMSSA measures the bulk absorption coefficient through the subtraction of the scattering coefficient from the extinction coefficient. While this approach can have significant errors in ambient aerosol, the accuracy and precision of the CAPS PMSSA are high when the measured aerosol has a low single-scattering albedo (SSA) and particles are less than 300 nm in size, in which case truncation errors are small. To confirm the precision and accuracy of the new calibration approach, a range of aerosol concentrations were sent to the multi-pass PAS and CAPS PMSSA instruments using three different absorbing substances: Aquadag, Regal Black, and Nigrosin. Six repetitions with each of the three substances produced stable calibrations, with the standard deviation of the calibration slopes being less than 2 % at 660 nm and less than 5 % at 405 nm for a given calibration substance. Calibrations were also consistent across the different calibration substances (standard deviation of 2 % at 660 nm and 10 % at 405 nm) except for Nigrosin at 405 nm. The accuracy of the calibration approach is dependent on the SSA of the calibration substance but is roughly 6 % for the calibration substances used here, which all have an SSA near 0.4 at 405 nm. This calibration technique is easily deployed in the field as it involves no toxic or reactive gases and it does not require generation of a monodisperse aerosol. Advantages to this particle-based calibration technique versus techniques based on ozone or nitrogen dioxide absorption include no reactive losses or impact from carrier gases and the broad absorption characteristics of the particles, which eliminate potentially significant errors in calibration that come with small errors in the peak wavelength of the laser light when utilizing gas-phase standards.

Comparison of the efficiency of sampling devices for aerosolized Burkholderia pseudomallei

Previous studies have demonstrated that aerosol sampling devices can have deleterious effects on bacteria due to stresses intrinsic to the sampling processes. Although a significant amount of work has been carried out to develop animal models of inhalational melioidosis, little information has been reported on the effects of the aerosol sampling devices on the causative bacterium, Burkholderia pseudomallei. The aim of this study was to compare the efficiencies for collection of aerosolized bacteria in three sampling devices that have been used in studies utilizing aerosolized B. pseudomallei. The data from this study demonstrate the equivalence of the Mercer impactor, gelatin filter, and model 7541 AGI for sampling respirable aerosols containing B. pseudomallei across a range of aerosol concentrations. It was also determined that the retention efficiency of gelatin filters for culturable B. pseudomallei was near unity, suggesting that desiccation of collected material did not occur for the short sampling period tested. The retention efficiency of the model 7541 AGI for culturable B. pseudomallei was significantly less than unity, and it was determined that this decrease was likely due to the stresses associated with repetitive sampler bubbling. The results of this study also confirmed the results of previous studies on the deleterious effects of the Collison nebulizer on microorganisms and extended these data to include B. pseudomallei.

Radon daughter and thoron daughter deposition velocity and unattached fraction under laboratory-controlled conditions and in underground uranium mines

The deposition velocity and unattached fraction of the short-lived decay products of thoron and radon have been measured in a large (26 m 3) radon/thoron calibration facility and in underground uranium mines. Measurements were conducted under various environmental conditions of relative humidity, temperature, aerosol concentration, and air velocity (0–1.2 m s −1). Unattached fractions were determined using wire screens. Plate-out experiments, carried out to determine deposition velocities, were done using circular stainless steel plates attached to walls. The average RaA unattached fraction in the aerosol concentration range 3.5 × 10 2–1.5 × 10 3 cm −3 was about 0.5. Substantially lower values were obtained for RaB and RaC. Similarly, the average ThB unattached fraction in the same aerosol concentration range was approx. 0.1. Significantly lower values were found for ThC. The unattached fractions in underground uranium mines were considerably lower than the above values, i.e. < 0.01, an experimental result which is consistent with the much higher aerosol concentration in underground working areas. (Experimentally determined radon and thoron daughter deposition velocities were in the range 0.06–0.6 cm/s.) These values are substantially lower than theoretical estimates by Jacobi (0.5–1.5 cm/s) and values used by other authors in the past. Our radon daughter data are, however, in agreement with recent laboratory work by several authors. Deposition velocity and unattached fraction data are relevant for the calculation of daughter product plate-out on mine walls, and hence, for realistic determination of airborne radiation levels in underground uranium mines. This study is of particular interest for some Canadian mines, and other mines, where the presence of thoron and its daughter products is appreciable.