Lupita D. Montoya

Short-term dynamics of indoor and outdoor endotoxin exposure: Case of Santiago, Chile, 2012

Indoor and outdoor endotoxin in PM2.5 was measured for the very first time in Santiago, Chile, in spring 2012. Average endotoxin concentrations were 0.099 and 0.094 [EU/m(3)] for indoor (N=44) and outdoor (N=41) samples, respectively; the indoor-outdoor correlation (log-transformed concentrations) was low: R=-0.06, 95% CI: (-0.35 to 0.24), likely owing to outdoor spatial variability. A linear regression model explained 68% of variability in outdoor endotoxins, using as predictors elemental carbon (a proxy of traffic emissions), chlorine (a tracer of marine air masses reaching the city) and relative humidity (a modulator of surface emissions of dust, vegetation and garbage debris). In this study, for the first time a potential source contribution function (PSCF) was applied to outdoor endotoxin measurements. Wind trajectory analysis identified upwind agricultural sources as contributors to the short-term, outdoor endotoxin variability. Our results confirm an association between combustion particles from traffic and outdoor endotoxin concentrations. For indoor endotoxins, a predictive model was developed but it only explained 44% of endotoxin variability; the significant predictors were tracers of indoor PM2.5 dust (Si, Ca), number of external windows and number of hours with internal doors open. Results suggest that short-term indoor endotoxin variability may be driven by household dust/garbage production and handling. This would explain the modest predictive performance of published models that use answers to household surveys as predictors. One feasible alternative is to increase the sampling period so that household features would arise as significant predictors of long-term airborne endotoxin levels.

Effect of particle size on in vitro cytotoxicity of titania and alumina nanoparticles

Aluminium oxide (Al2O3) and titanium dioxide (TiO2) nanoparticles (NPs) have been widely used in nanotechnology-based products. Recently, researchers and the public have raised concerns about the adverse effects of these NPs in biological systems, particularly in humans. The aim of this study was to investigate the possible adverse effects of these two common metal oxide NPs on human lung epithelium cells (A549) and to investigate NP size-dependent effects on these cells, considering both the primary and hydrodynamic particle size. NPs were found to inhibit cell viability and proliferation at the highest concentration level (10 mg/mL) included in this study, as measured by a clonogenic assay. Moreover, cell viability, proliferation and metabolism were impaired to a greater extent by the smaller NPs (5 nm TiO2 and 10 nm Al2O3) relative to the larger particles (200 nm TiO2 and 50 nm Al2O3) included in this study, as measured by cell proliferation and metabolism. Notably, the observed cytotoxic effects correlated to the primary size, rather than the hydrodynamic size. Similarly, NP cytotoxicity was found to be correlated with the NP surface area. These findings highlight the importance of including primary size and surface area information in NP characterisation in cytotoxicity studies.

Emission factors of fine particulate matter, organic and elemental carbon, carbon monoxide, and carbon dioxide for four solid fuels commonly used in residential heating by the U.S. Navajo Nation

ABSTRACT Most homes in the Navajo Nation use wood as their primary heating fuel, often in combination with locally mined coal. Previous studies observed health effects linked to this solid-fuel use in several Navajo communities. Emission factors (EFs) for common fuels used by the Navajo have not been reported using a relevant stove type. In this study, two softwoods (ponderosa pine and Utah juniper) and two high-volatile bituminous coals (Black Mesa and Fruitland) were tested with an in-use residential conventional wood stove (homestove) using a modified American Society for Testing and Materials/U.S. Environmental Protection Agency (ASTM/EPA) protocol. Filter sampling quantified PM2.5 (particulate matter with an aerodynamic diameter ≤2.5 μm) and organic (OC) and elemental (EC) carbon in the emissions. Real-time monitoring quantified carbon monoxide (CO), carbon dioxide (CO2), and total suspended particles (TSP). EFs for these air pollutants were developed and normalized to both fuel mass and energy consumed. In general, coal had significantly higher mass EFs than wood for all pollutants studied. In particular, coal emitted, on average, 10 times more PM2.5 than wood on a mass basis, and 2.4 times more on an energy basis. The EFs developed here were based on fuel types, stove design, and operating protocols relevant to the Navajo Nation, but they could be useful to other Native Nations with similar practices, such as the nearby Hopi Nation. Implications: Indoor wood and coal combustion is an important contributor to public health burdens in the Navajo Nation. Currently, there exist no emission factors representative of Navajo homestoves, fuels, and practices. This study developed emission factors for PM2.5, OC, EC, CO, and CO2 using a representative Navajo homestove. These emission factors may be utilized in regional-, national-, and global-scale health and environmental models. Additionally, the protocols developed and results presented here may inform on-going stove design of the first EPA-certified wood and coal combination stove.

Design and Characterization of a New Coarse Particle Collector Based on Microtrap Impactor Technology

A microtrap inertial impactor has been developed and characterized for use as an area or personal sampler. The microtrap impactor utilizes a high-density multijet plate to direct airflow and a matched multiwell plate to impact and collect particles for extraction with a reduced pressure drop relative to inertial impactors with fewer jets. Reported here is the characterization of the microtrap impactor using a fluidized bed aerosol generator and a small volume nebulizer to generate particles of Arizona Road Dust, potassium chloride, and oleic acid. Collection efficiency was determined by measuring particle size distributions with an aerodynamic particle sizer. Two geometries of the microtrap were tested suitable for a two-stage coarse particle sampler, with 1–4 μm and a 4–10 μm stages. The 1 μm cut-point microtrap stage has a collection efficiency above 97% for particles greater than 2 μm in diameter (at a 10 L/min flow rate and a pressure drop of 0.12 kPa). This stages collection efficiency was constant for a period of time up to 10 h under typical ambient conditions without any coating on the impaction surface. The microtrap impactor provides an improvement in area sampling due to its high collection efficiency at a low pressure drop across the device, and its use of an uncoated impaction surface allowing for the extraction and analysis of biological samples.

Indoor PM 2.5 in an urban zone with heavy wood smoke pollution: The case of Temuco, Chile

Temuco is a mid-size city representative of severe wood smoke pollution in southern Chile; however, little is known about the indoor air quality in this region. A field measurement campaign at 63 households in the Temuco urban area was conducted in winter 2014 and is reported here. In this study, indoor and outdoor (24-hr) PM2.5 and its elemental composition were measured and compared. Infiltration parameters and outdoor/indoor contributions to indoor PM2.5 were also determined. A statistical evaluation of how various air quality interventions and household features influence indoor PM2.5 was also performed. This study determined median indoor and outdoor PM2.5 concentrations of 44.4 and 41.8 μg/m3, respectively. An average infiltration factor (0.62 ± 0.06) was estimated using sulfur as a tracer species. Using a simple mass balance approach, median indoor and outdoor contributions to indoor PM2.5 concentrations were then estimated as 12.5 and 26.5 μg/m3, respectively; therefore, 68% of indoor PM2.5 comes from outdoor infiltration. This high percentage is due to high outdoor pollution and relatively high household air exchange rates (median: 1.06 h-1). This study found that S, Br and Rb were dominated by outdoor contributions, while Si, Ca, Ti, Fe and As originated from indoor sources. Using continuous indoor and outdoor PM2.5 measurements, a median indoor source strength of 75 μg PM2.5/min was estimated for the diurnal period, similar to literature results. For the evening period, the median estimate rose to 135 μg PM2.5/min, reflecting a more intense wood burning associated to cooking and space heating at night. Statistical test results (at the 90% confidence level) support the ongoing woodstove replacement program (reducing emissions) and household weatherization subsidies (reducing heating demand) for improving indoor air quality in southern Chile, and suggest that a cookstove improvement program might be helpful as well.

CHAPTER 10:Aerosol Physics for Bioaerosols

Bioaerosols commonly occur as airborne particles that consist of, or originate from, living organisms. They are ubiquitous in the environment and have significant health impacts that range from the mild, such as allergic reactions, to the severe, including asthma and cancer. Bioaerosols have unique and varied physical, chemical and biological properties that affect their movement and interactions within their surrounding ecological systems and are generally categorized based on their physical (e.g. micron, submicron, nanometer size) and biological (e.g. viable, nonviable, culturable) properties. These properties directly impact their behavior in air, including how long they remain airborne, their deposition in the respiratory tract, binding with other particles and surfaces, etc. This chapter discusses how to characterize bioaerosols in terms of their particle size distribution, shape, density, surface area, mass and concentration. Equations are presented for calculating particle movement in air that take into account particle relaxation time and terminal settling velocity, a slip correction factor for small particles, dynamic shape factor corrections for irregularly shaped particles and aerodynamic particle size. This information is provided to give the reader the necessary tools to predict the behavior of bioaerosols and to understand better their impact on human health.