Sources and dynamics of fluorescent particles in hospitals.

Fluorescent particles can be markers of bioaerosols and are therefore relevant to nosocomial infections. To date, little research has focused on fluorescent particles in occupied indoor environments, particularly hospitals. In this study, we aimed to determine the spatial and temporal variation of fluorescent particles in two large hospitals in Brisbane, Australia (one for adults and one for children). We used an Ultraviolet Aerodynamic Particle Sizer (UVAPS) to identify fluorescent particle sources, as well as their contribution to total particle concentrations. We found that the average concentrations of both fluorescent and non-fluorescent particles were higher in the adults' hospital (0.06×106 and 1.20×106  particles/m3 , respectively) than in the children's hospital (0.03×106 and 0.33×106  particles/m3 , respectively) (P<.01). However, the proportion of fluorescent particles was higher in the children's hospital. Based on the concentration results and using activity diaries, we were able to identify sources of particle production within the two hospitals. We demonstrated that particles can be easily generated by a variety of everyday activities, which are potential sources of exposure to pathogens. Future studies to further investigate their role in nosocomial infection are warranted.

Chamber bioaerosol study: human emissions of size-resolved fluorescent biological aerosol particles.

Humans are a prominent source of airborne biological particles in occupied indoor spaces, but few studies have quantified human bioaerosol emissions. The chamber investigation reported here employs a fluorescence-based technique to evaluate bioaerosols with high temporal and particle size resolution. In a 75-m(3) chamber, occupant emission rates of coarse (2.5-10 µm) fluorescent biological aerosol particles (FBAPs) under seated, simulated office-work conditions averaged 0.9 ± 0.3 million particles per person-h. Walking was associated with a 5-6× increase in the emission rate. During both walking and sitting, 60-70% or more of emissions originated from the floor. The increase in emissions during walking (vs. while sitting) was mainly attributable to release of particles from the floor; the associated increased vigor of upper body movements also contributed. Clothing, or its frictional interaction with human skin, was demonstrated to be a source of coarse particles, and especially of the highly fluorescent fraction. Emission rates of FBAPs previously reported for lecture classes were well bounded by the experimental results obtained in this chamber study. In both settings, the size distribution of occupant FBAP emissions had a dominant mode in the 3-5 µm diameter range.

Size-resolved fluorescent biological aerosol particle concentrations and occupant emissions in a university classroom.

UNLABELLED: This study is among the first to apply laser-induced fluorescence to characterize bioaerosols at high time and size resolution in an occupied, common-use indoor environment. Using an ultraviolet aerodynamic particle sizer, we characterized total and fluorescent biological aerosol particle (FBAP) levels (1-15 µm diameter) in a classroom, sampling with 5-min resolution continuously during eighteen occupied and eight unoccupied days distributed throughout a one-year period. A material-balance model was applied to quantify per-person FBAP emission rates as a function of particle size. Day-to-day and seasonal changes in FBAP number concentration (NF ) values in the classroom were small compared to the variability within a day that was attributable to variable levels of occupancy, occupant activities, and the operational state of the ventilation system. Occupancy conditions characteristic of lecture classes were associated with mean NF source strengths of 2 × 10(6) particles/h/person, and 9 × 10(4) particles per metabolic g CO2 . During transitions between lectures, occupant activity was more vigorous, and estimated mean, per-person NF emissions were 0.8 × 10(6) particles per transition. The observed classroom peak in FBAP size at 3-4 µm is similar to the peak in fluorescent and biological aerosols reported from several studies outdoors. PRACTICAL IMPLICATIONS: Coarse particles that exhibit fluorescence at characteristic wavelengths are considered to be proxies for biological particles. Recently developed instruments permit their detection and sizing in real time. In a mechanically ventilated classroom, emissions from human occupants were a strong determinant of coarse-mode fluorescent biological aerosol particle (FBAP) levels. Human FBAP emission rates were significant under quiet occupancy conditions and increased with activity level. Fluorescent particle emissions peaked at a diameter of 3­4 µm, which is the expected modal size of airborne particles with associated microbes. Human activity patterns, and associated coarse FBAP and total particle levels varied strongly on short timescales. Thus, the dynamic temporal behavior of aerosol concentrations must be considered when determining collection protocols for samples meant to be representative of average concentrations using time-integrated or 'snapshot' bioaerosol measurement techniques.

Pulmonary epithelial cell expression of GM-CSF corrects the alveolar proteinosis in GM-CSF-deficient mice.

Mutation of the granulocyte-macrophage colony-stimulating factor (GM-CSF) gene by homologous recombination caused alveolar proteinosis in mice. To further discern the role of GM-CSF in surfactant homeostasis, the synthesis of GM-CSF was directed to the respiratory epithelium of GM-CSF-hull mutant mice (GM-/-) with a chimeric gene expressing GM-CSF under the control of the promoter from the human surfactant protein-C (SP-C) gene. Transgenic mice bearing the SP-C-GM-CSF construct (SP-C-GM+) were bred to GM-/- mice resulting in complete correction of alveolar proteinosis in bitransgenic GM-/-, SP-C-GM+ mice. No effects of the transgene were found outside the lung. GM-CSF was increased in bronchoalveolar lavage fluid of the bitransgenic mice. Surfactant proteins-A and -B and phospholipid in bronchoalveolar lavage fluid were normalized in the GM-/-, SP-C-GM+ mice. SP-A, -B, and -C mRNAs were unaltered in lungs from GM-CSF-deficient and -replete mice. Expression of GM-CSF in respiratory epithelial cells of transgenic mice restores surfactant homeostasis in GM-/- mice. From these findings, we conclude that GM-CSF regulates the clearance or catabolism rather than synthesis of surfactant proteins and lipids.

Rainforest aerosols as biogenic nuclei of clouds and precipitation in the Amazon.

The Amazon is one of the few continental regions where atmospheric aerosol particles and their effects on climate are not dominated by anthropogenic sources. During the wet season, the ambient conditions approach those of the pristine pre-industrial era. We show that the fine submicrometer particles accounting for most cloud condensation nuclei are predominantly composed of secondary organic material formed by oxidation of gaseous biogenic precursors. Supermicrometer particles, which are relevant as ice nuclei, consist mostly of primary biological material directly released from rainforest biota. The Amazon Basin appears to be a biogeochemical reactor, in which the biosphere and atmospheric photochemistry produce nuclei for clouds and precipitation sustaining the hydrological cycle. The prevailing regime of aerosol-cloud interactions in this natural environment is distinctly different from polluted regions.

Chemically-resolved volatility measurements of organic aerosol fom different sources.

A newly modified fast temperature-stepping thermodenuder (TD) was coupled to a High Resolution Time-of-Flight Aerosol Mass Spectrometer for rapid determination of chemically resolved volatility of organic aerosols (OA) emitted from individual sources. The TD-AMS system was used to characterize primary OA (POA) from biomass burning, trash burning surrogates (paper and plastic), and meat cooking as well as chamber-generated secondary OA (SOA) from alpha-pinene and gasoline vapor. Almost all atmospheric models represent POA as nonvolatile, with no allowance for evaporation upon heating or dilution, or condensation upon cooling. Our results indicate that all OAs observed show semivolatile behavior and that most POAs characterized here were at least as volatile as SOA measured in urban environments. Biomass-burning OA (BBOA) exhibited a wide range of volatilities, but more often showed volatility similar to urban OA. Paper-burning resembles some types of BBOA because of its relatively high volatility and intermediate atomic oxygen-to-carbon (O/C) ratio, while meat-cooking OAs (MCOA) have consistently lower volatility than ambient OA. Chamber-generated SOA under the relatively high concentrations used intraditional experiments was significantly more volatile than urban SOA, challenging extrapolation of traditional laboratory volatility measurements to the atmosphere. Most OAs sampled show increasing O/C ratio and decreasing H/C (hydrogen-to-carbon) ratio with temperature, further indicating that more oxygenated OA components are typically less volatile. Future experiments should systematically explore a wider range of mass concentrations to more fully characterize the volatility distributions of these OAs.

Evolution of organic aerosols in the atmosphere.

Organic aerosol (OA) particles affect climate forcing and human health, but their sources and evolution remain poorly characterized. We present a unifying model framework describing the atmospheric evolution of OA that is constrained by high-time-resolution measurements of its composition, volatility, and oxidation state. OA and OA precursor gases evolve by becoming increasingly oxidized, less volatile, and more hygroscopic, leading to the formation of oxygenated organic aerosol (OOA), with concentrations comparable to those of sulfate aerosol throughout the Northern Hemisphere. Our model framework captures the dynamic aging behavior observed in both the atmosphere and laboratory: It can serve as a basis for improving parameterizations in regional and global models.

Structure and regulation of the murine Clara cell secretory protein gene.

Clara cell secretory protein (CC10 or CCSP) is an abundant component of airway secretions and has the ability to bind small hydrophobic molecules. Genomic clones were isolated for the murine gene coding for Clara cell secretory protein. Nucleotide sequence analysis revealed that the gene was composed of three exons that span 4316 bp. Organization of the murine CCSP gene was very similar to that of the rabbit gene that codes for the biochemically related uteroglobin protein. Messenger RNAs for both genes were coded for by three exons, counterparts of which encode similar structural and functional protein domains. Transcriptional regulatory elements in the 5' flanking DNA were conserved between species, as were the functional properties of these elements when characterized in assays of promoter function. These data support the notion that Clara cell secretory protein genes from the rat and mouse, and the uteroglobin gene in rabbit, represent interspecies homologues.

Cis-active elements controlling lung cell-specific expression of human pulmonary surfactant protein B gene.

Human surfactant protein B (SPB) is a 79-amino-acid hydrophobic protein that enhances the surface active properties of pulmonary surfactant. SPB is expressed in nonciliated bronchiolar and alveolar type II cells of the respiratory epithelium, and its expression increases markedly late in gestation. In the present study, a human pulmonary adenocarcinoma cell line, H441, was used in both functional and biochemical assays to identify DNA sequences controlling lung cell-specific expression of the SPB gene. DNase I hypersensitive studies demonstrated two distinct regions of lung cell-specific hypersensitivity located proximal to the SPB promoter and within the eighth intron of the gene. To functionally define these DNA sequences, a series of plasmid vectors were constructed in which segments of the human SPB gene and 5'-flanking sequence were linked to a CAT reporter gene and assayed for expression in lung and nonlung cell lines. Whereas far upstream and intronic sequences did not contain enhancer-like elements, a 259-base pair DNA segment (base pair -218 to +41) was sufficient to support lung cell-specific expression. DNase I footprinting demonstrated that this pulmonary epithelial cell-specific promoter fragment contained five nuclear protein-binding sites, two of which bound lung cell-specific nuclear protein complexes. These results suggest that the pulmonary epithelial cell-specific expression of SPB is determined, in part, by both ubiquitous and cell type-specific protein-DNA interactions within the proximal promoter region.

cis-acting elements that confer lung epithelial cell expression of the CC10 gene.

To define cis-acting genetic elements responsible for cell-specific transcriptional regulation of the CC10 gene, DNA sequences spanning nucleotides -2338 to +49 of the rat CC10 gene were linked to a reporter gene coding for chloramphenicol acetyltransferase (CAT). In transient expression assays, CC10 sequences were capable of restricting CAT expression to a human lung adenocarcinoma cell line similar to pulmonary Clara cells. Transgenic mice harboring the hybrid RtCC10-CAT construct expressed high levels of CAT activity specifically within protein extracts of lung and trachea. Transcripts for the CAT reporter gene colocalized with those for the endogenous murine CC10 gene within the airways of transgenic mice. Functional analysis of deletion mutants identified stimulatory, inhibitory, and cell type-specific transcriptional regulatory elements. The results of gel retention and DNaseI protection assays suggest that a transcriptional stimulatory region located between -320 and -175, and a cell type-specific regulatory element located between -175 and +49, result from a series of protein-DNA interactions occurring at -220 to -205 and -128 to -86, respectively. Lung epithelial specific transcriptional regulatory elements described herein will be useful for expression of chimeric genes within epithelial cells lining the trachea, bronchi, and bronchioles of mice.