Culturability and concentration of indoor and outdoor airborne fungi in six single-family homes

In this study, the culturability of indoor and outdoor airborne fungi was determined through long-term sampling (24-h) using a Button Personal Inhalable Aerosol Sampler. The air samples were collected during three seasons in six Cincinnati area homes that were free from moisture damage or visible mold. Cultivation and total microscopic enumeration methods were employed for the sample analysis. The geometric means of indoor and outdoor culturable fungal concentrations were 88 and 102 colony-forming units (CFU) m(-3), respectively, with a geometric mean of the I/O ratio equal to 0.66. Overall, 26 genera of culturable fungi were recovered from the indoor and outdoor samples. For total fungal spores, the indoor and outdoor geometric means were 211 and 605 spores m(-3), respectively, with a geometric mean of I/O ratio equal to 0.32. The identification revealed 37 fungal genera from indoor and outdoor samples based on the total spore analysis. Indoor and outdoor concentrations of culturable and total fungal spores showed significant correlations (r = 0.655, p<0.0001 and r = 0.633, p<0.0001, respectively). The indoor and outdoor median viabilities of fungi were 55% and 25%, respectively, which indicates that indoor environment provides more favorable survival conditions for the aerosolized fungi. Among the seasons, the highest indoor and outdoor culturability of fungi was observed in the fall. Cladosporium had a highest median value of culturability (38% and 33% for indoor and outdoor, respectively) followed by Aspergillus/Penicillium (9% and 2%) among predominant genera of fungi. Increased culturability of fungi inside the homes may have important implications because of the potential increase in the release of allergens from viable spores and pathogenicity of viable fungi on immunocompromised individuals.     

Review of PCBs in US schools: a brief history,an estimate of the number of impacted schools,and an approach for evaluating indoor air samples

PCBs in building materials such as caulks and sealants are a largely unrecognized source of contamination in the building environment. Schools are of particular interest, as the period of extensive school construction (about 1950 to 1980) coincides with the time of greatest use of PCBs as plasticizers in building materials. In the USA, we estimate that the number of schools with PCB in building caulk ranges from 12,960 to 25,920 based upon the number of schools built in the time of PCB use and the proportion of buildings found to contain PCB caulk and sealants. Field and laboratory studies have demonstrated that PCBs from both interior and exterior caulking can be the source of elevated PCB air concentrations in these buildings, at levels that exceed health-based PCB exposure guidelines for building occupants. Air sampling in buildings containing PCB caulk has shown that the airborne PCB concentrations can be highly variable, even in repeat samples collected within a room. Sampling and data analysis strategies that recognize this variability can provide the basis for informed decision making about compliance with health-based exposure limits, even in cases where small numbers of samples are taken. The health risks posed by PCB exposures, particularly among children, mandate precautionary approaches to managing PCBs in building materials.     

Concentrations and diversity of microbes from four local bioaerosol emission sources in Finland

Microbial particles can readily be released into the air from different types of man-made sources such as waste operations. Microbiological emissions from different biological sources and their dispersion may be an issue of concern for area planning and for nearby residents. This study was designed to determine the concentrations and diversity of microbiological emissions from four different man-made source environments: waste center with composting windrows, sewage treatment plant, farming environment, and cattle manure spreading. Samples of airborne particles were collected onto polyvinyl chloride filters at three distances along the prevailing downwind direction, from each source environment during a period of approximately 1 week. These samples were analyzed for 13 species or assay groups of fungi, bacterial genus Streptomyces, and Gram-positive and -negative bacteria using quantitative polymerase chain reaction (PCR). Samples for determining the concentrations of viable fungi and bacteria were collected from all environments using a six-stage impactor. The results show that there were variations in the microbial diversity between the source environments. Specifically, composting was a major source for the fungal genera Aspergillus and Penicillium, particularly for Aspergillus fumigatus, and for the bacterial genus Streptomyces. Although the microbial concentrations in the sewage treatment plant area were significantly higher than those at 50 or 200 m distance from the plant area, in the farming environment or cattle manure spreading area, no significant difference was observed between different distances from the source. In summary, elevated concentrations of microbes that differ from background can only be detected within a few hundred meters from the source. This finding, reported earlier for culturable bacteria and fungi, could thus be confirmed using molecular methods that cover both culturable and nonculturable microbial material.     

Size distributions of airborne microbes in moisture-damaged and reference school buildings of two construction types

Any risk assessment of moisture-damaged buildings requires an accurate characterization of the factors contributing to the human exposure. In this study, the size distributions of indoor air viable fungi and bacteria and average mean diameters of the most common fungi in school buildings were determined. One special focus was to analyze how the microbial size distributions are affected by the building frame (either wooden or concrete) and moisture damage in the building. The study was performed in 32 school buildings classified as moisture-damaged (index) and non-damaged (reference) schools according to technical building investigations. Sampling for indoor air microbes was carried out using a cascade impactor that collects particles on six stages (range from 0.65 to >7 μm) according to their aerodynamic diameters. Both wooden and concrete schools had their highest fungal levels in the size range of 1.1–4.7 μm. However, the concentrations of fungi in all size classes were higher in wooden schools than in concrete schools. Moisture damage-associated differences in size distribution, in the particle size range of 1.1–2.1 μm, were seen in concrete schools but not in wooden schools. In general, the average geometric mean diameter (d_g,ave) of total viable fungi was smaller in wooden schools than in concrete schools, and smaller in index schools of both construction types than in their reference schools. Variation in particle size, however, by genus was observed. No differences in particle size distributions of viable airborne bacteria were found. Our results on the dependency of the particle size on the building type and presence of moisture damage provide an interesting point to be considered in assessing the complex issue of indoor-related bioaerosol exposures.     

Fungi and bacteria in mould-damaged and non-damaged office environments in a subarctic climate

The fungi and bacterial levels of the indoor air environments of 77 office buildings were measured in winter and a comparison was made between the buildings with microbe sources in their structures and those without such sources. Penicillium, yeasts, Cladosporium and non-sporing isolates were the commonest fungi detected in the indoor air and in settled dust, in both the mould-damaged and control buildings. Aspergillus ochraceus, Aspergillus glaucus and Stachybotrys chartarium were found only in environmental samples from the mould-damaged buildings. Some other fungi, with growth requiring of water activity, a_w, above 0.85, occurred in both the reference and mould-damaged buildings, but such fungi were commoner in the latter type of buildings. The airborne concentrations of Penicillium, Aspergillus versicolor and yeasts were the best indicators of mould damage in the buildings studied. Penicillium species and A. versicolor were also the most abundant fungi in the material samples. This study showed that the fungi concentrations were very low (2–45 cfu m⁻³ 90% of the concentrations being <15 cfu m⁻³) in the indoor air of the normal office buildings. Although the concentration range of airborne fungi was wider for the mould-damaged buildings (2–2470 cfu m⁻³), only about 20% of the samples exceeded 100 cfu m⁻³. The concentrations of airborne bacteria ranged from 12 to 540 cfu m⁻³ in the control buildings and from 14 to 1550 cfu m⁻³ in the mould-damaged buildings. A statistical analysis of the results indicated that bacteria levels are generally <600 cfu m⁻³ in office buildings in winter and fungi levels are <50 cfu m⁻³. These normal levels are applicable to subarctic climates for urban, modern office buildings when measurements are made using a six-stage impactor. These levels should not be used in evaluations of health risks, but elevated levels may indicate the presence of abnormal microbe sources in indoor air and a need for additional environmental investigations.     

Volatile metabolites from indoor molds grown on media containing wood constituents

Since volatile mold metabolites are used for the detection of mold growth in buildings, it was interesting to determine whether different indoor mold species show different affinity for the major components of wood, a common building material. Growth and volatile metabolites were studied when Aspergillus versicolor, Penicillium chrysogenum, and P. palitans were grown on laboratory substrates containing the major wood constituents cellulose, xylan and lignin. Microbial volatile organic compounds (MVOCs) were characterized by thermal desorption/gas chromatography/mass spectroscopy. Growth and volatile metabolites varied considerably and there appeared to be complementary substrate specificities for P. chrysogenum, and P. palitans grown on cellulose and xylan. The failure of A. versicolor to produce characteristic MVOCs when grown on media containing wood constituents suggests that systems using volatile metabolites to detect microbial growth in buildings may be fundamentally unreliable for the detection of this species.     

Volatile metabolites from mold growth on building materials and synthetic media

Mold species which were isolated from damp buildings were grown on sterile building materials and some synthetic media in order to study the microbial volatile organic compounds produced. Patterns of the microbial volatile organic compounds (MVOC) were very media dependent but media which favor terpene biosynthesis may give patterns unique enough for identification of dominant indoor molds.     

Seasonal and diurnal variability in airborne mold from an indoor residential environment in northern New York

It is well known that characterization of airborne bioaerosols in indoor environments is a challenge because of inherent irregularity in concentrations, which are influenced by many environmental factors. The primary aim of this study was to quantify the day-to-day variability of airborne fungal levels in a single residential environment over multiple seasons. Indoor air quality practitioners must recognize the inherent variability in airborne bio-aerosol measurements during data analysis of mold investigations. Changes in airborne fungi due to varying season and day is important to recognize when considering health impacts of these contaminants and when establishing effective controls. Using an Andersen N6 impactor, indoor and outdoor bioaerosol samples were collected on malt extract agar plates for 18 weekdays and 19 weekdays in winter and summer, respectively. Interday and intraday variability for the bioaerosols were determined for each sampler. Average fungal concentrations were 26 times higher during the summer months. Day-to-day fungal samples showed a relatively high inconsistency suggesting airborne fungal levels are very episodic and are influenced by several environmental factors. Summer bio-aerosol variability ranged from 7 to 36% and winter variability from 24 to 212%; these should be incorporated into results of indoor mold investigations. The second objective was to observe the relationship between biological and nonbiological particulate matter (PM). No correlation was observed between biological and nonbiological PM. Six side-by-side particulate samplers collected coarse PM (PM10) and fine PM (PM2.5) levels in both seasons. PM2.5 particulate concentrations were found to be statistically higher during summer months. Interday variability observed during this study suggests that indoor air quality practitioners must adjust their exposure assessment strategies to reflect the temporal variability in bioaerosol concentrations.     

Concentrations and Diversity of Microbes from Four Local Bioaerosol Emission Sources in Finland

ABSTRACT

Microbial particles can readily be released into the air from different types of man-made sources such as waste operations. Microbiological emissions from different biological sources and their dispersion may be an issue of concern for area planning and for nearby residents. This study was designed to determine the concentrations and diversity of microbiological emissions from four different man-made source environments: waste center with composting windrows, sewage treatment plant, farming environment, and cattle manure spreading. Samples of airborne particles were collected onto polyvinyl chloride filters at three distances along the prevailing downwind direction, from each source environment during a period of approximately 1 week. These samples were analyzed for 13 species or assay groups of fungi, bacterial genus Streptomyces, and Gram-positive and -negative bacteria using quantitative polymerase chain reaction (PCR). Samples for determining the concentrations of viable fungi and bacteria were collected from all environments using a six-stage impactor. The results show that there were variations in the microbial diversity between the source environments. Specifically, composting was a major source for the fungal genera Aspergillus and Penicillium, particularly for Aspergillus fumigatus, and for the bacterial genus Streptomyces. Although the microbial concentrations in the sewage treatment plant area were significantly higher than those at 50 or 200 m distance from the plant area, in the farming environment or cattle manure spreading area, no significant difference was observed between different distances from the source. In summary, elevated concentrations of microbes that differ from background can only be detected within a few hundred meters from the source. This finding, reported earlier for culturable bacteria and fungi, could thus be confirmed using molecular methods that cover both culturable and nonculturable microbial material.

IMPLICATIONS Concentrations and diversity of airborne microbes increase due to particle emissions from different biological waste treatment applications. However, these emissions cannot be separated from the background concentrations after more than a few hundred meters from the source. As part of a risk assessment, it may be necessary to confirm the behavior of microbial emissions from a specific source. Quantitative PCR is a useful tool for estimating total concentrations of different microbial species or groups as it detects both culturable and nonculturable microbial material.     

Evaluating the capabilities of Aerosol-to-Liquid Particle Extraction System (ALPXS)/ICP-MS for monitoring trace metals in indoor air

This study investigates the application of the Aerosol-to-Liquid Particle Extraction System (ALPXS), which uses wet electrostatic precipitation to collect airborne particles, for multi-element indoor stationary monitoring. Optimum conditions are determined for capturing airborne particles for metal determination by inductively coupled plasma–mass spectrometry (ICP-MS), for measuring field blanks, and for calculating limits of detection (LOD) and quantification (LOQ). Due to the relatively high flow rate (300 L min^?1), a sampling duration of 1 hr to 2 hr was adequate to capture airborne particle-bound metals under the investigated experimental conditions. The performance of the ALPXS during a building renovation demonstrated signal-to-noise ratios appropriate for sampling airborne particles in environments with elevated metal concentrations, such as workplace settings. The ALPXS shows promise as a research tool for providing useful information on short-term variations (transient signals) and for trapping particles into aqueous solutions where needed for subsequent characterization. As the ALPXS does not provide size-specific samples, and its efficiency at different flow rates has yet to be quantified, the ALPXS would not replace standard filter-based protocols accepted for regulatory applications (e.g., exposure measurements), but rather would provide additional information if used in conjunction with filter based methods.

ImplicationsThis study investigates the capability of the Aerosol-to-Liquid Particle Extraction System (ALPXS) for stationary sampling of airborne metals in indoor workplace environments, with subsequent analysis by ICP-MS. The high flow rate (300 L/min) permits a short sampling duration (< 2 hr). Results indicated that the ALPXS was capable of monitoring short-term changes in metal emissions during a renovation activity. This portable instrument may prove to be advantageous in occupational settings as a qualitative indicator of elevated concentrations of airborne metals at short time scales.     

Effects of sawdust pollution on the germination of fungal spores in Lagos Lagoon

Four fungi, Aspergillus flavus, Aspergillus giganteus, Cladosporium oxysporum a and Trichoderma aureoviride, isolated from Lagos Lagoon, were tested for spore germination in aqueous sawdust extract of different hardwood species (Khaya ivorensis, Mitragyna ciliata and Triplochiton scleroxylon). Extracts of M. ciliata were inhibitory to spore germination especially at higher concentrations. Germ tubes of spores decreased in length with increase in extract concentration for C. oxysporum and T. aureoviride, while Aspergillus species showed increase in length up to a peak at 3% sawdust extract concentration, and thereafter germ tube lengths decreased with increasing concentration. Extracts of T. scleroxylon stimulated the spores and percentage germination increased at higher extract concentrations with no significant difference in germ tube length. Similarly, K. ivorensis had a stimulatory effect on spore germination and length of germ tube, especially at higher extract concentrations. Addition of soluble exogenous carbon and nitrogen sources to sawdust extract enhanced spore germination. Apart from A. flavus, which had only 9% germination, all the spores failed to germinate in lagoon water having 21% salinity. The spores were also inhibited by in lagoon water having 21 per thousand salinity. The spores were also inhibited by various inorganic salts, i.e. CaCl(2), KH(2)PO(4), MgSO(4) and NaCl, present in Lagos Lagoon. The results suggest that sawdust pollution causes enrichment of the lagoon, thereby enhancing spore germination.     

Fluorocarbons in the Los Angeles Basin

Ambient air concentrations of fluorocarbon 11 (fluorotrichloromethane) and fluoro-carbon 12 (dichlorodifluoromethane) have been measured using a gas chro-matograph equipped with a pulsed, electron capture detector. Air samples taken on a moderately smoggy day in July 1970, at several locations near Los Angeles gave average readings of fluorocarbon 12, 0.7 ppb and fluorocarbon 11, 0.56 ppb. These readings were contrasted with those taken in early February 1973 when the air was clear and marked with turbulence due to several seasonal rain storms. The readings of both fluorocarbon 1 1 and 12 averaged about 25% less during clear weather than those taken during moderate smog. The effects of weather conditions on the concentration were also dramatically pointed out by the February samples, in that as much as a tenfold change in concentrations of both fluorocarbons from location to location and from day to day at the same location was observed. A concentration versus altitude study clearly revealed that fluorocarbons are trapped by an inversion layer. Examination of air samples taken in the vicinity of factories known to be users of fairly large quantities of fluorocarbons revealed in part how large users contribute to the atmospheric concentrations of fluorocarbons. A comparison of fluorocarbon levels in homes and public buildings with ambient outside air levels revealed that the concentrations in some homes and buildings may be as much as several thousand times as high as levels in outside air. Inside the homes and public buildings, levels were as high as one-half of a part per million. Long term photolysis studies in simulated sunlight of both fluorocarbons 11 and 12 in ambient air samples and in air samples with 1 ppm of hydrocarbon and 1 ppm of nitrogen oxides revealed that the two fluorocarbons are photochemically stable even when photolyzed for several weeks.     

Influence of growth form on the accumulation of airborne copper by lichens

Lichens are known to accumulate airborne elements. This characteristic makes them useful as biomonitors of air quality. However, direct correlations of element concentrations in the air with element concentrations in lichen thalli are generally unavailable. The purpose of this study was to quantitatively examine the relationship between concentrations of copper in ambient air samples and thalli of foliose and fruticose lichens. Lichen samples from four sites along an air copper gradient were collected and analyzed. Foliose specimens consistently accumulated more than twice as much copper as fruticose specimens at all four sites. The relationship between copper concentrations in foliose and fruticose lichens and ambient air samples along an airborne copper gradient was examined using a stepwise regression model. An R² value of (0.84) and an F-statistic of (182.5, p<0.001) for the model indicate that variability in lichen copper concentrations between sites is explained by airborne copper concentrations. Based on the regression analysis both foliose and fruticose growth forms appear to accurately predict airborne copper concentrations. A significant interaction between the airborne copper and growth form variables and large differences in the calculated slopes suggests that foliose lichens more efficiently accumulate airborne copper than fruticose lichens.     

An analytical method for the measurement of nonviable bioaerosols.

Exposures from indoor environments are a major issue for evaluating total long-term personal exposures to the fine fraction (<2.5 microm in aerodynamic diameter) of particulate matter (PM). It is widely accepted in the indoor air quality (IAQ) research community that biocontamination is one of the important indoor air pollutants. Major indoor air biocontaminants include mold, bacteria, dust mites, and other antigens. Once the biocontaminants or their metabolites become airborne, IAQ could be significantly deteriorated. The airborne biocontaminants or their metabolites can induce irritational, allergic, infectious, and chemical responses in exposed individuals. Biocontaminants, such as some mold spores or pollen grains, because of their size and mass, settle rapidly within the indoor environment. Over time they may become nonviable and fragmented by the process of desiccation. Desiccated nonviable fragments of organisms are common and can be toxic or allergenic, depending upon the specific organism or organism component. Once these smaller and lighter fragments of biological PM become suspended in air, they have a greater tendency to stay suspended. Although some bioaerosols have been identified, few have been quantitatively studied for their prevalence within the total indoor PM with time, or for their affinity to penetrate indoors. This paper describes a preliminary research effort to develop a methodology for the measurement of nonviable biologically based PM, analyzing for mold and ragweed antigens and endotoxins. The research objectives include the development of a set of analytical methods and the comparison of impactor media and sample size, and the quantification of the relationship between outdoor and indoor levels of bioaerosols. Indoor and outdoor air samples were passed through an Andersen nonviable cascade impactor in which particles from 0.2 to 9.0 microm were collected and analyzed. The presence of mold, ragweed, and endotoxin was found in all eight size ranges. The presence of respirable particles of mold and pollen found in the fine particle size range from 0.2 to 5.25 microm is evidence of fragmentation of larger source particles that are known allergens.     

Dust build-up on surfaces in the indoor environment

The concentration and the composition of dust in the indoor environment has been associated with reported symptoms of the sick building syndrome. Levels of airborne concentrations of dust particles are well known. However, the relation to dust on surfaces for office environments are not well described. In this study, 662 measurements were performed of surface dust concentrations on hard surfaces in 19 buildings within Harvard University based on a sticking gelatine foil method. The measure is the dust covered area of the surface as a percentage. In three offices, the build-up of dust on surfaces was measured for a period of five days. Close to these surfaces the airborne PM_2.5 and PM₁₀ particle mass concentrations were measured simultanously. A significant correlation between the dust build-up and the difference between the PM₁₀ and the PM_2.5 was established. The particle size distribution was measured by means of an Aerodynamic Particle Sizer. The mean dust build-up normalized with the measured PM₁₀ was approximately four times higher than the equivalent calculated by a deposition model. This may in part be due to the effect of preferred orientation when particles settle to a surface. Different data for dust on surfaces and airborne particles in offices were compared. The levels of airborne particles in offices in Europe seem to be higher than the levels in the US.     

Performance of photocatalytic lamps on reduction of culturable airborne microorganism concentration

Reduction of viable airborne Staphylococcus epidermidis and Aspergillus niger spore concentrations using two types of photocatalytic fluorescent lamps under controlled environmental conditions (25 vs. 35 °C and 55 vs. 75% relative humidity) were investigated. Visible white-light and UVA black light were in-house spray-coated with TiO₂ and then compared with a commercially coated visible white-light for microbial concentration reduction. The white-light photocatalytic lamps reduced the concentration of culturable S. epidermidis up to 92% independent of temperature or humidity change, while the black light photocatalytic lamps completely inactivated the culturable bacteria at 25 °C, 55% relative humidity. Humidity seemed to alleviate UVA damage since better bacteria survival was found. For A. niger spores, rising humidity or temperature could lower their concentration or drop their culturabilities so that a difference between the natural decay and photocatalytic disinfection could not be distinguished. Reductions of total bacteria and total fungi concentrations using these lamps were also examined under uncontrolled environmental conditions in an office and a waste-storage room. It was found that photocatalytic lamps could reduce total culturable bacteria concentration from 9 to 97% and total culturable fungi concentration from 3 to 95% within irradiation time of 30-480 min, respectively. Insignificant difference in concentration reduction among these photocatalytic lamps was pronounced.     

Assessment of indoor air in Austrian apartments with and without visible mold growth

Fungal spores are transported across great distances in the outdoor air and are also regularly found indoors. Building conditions and behavior-related problems in apartments may lead to massive growth of mold within a very short period of time.The aim of this study was to evaluate whether the visible growth of mold indoors influences the concentration of fungal spores in the air as well as the variety of their species. Samples were collected from 66 households in Austria. For each sampling, the corresponding outdoor air was measured as reference value. The size of the visible mold growth was categorized in order to correlate the extent of mold growth with the concentration of airborne spores as well as the fungal genera. In order to determine fungal spore concentrations in the air, the one-stage MAS-100^® air sampler was used. Malt extract agar (MEA) and dichloran glycerol agar (DG18) plates were used as culture media. The total colony forming units (CFU) per m³ were determined. The fungi were identified from the isolated colonies.The results show that in apartments visibly affected by mold, the median values were significantly higher than those of apartments without visible mold growth. The extent of visible mold growth is significantly correlated with both concentration of fungal spores (p<0.001) as well as the predominance of Penicillium sp. and Aspergillus sp. (p<0.001) in indoor air. The total fungal concentration of Penicillium and Aspergillus in the air of apartments is recommended for assessing fungal exposure.     

Site Sampling and Treatability Studies for Demonstration of WasteChem’s Asphalt Encapsulation Technology Under EPA’s SITE Program

ABSTRACT

Exposures from indoor environments are a major issue for evaluating total long-term personal exposures to the fine fraction (<2.5μm in aerodynamic diameter) of particulate matter (PM). It is widely accepted in the indoor air quality (IAQ) research community that biocontamination is one of the important indoor air pollutants. Major indoor air biocontaminants include mold, bacteria, dust mites, and other antigens. Once the biocontaminants or their metabolites become airborne, IAQ could be significantly deteriorated. The airborne biocontaminants or their metabolites can induce irritational, allergic, infectious, and chemical responses in exposed individuals.

Biocontaminants, such as some mold spores or pollen grains, because of their size and mass, settle rapidly within the indoor environment. Over time they may become nonviable and fragmented by the process of desiccation. Desiccated nonviable fragments of organisms are common and can be toxic or allergenic, depending upon the specific organism or organism component. Once these smaller and lighter fragments of biological PM become suspended in air, they have a greater tendency to stay suspended. Although some bioaerosols have been identified, few have been quantitatively studied for their prevalence within the total indoor PM with time, or for their affinity to penetrate indoors.

This paper describes a preliminary research effort to develop a methodology for the measurement of nonvi-able biologically based PM, analyzing for mold and ragweed antigens and endotoxins. The research objectives include the development of a set of analytical methods and the comparison of impactor media and sample size, and the quantification of the relationship between outdoor and indoor levels of bioaerosols. Indoor and outdoor air samples were passed through an Andersen nonviable cascade impactor in which particles from 0.2 to 9.0 um were collected and analyzed. The presence of mold, ragweed, and endotoxin was found in all eight size ranges. The presence of respirable particles of mold and pollen found in the fine particle size range from 0.2 to 5.25 um is evidence of fragmentation of larger source particles that are known allergens.     

Characteristics of indoor aerosols in residential homes in urban locations: a case study in Singapore

As part of a major study to investigate the indoor air quality in residential houses in Singapore, intensive aerosol measurements were made in an apartment in a multistory building for several consecutive days in 2004. The purpose of this work was to identify the major indoor sources of fine airborne particles and to assess their impact on indoor air quality for a typical residential home in an urban area in a densely populated country. Particle number and mass concentrations were measured in three rooms of the home using a real-time particle counter and a low-volume particulate sampler, respectively. Particle number concentrations were found to be elevated on several occasions during the measurements. All of the events of elevated particle concentrations were linked to indoor activities based on house occupant log entries. This enabled identification of the indoor sources that contributed to indoor particle concentrations. Activities such as cooking elevated particle number concentrations < or =2.05 x 10(5) particles/cm3. The fine particles collected on Teflon filter substrates were analyzed for selected ions, trace elements, and metals, as well as elemental and organic carbon (OC) contents. To compare the quality of air between the indoors of the home and the outdoors, measurements were also made outside the home to obtain outdoor samples. The chemical composition of both outdoor and indoor particles was determined. Indoor/outdoor (I/O) ratios suggest that certain chemical constituents of indoor particles, such as chloride, sodium, aluminum, cobalt, copper, iron, manganese, titanium, vanadium, zinc, and elemental carbon, were derived through migration of outdoor particles (I/O <1 or - 1), whereas the levels of others, such as nitrite, nitrate, sulfate, ammonium, cadmium, chromium, nickel, lead, and OC, were largely influenced by the presence of indoor sources (I/O >1).     

Quality assured measurements of animal building emissions: odor concentrations

Standard protocols for sampling and measuring odor emissions from livestock buildings are needed to guide scientists, consultants, regulators, and policy-makers. A federally funded, multistate project has conducted field studies in six states to measure emissions of odor, coarse particulate matter (PM(10)), total suspended particulates, hydrogen sulfide, ammonia, and carbon dioxide from swine and poultry production buildings. The focus of this paper is on the intermittent measurement of odor concentrations at nearly identical pairs of buildings in each state and on protocols to minimize variations in these measurements. Air was collected from pig and poultry barns in small (10 L) Tedlar bags through a gas sampling system located in an instrument trailer housing gas and dust analyzers. The samples were analyzed within 30 hr by a dynamic dilution forced-choice olfactometer (a dilution apparatus). The olfactometers (AC'SCENT International Olfactometer, St. Croix Sensory, Inc.) used by all participating laboratories meet the olfactometry standards (American Society for Testing and Materials and European Committee for Standardization [CEN]) in the United States and Europe. Trained panelists (four to eight) at each laboratory measured odor concentrations (dilution to thresholds [DT]) from the bag samples. Odor emissions were calculated by multiplying odor concentration differences between inlet and outlet air by standardized (20 degrees C and 1 atm) building airflow rates.