Airborne fungi in low and high allergic prevalence child care centers

Fungi exposure has been linked to asthma and allergies among children. To determine the association between fungal exposure and wheeze and rhinitis symptoms, we examined concentrations of culturable indoor and outdoor fungi of various aerodynamic sizes in low and high allergic prevalence child care centers (CCCs) in Singapore. Environmental parameters were also performed for air temperature, relative humidity and ventilation rates, while information on CCC characteristics was collected via an inspection. Most commonly recovered fungi were Penicillium, Aspergillus, Geotrichum, Cladosporium and sterile mycelia with Geotrichum and sterile mycelia amounting to an average of 71.5% of the total airborne culturable fungi studied. Indoor and outdoor total culturable fungi concentrations and those in the size range of 1.1–3.3 μm were significantly higher in high allergic prevalence CCCs. When fungal types/genera were compared, indoor and outdoor Geotrichum and sterile mycelia of aerodynamic sizes 1.1–3.3 μm were found to be significantly elevated in high allergic prevalence CCCs. Indeed, average geometric mean diameters (D_{g, ave}) of indoor and outdoor culturable fungi were consistently smaller in CCCs with high prevalence of allergies than those with low prevalence. We found significant associations of higher fungal concentrations, especially those with smaller aerodynamic sizes in CCCs situated near parks. There were no differences in fungal levels between CCCs with respect to their dampness profile mainly due to high CCC ventilation rates. Since particle size is a factor that determines where a fungi particle deposits in the respiratory tract, this study provides useful information in the etiology of wheeze and rhinitis symptoms among the CCC attending children.     

Indoor and outdoor bioaerosol levels at recreation facilities, elementary schools, and homes

One major deficiency in linking environmental exposure to health effects is the current lack of data on environmental exposure. Therefore, to address this issue, the present study measured the bacterial and fungal concentrations in the indoor and outdoor air from two types of recreation facility (42 bars and 41 Internet cafes), 44 classrooms at 11 elementary schools, and 20 homes under uncontrolled environmental conditions during both summer and winter. No major environmental problems were reported at the four microenvironments being investigated during the entire study period. Bacteria and fungi were found in all the air samples, and the environmental occurrence of individual fungi was in the order of Cladosprium, Penicillium, Aspergillus, and Alternaria. The six parameters surveyed in the present study were all found to influence the indoor and outdoor bioaerosol levels: microenvironment type, sampling time in elementary school classrooms, agar type for measuring the fungal species, seasonal variation, facility location, and summer survey periods. The indoor and outdoor air concentrations of bacteria and fungi found in this study were comparable to those in other reports, with GM values for the total bacteria and total fungi between 10 and 10³ colony-forming units per cubic meter of air (CFU m⁻³). The fungal concentrations found at most of the indoor environments fell within the specified guidelines of the American Conference of Government Industrial Hygienists (ACGIH), between 100 and 1000 CFU m⁻³ for the total fungi. However, the indoor bioaerosol concentrations at most of the surveyed environments exceeded the Korean indoor bioaerosol guideline (800 CFU m⁻³). Consequently, the current findings suggest the need for reducing strategy for indoor microorganisms at the surveyed microenvironments.     

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.     

Effect of gaseous chlorine dioxide on indoor microbial contaminants

Traditional and modern techniques for bioaerosol enumeration were used to evaluate the relative efficiency of gaseous chlorine dioxide (ClO2) in reducing the indoor microbial contamination under field and laboratory conditions. The field study was performed in a highly microbially contaminated house, which had had an undetected roof leak for an extended period of time and exhibited large areas of visible microbial growth. Air concentrations of culturable fungi and bacteria, total fungi determined by microscopic count and polymerase chain reaction (PCR) assays, endotoxin, and (1 --> 3)-beta-D-glucan were determined before and after the house was tented and treated with ClO2. The laboratory study was designed to evaluate the efficiency of ClO2 treatment against known concentrations of spores of Aspergillus versicolor and Stachybotrys chartarum on filter paper (surrogate for surface treatment). These species are commonly found in damp indoor environments and were detected in the field study. Upon analysis of the environmental data from the treated house, it was found that the culturable bacteria and fungi as well as total count of fungi (as determined by microscopic count and PCR) were decreased at least 85% after the ClO2 application. However, microscopic analyses of tape samples collected from surfaces after treatment showed that the fungal structures were still present on surfaces. There was no statistically significant change in airborne endotoxin and (1 --> 3)-beta-D-glucan concentration in the field study. The laboratory study supported these results and showed a nonsignificant increase in the concentration of (1 --> 3)-beta-D-glucan after ClO2 treatment.     

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.     

Workplace exposure to bioaerosols in pet shops, pet clinics, and flower gardens

The present study evaluated exposure to bioaerosols at three different types of facilities (pet shops, pet clinics, and flower gardens) by measuring the bacterial, fungal and/or PM(10) concentrations in indoor and outdoor air. Regardless of the season, the total bacteria and total fungi were detected for all samples, whereas the fungal genera were not. The bioaerosol concentrations measured in the flower gardens were significantly higher than those of the pet shops and pet clinics. The mean microbial concentrations at the three types of facilities were close to or exceeded the Korean indoor bioaerosol guidelines (800 CFU m(-3)), thus suggesting the need for remedial action regarding indoor microorganisms, in order to reduce the exposure at the surveyed facilities. Another suggestion was that contrary to the airborne microbes, flower gardens are not an important microenvironment for PM(10) (particulate matter 10 microm in aerodynamic diameter) exposure. Two temporal characteristics (seasonal variation and the summer survey period) were important regarding exposure to airborne microbes, depending upon the type of facility surveyed, microbial or sample types, whereas the sampling time of the day was not. The microbial concentration ratio of indoor air to outdoor air depended upon the facility and season.     

Applicability of a modified MCE filter method with Button Inhalable Sampler for monitoring personal bioaerosol inhalation exposure

In this study, a “modified” mixed cellulose ester (MCE) filter culturing method (directly placing filter on agar plate for culturing without extraction) was investigated in enumerating airborne culturable bacterial and fungal aerosol concentration and diversity both in different environments. A Button Inhalable Sampler loaded with a MCE filter was operated at a flow rate of 5 L/min to collect indoor and outdoor air samples using different sampling times: 10, 20, and 30 min in three different time periods of the day. As a comparison, a BioStage impactor, regarded as the gold standard, was operated in parallel at a flow rate of 28.3 L/min for all tests. The air samples collected by the Button Inhalable Sampler were directly placed on agar plates for culturing, and those collected by the BioStage impactor were incubated directly at 26 °C. The colony forming units (CFUs) were manually counted and the culturable concentrations were calculated both for bacterial and fungal aerosols. The bacterial CFUs developed were further washed off and subjected to polymerase chain reaction–denaturing gradient gel electrophoresis (DGGE) for diversity analysis. For fungal CFUs, microscopy method was applied to studying the culturable fungal diversity obtained using different methods. Experimental results showed that the performance of two investigated methods varied with sampling environments and microbial types (culturable bacterial and fungal aerosols). For bacterial aerosol sampling, both methods were shown to perform equally well, and in contrast the “modified” MCE filter method was demonstrated to enumerate more culturable fungal aerosols than the BioStage impactor. In general, the microbial species richness (number of gel bands) was observed to increase with increasing collection time. For both methods, the DGGE gel patterns were observed to vary with sampling time and environment despite of similar number of gel bands. In addition, an increase in sampling time from 20 to 30 min was found not to substantially alter the species richness. Regardless of the sampling methods, more species richness was observed in the outdoor environment than the indoor environment. This study described a new personal bioaerosol exposure assessment protocol, and it was demonstrated applicable in monitoring the personal bioaerosol exposure in replace of an Andersen-type impactor.     

Indoor particulate matter in urban residences of Alexandria,Egypt

Indoor particulate matter samples were collected in 17 homes in an urban area in Alexandria during the summer season. During air measurement in all selected homes, parallel outdoor air samples were taken in the balconies of the domestic residences. It was found that the mean indoor PM_2.5 and PM₁₀ (particulate matter with an aerodynamic diameter ≤2.5 and ≤10 μm, respectively) concentrations were 53.5 ± 15.2 and 77.2 ± 15.1 µg/m³, respectively. The corresponding mean outdoor levels were 66.2 ± 16.5 and 123.8 ± 32.1 µg/m³, respectively. PM_2.5 concentrations accounted, on average, for 68.8 ± 12.8% of the total PM₁₀ concentrations indoors, whereas PM_2.5 contributed to 53.7 ± 4.9% of the total outdoor PM₁₀ concentrations. The median indoor/outdoor mass concentration (I/O) ratios were 0.81 (range: 0.43–1.45) and 0.65 (range: 0.4–1.07) for PM_2.5 and PM₁₀, respectively. Only four homes were found with I/O ratios above 1, indicating significant contribution from indoor sources. Poor correlation was seen between the indoor PM₁₀ and PM_2.5 levels and the corresponding outdoor concentrations. PM₁₀ levels were significantly correlated with PM_2.5 loadings indoors and outdoors and this might be related to PM₁₀ and PM_2.5 originating from similar particulate matter emission sources. Smoking, cooking using gas stoves, and cleaning were the major indoor sources contributed to elevated indoor levels of PM₁₀ and PM_2.5.

Implications: The current study presents results of the first PM_2.5 and PM₁₀ study in homes located in the city of Alexandria, Egypt. Scarce data are available on indoor air quality in Egypt. Poor correlation was seen between the indoor and outdoor particulate matter concentrations. Indoor sources such as smoking, cooking, and cleaning were found to be the major contributors to elevated indoor levels of PM₁₀ and PM_2.5.     

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.     

Filtration of Radioactive Aerosols By Glass Fibers

Abstract

An ozone (O₃) exposure assessment study was conducted in Toronto, Ontario, Canada during the winter and summer of 1992. A new passive O₃ sampler developed by Harvard was used to measure indoor, outdoor, and personal O₃ concentrations. Measurements were taken weekly and daily during the winter and summer, respectively. Indoor samples were collected at a total of 50 homes and workplaces of study participants. Outdoor O₃ concentrations were measured both at home sites using the passive sampler and at 20 ambient monitoring sites with continuous monitors. Personal O₃ measurements were collected from 123 participants, who also completed detailed time-activity diaries. A total of 2,274 O₃ samples were collected. In addition, weekly air exchange rates of homes were measured.

This study demonstrates the performance of our O₃ sampler for exposure assessment. The data obtained are further used to examine the relationships between personal, indoor (home and workplace), and outdoor O₃ concentrations, and to investigate outdoor and indoor spatial variations in O₃ concentrations. Based on home outdoor and indoor, workplace, and ambient O₃ concentrations measured at the Ontario Ministry of the Environment (MOE) sites, the traditional microenvironmental model predicts 72% of the variability in measured personal exposures. An alternative personal O₃ exposure model based on outdoor measurements and time-activity information is able to predict the mean personal exposures in a large population, with the highest R² value of 0.41.     

Characteristics of microbial aerosols released from chicken and swine feces

Bioaerosols generated during livestock and poultry production are significant occupational hazards. This study investigates the characteristics of bioaerosols released from animal feces. Fresh feces from pigs and chickens were obtained and tested in a controlled-environment facility. Airborne viable (culturable) bacteria and fungi were sampled hourly for 48 hr. The predominant species were identified via polymerase chain reaction analysis. The number of bacterial colonies released from chicken feces increased gradually, peaked at approximately 20 hr, and remained relatively constant to test end; however, the bacterial colonies released from swine feces did not increase significantly. The chicken feces released significantly (P < 0.05) more bacterial aerosols than swine feces over 40 hr, by approximately 1 order of magnitude. However, the difference in total fungal aerosols released from the two feces types was relatively small (30-40%) and insignificant (P > 0.05). Aerosols sized between approximately 0.65 and 1.1 microm were predominant for bacteria, whereas aerosols sized between approximately 2.1 and 3.3 microm prevailed for fungi. Genera Stenotrophomonas were the predominant bacterial aerosols, whereas Cladosporium and Acremonium accounted for the greatest amounts of fungi from chicken and swine feces, respectively. More than 1000 culturable bacterial colonies can be released from 1 g of chicken feces per hour, and approximately 80% of these bioaerosols are respirable. Most bacterial aerosols released from swine and chicken feces were opportunistic human pathogens; thus, the significance of their presence warrants further investigations.     

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.     

Relationships between indoor and outdoor air pollution by carcinogenic PAHs and PCBs

PAHs and PCBs were collected simultaneously indoors and outdoors at eight non-smoking homes located in four buildings in high-traffic areas of Rome. The purpose was to evaluate the relevance of indoor air in contributing to the overall exposure of the urban population. The vertical distribution was also investigated by collecting outdoor samples at both road and roof level, and indoor samples in both a high and a low floor flat of each building. At one coal-heated building, samples were collected during both the heating and the non-heating season. No evident PAH source was present indoors. Indoor and outdoor daily concentrations of benzo[a]pyrene (BaP) ranged, respectively, 0.1–4.6 ng m⁻³ and 0.7–2.3 ng m⁻³. With the heating on, indoor PAH concentrations equalled or exceeded those outdoors, with BaP indoor/outdoor ratios up to 4; during the warm season, ratios decreased to 0.2–0.6. Indoor PAHs at the low floors exceeded the high-floor ones when the heating was off (vehicle exhausts being the dominant source), while being equal or lower with the heating on; the vertical gradient of indoor PAHs between different floors was within a factor of 2. Outdoor PAHs at roof level were 20–70% of those at road level, which in turn exceeded those at the medium-traffic station up to a factor of 4. The outdoor concentrations of Σ6 indicator PCBs ranged 0.1–1.6 ng m⁻³. Indoor PCB concentrations exceeded those outdoors by an approximate factor of 2–50. No vertical gradient was observed. The results indicated that indoor air may contribute to the overall exposure to PAHs and PCBs more than the urban air. They were also consistent with recent findings suggesting that indoor air can be a relevant source of PCBs for outdoor air.     

Dechlorane plus (DP) in indoor and outdoor air of an urban city in South China: Implications for sources and human inhalation exposure

Dechlorane Plus (DP) is a chemical of emerging concern due to the restrictions on brominated flame retardant formulations. However, very little information is known about the occurrence of DP in indoor and outdoor air and its associated health risk to the exposed human population. In this study, we examined the concentrations and isomer profiles of DP in archived air samples collected from 14 homes, 6 offices, and 10 public microenvironments in Guangzhou, China in 2004–2005. The average (median) value of atmospheric ΣDP (sum of anti-DP and syn-DP) concentration in the three indoor air was 5.73 ± 5.33 (3.62) for offices, 8.08 ± 5.17 (6.87) for homes, and 57.27 ± 83.08 (32.58) pg/m³ for public microenvironments, respectively. ΣDP concentration was significantly higher in the public microenvironments than those in homes and offices. The arithmetic mean and median concentrations of ΣDP in outdoor air were 36.00 and 28.76 pg/m³, respectively. Spatially and temporally consistent indoor and outdoor samples comparison suggested that outdoor air might be a relevant source of DP for indoor air. Average anti-DP fractional abundance (f_anti = 0.65 ± 0.04) in all outdoor samples was similar to those reported in other studies and indistinguishable from that of the commercial mixture (f_anti = 0.65). In contrast, a relatively large variation of f_anti values was found in the indoor samples, suggesting a complex degradation process of DP existing in these microenvironments. The calculated average daily doses of ΣDP were in the range of 0.38–2.21 ng/day for people intake through air inhalation, which was in the same order of magnitude compared with other exposure pathways for the general publics.     

VOC concentrations measured in personal samples and residential indoor,outdoor and workplace microenvironments in EXPOLIS-Helsinki,Finland

Thirty target volatile organic compounds (VOC) were analyzed in personal 48-h exposure samples and residential indoor, residential outdoor and workplace indoor microenvironment samples as a component of EXPOLIS-Helsinki, Finland. Geometric mean residential indoor concentrations were higher than geometric mean residential outdoor concentrations for all target compounds except hexane, which was detected in 40% of residential outdoor samples and 11% of residential indoor samples, respectively. Geometric mean residential indoor concentrations were significantly higher than personal exposure concentrations, which in turn were significantly higher than workplace concentrations for compounds that had strong residential indoor sources (d-limonene, alpha pinene, 3-carene, hexanal, 2-methyl-1-propanol and 1-butanol). 40% of participants in EXPOLIS-Helsinki reported personal exposure to environmental tobacco smoke (ETS). Participants in Helsinki that were exposed to ETS at any time during the 48-h sampling period had significantly higher personal exposures to benzene, toluene, styrene, m,p-xylene, o-xylene, ethylbenzene and trimethylbenzene. Geometric mean ETS-free workplace concentrations were higher than ETS-free personal exposure concentrations for styrene, hexane and cyclohexane. Geometric mean personal exposures of participants not exposed to ETS were approximately equivalent to time weighted ETS-free indoor and workplace concentrations, except for octanal and compounds associated with traffic, which showed higher geometric mean personal exposure concentrations than any microenvironment (o-xylene, ethylbenzene,benzene, undecane, nonane, decane, m,p-xylene, and trimethylbenzene). Considerable differences in personal exposure concentrations and residential levels of compounds with mainly indoor sources suggested differences in product types or the frequency of product use between Helsinki, Germany and the United States.     

Outdoor and indoor factors influencing particulate matter and carbon dioxide levels in naturally ventilated urban homes

ABSTRACT

The present study investigated indoor and outdoor concentrations of two particulate matter size fractions (PM₁₀ and PM_2.5) and CO₂ in 20 urban homes ventilated naturally and located in one congested residential and commercial area in the city of Alexandria, Egypt. The results indicate that the daily mean PM_2.5 concentrations measured in the ambient air, living rooms, and kitchens of all sampling sites exceeded the WHO guideline by 100%, 65%, and 95%, respectively. The daily mean outdoor and indoor PM₁₀ levels in all sampling sites were found to exceed the WHO guideline by 100% and 80%, respectively. The indoor PM₁₀ and PM_2.5 concentrations were significantly correlated with their corresponding outdoor levels, as natural ventilation through opening doors and windows allowed direct transfer of outdoor airborne particles into the indoor air. Most of the kitchens investigated had higher indoor concentrations of PM_2.5 and CO₂ than in living rooms. The elevated levels of PM_2.5 and CO₂ in domestic kitchens were probably related to inadequate ventilation. The current study attempted to understand the sources and the various indoor and outdoor factors that affect indoor PM₁₀, PM_2.5 and CO₂ concentrations. Several domestic activities, such as smoking, cooking, and cleaning, were found to constitute important sources of indoor air pollution. The indoor pollution caused by PM_2.5 was also found to be more serious in the domestic kitchens than in the living rooms and the results suggest that exposure to PM_2.5 is high and highlights the need for more effective control measures.

Implications: Indoor air pollution is a complex problem that involves many determinant factors. Understanding the relationships and the influence of various indoor and outdoor factors on indoor air quality is very important to prioritize control measures and mitigation action plans. There is currently a lack of research studies in Egypt to investigate determinant factors controlling indoor air quality for urban homes. The present study characterizes the indoor and outdoor concentrations of PM₁₀, PM_2.5, and CO₂ in residential buildings in Alexandria city. The study also determines the indoor and outdoor factors which influence the indoor PM and CO₂ concentrations as well as it evaluates the potential indoor sources in the selected homes. This research will help in the development of future indoor air quality standards for Egypt.     

Investigation of PM2.5 and carbon dioxide levels in urban homes

PM_2.5 (particulate matter with an aerodynamic diameter <2.5 μm) samples were collected in the indoor environments of 15 urban homes and their adjacent outdoor environments in Alexandria, Egypt, during the spring time. Indoor and outdoor carbon dioxide (CO₂) levels were also measured concurrently. The results showed that indoor and outdoor PM_2.5 concentrations in the 15 sites, with daily averages of 45.5 ± 11.1 and 47.3 ± 12.9 µg/m³, respectively, were significantly higher than the ambient 24-hr PM_2.5 standard of 35 µg/m³ recommended by the U.S. Environmental Protection Agency (EPA). The indoor PM_2.5 and CO₂ levels were correlated with the corresponding outdoor levels, demonstrating that outdoor convection and infiltration could lead to direct transportation indoors. Ventilation rates were also measured in the selected residences and ranged from 1.6 to 4.5 hr^?1 with median value of 3.3 hr^?1. The indoor/outdoor (I/O) ratios of the monitored homes varied from 0.73 to 1.65 with average value of 0.99 ± 0.26 for PM_2.5, whereas those for CO₂ ranged from 1.13 to 1.66 with average value of 1.41 ± 0.15. Indoor sources and personal activities, including smoking and cooking, were found to significantly influence indoor levels.

Implications: Few studies on indoor air quality were carried out in Egypt, and the scarce data resulted from such studies do not allow accurate assessment of the current situation to take necessary preventive actions. The current research investigates indoor levels of PM_2.5 and CO₂ in a number of homes located in the city of Alexandria as well as the potential contribution from both indoor and outdoor sources. The study draws attention of policymakers to the importance of the establishment of national indoor air quality standards to protect human health and control air pollution in different indoor environments.     

Winter indoor air pollution in Alaska: identifying a myth

The benzene and toluene levels inside three homes with attached garages were measured for 12 consecutive weeks during the winter months in Fairbanks, Alaska (Latitude 64.5 degrees N). Results for air samples collected over 12 h for the homes showed indoor benzene mixing ratios ranging from 1.6 to 20.4 parts per billion of mixing ratio volume (ppbv), and toluene air mixing ratios ranging from 7.3 to 41.6 ppbv. A correlation between benzene and toluene levels in each home and similar regression lines suggested the same major emission source, car and small equipment gasoline, present in attached garages. In one home, there was a correlation between indoor benzene mixing ratios and the urinary biomarker, trans,trans-muconic acid. Inside, air mixing ratios of benzene and toluene decreased with decreasing outside temperature in all homes studied, even though homes were relatively tight to prevent heat loss during this period of low winter outdoor temperatures. It is suggested that buildup of these pollutants indoors is prevented by the influence of an increased indoor/outdoor temperature differential and an ensuing increase in home ventilation.     

Distribution,sources and pollution status of Pb in indoor and outdoor dusts of Kerman City,SE Iran

The aims of this study were to explore the status of pollution and the temporal/spatial distribution of indoor and outdoor dust-Pb in the city of Kerman (SE Iran), located in a dry playa and arid climatic zone. Flat panes were laid at appropriate locations, in the indoor and the outdoor spaces of selected one-story houses in different areas of the city, to collect dust samples. Forty-two samples were taken and analyzed using the ICP-MS method. The measurements have shown that the outdoor dust-Pb concentrations varied from 23.7 to 275.2?mg kg^?1, with a mean value of 71.8?mg kg^?1, and indoor dust-Pb concentrations ranged from 47.6 to 150.2?mg kg^?1, with a mean value of 89.6?mg kg^?1. Based on these measurements, Pb was enriched in the outdoor and the indoor dust samples up to 48.8 and 29.4 times, respectively. Dilution, as a result of prevalence of geogenic dust in the outdoor space, is expected to be the main cause of the temporal differences. This study has shown that the eastern part of the city is more polluted compared to the other parts, and, because of the stable air conditions, the concentration of Pb in the summer dust is higher than the other seasons.     

An assessment of indoor air quality in recent Mexican immigrant housing in Commerce City, Colorado

An indoor air quality assessment was conducted on 100 homes of recent Mexican immigrants in Commerce City, Colorado, an urban industrial community north of Denver. Head of households were administered a family health survey, filled out an activity diary, and participated in a home inspection. Carbon monoxide (CO) and carbon dioxide (CO₂) were measured for 24 h inside the main living area and outside of the homes. Harvard Impactors were used to collect 24-h samples of PM_2.5 at the same locations for gravimetric analysis. Dust samples were collected by vacuuming carpeting and flooring at four locations within the home and analyzed by ELISA for seven allergens. Mean indoor and outdoor PM_2.5 levels were 27.2 and 8.5 μg m⁻³, respectively. Indoor PM_2.5 and CO₂ were elevated in homes for which the number of hours with door/window open was zero compared to homes in which the number of hours was high (>15 h). Indoor PM_2.5 levels did not correlate with outdoor levels and tended to increase with number of inhabitants, and results indicate that the source of indoor particles were occupants and their activities, excluding smoking and cooking. Mean indoor CO₂ and CO levels were 1170 and 2.4 ppm, respectively. Carbon monoxide was higher than the 24-h National Ambient Air Quality Standard in 3 of the homes. The predominant allergens were cat (Fel d 1) and mouse (Mus m 1) allergens, found in 20 and 34 homes, respectively.