Outdoor Airborne Research Articles

Levels of Indoor Airborne Microbes Associated with Ventilation Efficiency in Naturally-Ventilated Residences

Indoor microbial exposure has been implicated in various adverse health effects. This study aimed to examine the effects of ventilation efficiency on indoor/outdoor (I/O) levels of airborne microbes in homes with natural ventilation, a predominant type adopted by most residential buildings in Taiwan where high microbial concentrations have been reported. Environmental investigations were conducted in 44 homes. Indoor and outdoor airborne bacteria and fungi were collected using a Burkard sampler with Trypticase Soy agar and Malt Extract agar in a flow rate of 10 L/min. Air change rate (AC/H) was measured using the tracer gas concentration decay method. Indoor airborne bacteria and total fungi levels in most investigated houses were generally greater than 1000 CFU/m3. The most frequently isolated fungal genera were Aspergillus, Penicillium, Cladosporium, Alternaria and Yeast. Only the I/O ratios of A. niger and Penicillium were significantly higher for those homes with an air change rate of less than 2.13/h, the median value, compared to those with greater than 2.13 (p<0.05). A weak, but not significant, association was observed between the increasing I/O ratios of Cladosporium and Alternaria and increasing ACH rates. Such an association, however, could not be identified with concentrations of indoor and outdoor airborne bacteria. Results also suggested higher air change rate in residences with natural ventilation may, in turn, elevate effectively indoor microbial levels of outdoor origin for there may be absence of proper filtration.

Relationship between indoor and outdoor airborne fungal spores, pollen, and (1→3)-β-D-glucan in homes without visible mold growth

In this exploratory study, indoor and outdoor airborne fungal spores, pollen, and (1→3)-β-D-glucan levels were determined through long-term sampling (24-h) using a Button Personal Inhalable Aerosol Sampler. The air samples were collected in five Cincinnati area homes that had no visible mold growth. The total count of fungal spores and pollen in the collected samples was conducted under the microscope and Limulus Amebocyte Lysate (LAL) chromogenic assay method was utilized for the determination of the (1→3)-β-D-glucan concentration. For the combined number concentration of fungal spores and pollen, the indoor and outdoor geometric mean values were 573 and 6,435 m−3, respectively, with a geometric mean of the Indoor/Outdoor (I/O) ratio of .09. The geometric means of indoor and outdoor (1→3)-β-D-glucan concentrations were .92 and 6.44 ng m−3, respectively, with a geometric mean of the I/O ratio equal to .14. The I/O ratio of (1→3)-β-D-glucan concentration was found to be marginally greater than that calculated based on the combined number concentration of fungal spores and pollen. This suggests that (1→3)-β-D-glucan data are affected not only by intact spores and pollen grains but also by the airborne fragments of fungi, pollen, and plant material, which are ignored by traditional enumeration methodologies. Since the (1→3)-β-D-glucan level may elucidate the total exposure to fungal spores, pollen, and fungal fragments, its I/O ratio may be used as a risk marker for mold and pollen exposure in indoor environments.

Preliminary survey of indoor and outdoor airborne microfungi at coastal buildings in Egypt

Forty six species and two sterile fungi and yeast species were isolated from samples collected both indoors and outdoors of coastal buildings located in an Egyptian coastal city. Twenty flats from ten buildings were investigated; children living in these buildings have been reported to suffer from respiratory illnesses. Samples were taken using a New Brunswick sampler (model STA-101) operating for 3.0 min at a flow rate of 6.0 l/min. Most of the species isolated have been associated with symptoms of respiratory allergies. Indoors the total culturable fungal count was 1548 CFU/m3; outdoors, it was 1452 CFU/m3. Indoor values of culturable fungal count, total spores count and ergosterol content ranged from 52 to 124 CFU/m3, 100 to 400 spore/m3 and 5 to 27.7 mg/m3, respectively, whereas outdoor levels typically varied between 25 and 222 CFU/m3, 110 and 900 spore/m3 and 3.3 and 67.2 mg/m3, respectively. The maxima for these parameters were detected indoors in house no. 6 and outdoors, outside of house no. 7. The most abundant species were primarily mitosporic (2832 CFU/m3). The most frequent species in both the indoor and outdoor samples were Cladosporium cladosporioides followed by Alternaria alternata and Penicillium chrysogenum,with inside:outside ratios of 1.4, 1.8 and 1.9, respectively. The patterns of fungal abundance were influenced to some extent by changes in the relative humidity and temperature. Other factors, such as type of culture media, rate of sedimentation, size, survival rates of spore and species competition,also affected fungal counts and should be taken into consideration during any analysis of bioaerosol data.

Particle size distributions and concentrations of airborne endotoxin using novel collection methods in homes during the winter and summer seasons

A comparison study of novel collection methods for airborne bacteria and endotoxin was performed in an environmentally controlled chamber and in pilot-field studies. Airborne particulate matter was collected in swirling liquid impingers, air-monitoring filter cassettes, and with a micro-orifice uniform deposit impactor (MOUDI) to evaluate aerodynamic particle size distributions. Environmentally controlled chamber studies showed that impingers and MOUDI recovered significantly more airborne bacteria than filter cassettes, whereas collection methods for airborne endotoxin were not significantly different. In addition, total airborne bacteria and endotoxin concentrations were measured indoors and outdoors at three homes in Boulder, CO during winter and summer seasons. Indoor concentrations collected with the three different samplers were significantly different for airborne endotoxin, but not for airborne bacteria. Total airborne bacteria indoors and outdoors significantly varied with seasons. Outdoor airborne endotoxin significantly varied with season; no seasonal variation was seen for indoor airborne endotoxin. Indoor and outdoor levels were not significantly different for both airborne bacteria and endotoxin. The largest proportion of endotoxin was associated with airborne particulate matter <1 microm. This study compared sampling methods for airborne endotoxin, a potent and nonspecific immune system stimulant which can induce negative health responses. The data from this study showed that swirling liquid impingers and the micro-orifice uniform deposit impactor (MOUDI) recovered significantly more airborne endotoxin than the more widely adapted method of collecting airborne endotoxin on membrane filters, when collection methods were applied in realistic settings (homes). The MOUDI measured the particle size distribution of airborne endotoxin, which can be useful for determining endotoxin respiratory toxicity and its health effects.

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.

Exposure to airborne fungi and bacteria while commuting in passenger cars and public buses

The present study examined airborne microbe levels inside and outside passenger cars and public buses during two seasons (winter and summer). The prevalence level of individual fungal genera depended on the fungi and agar type, whereas a constant higher prevalence (>90%) was found for the total bacteria and total fungi. The four most prevalent fungal genera were Cladosporium, Penicillium, Aspergillus, and Alternaria in a descending order. The major parameters associated with the airborne microbe measurements included agar type, vehicle type, and seasonal variation. When compared to the malt extract agar (MEA), the dichloran glycerol 18 agar (DG-18) was found to produce better counts for the target fungi. The summer in-vehicle bacterial concentrations were significantly higher for public buses than for the passenger cars, whereas the reverse was true for summer in-vehicle total fungal concentrations. This pattern was also consistent with summer outdoor results. In contrast, the winter in-vehicle and outdoor airborne microbe levels were similar for cars and buses. Meanwhile, summer was generally found to have higher in-vehicle fungal concentrations than winter. The current in-vehicle airborne microbe concentrations were found to be similar to residential indoor values from other reports, such as bacterial values between 10 and 10 3 CFU m −3 and total fungal aerosol concentrations ranging from 10 to 10 3 CFU m −3. It was suggested that motor vehicles in which many individuals spend a certain percentage of their day or week for travel are also a potential microenvironment for individual exposure to airborne microbes.

ASSESSMENT OF MICROBIAL (B ACTERIA) CONCENTRATIONS OF AMBIENT AIR AT SEMI-ARID URBAN REGION: INFLUENCE OF METEOROLOGICAL FACTORS

In the present study, outdoor airborne microflora (bacteria) at different locations, viz; institutional, health care, commercial, traffic, industrial and agricultural areas of Tirupati  a semi-arid urban region, southern peninsular India was investigated during winter season, 2004. Concentrations of airborne viable bacteria averaged between 19 ± 5 CFU/m 3 (IE) and 3 ± 5 CFU/m 3 (SVU) and observed the following trend among the locations: IE > TG > CBS > TUDA > RUYA > SVU. Airborne Gram- positive bacteria were most abundant, with more than 60 to 90% of the measured population at each location. Developed regression models have been explained about 50% (or greater) variation in bacteria concentration at each location (except RUYA), due to the effect of meteorological factors - temperature, RH, and wind speed. Among these factors, wind speed had the most pronounced influence on bacterial concentration, with the regression coefficient (β) varied between 0.225 and 2.092, followed by the temperature. The overall air quality index (ABQI) with respect to bacterial composition of aerosol is found to be 22.33 which signifies that the quality of air is good. The results reveal that the airborne bacteria are contributed from terrestrial (soil) sources greatly followed by the little contribution from point sources. Keywords. Bioaerosol, airborne bacteria, meteorological factors, multiple linear regression, quality index, India.

Survey of Food and Airborne Allergen-specific IgE Levels in a General Population of 3-year-old Japanese Children

Background data on the allergic constitutions of a general population of Japanese children may provide important information regarding environmental factors that contribute to the increased incidence of allergic diseases and suggest clues for their prevention. Serum samples were obtained from a general population of 3-year-old children (612 samples) in the Kanto area and Asahikawa city. The serum levels of total and specific IgE antibodies against food allergens (egg white, milk, soybean, wheat), indoor airborne allergens (house dust, mite, cat dandruff), and outdoor airborne allergens (Japanese cedar or white birch pollen allergens) were determined and analyzed, along with the results of a questionnaire regarding medical history, and allergy-related subjective symptoms. The mean total IgE level of all subjects was 34.7 IU/ml, while that for the Kanto and Asahikawa areas was 44.7 and 22.5 IU/ml, respectively. Twenty six percent of the 612 children were judged positive for indoor airborne allergen-specific IgE, and 6.7% were positive for food allergen-specific IgE. Cedar allergen-specific IgE was detected in 15.6% of the children living in the Kanto area. The total IgE level was strongly correlated with the number of allergens to which the child was sensitized. A relatively large number (28.4%) of 3-year-old children possessed allergen-specific IgE antibodies. The basic data obtained in the general population in these two areas of Japan will be valuable for further evaluations of environmental influences on allergic disease.

Field study on changes in viability of airborne fungal propagules exposed to UV radiation.

The responses of airborne fungi to UV-B under natural conditions were investigated at the coastal station in Preila, Lithuania. Results of this investigation demonstrated that solar radiation has a marked lethal effect on outdoor airborne fungi. Sensitivity to solar radiation was the highest for the fungal propagules collected late in the evening (relative recovery 6.2%) and early morning (25.3%). The lowest sensitivity to solar radiation was observed for fungal propagules collected at midday (50.0%) and in the afternoon (53.0%). The reason for the lethal effect is thought to be elimination of the sensitive fraction of the night-time fungal populations as solar radiation gradually increases beginning at dawn. Among 356 fungus strains isolated during the investigations, 128 can be characterized as potential pathogens, and 21 strains among those most common in fungal populations belonging to plant, animal, and human pathogen groups. The collected fungal populations were exposed to solar UV-B irradiation for 2 h (from 12 p.m. to 2 p.m.). Fungal communities in the air samples were composed of saprotrophs, some of which are regarded as potential phytopathogens (Alternaria, Cladosporium, and Fusarium) or as entomopathogens (Beauveria, Paecilomyces, and Metarhizium). The airborne fungal species identified after exposure to solar radiation were predominantly: Aspergillus niger, Alternaria alternata, Cladosporium cladosporioides, Arthrinium phaerosporum, and dematiaceous sterile mycelium.

Indoor air quality investigation at air-conditioned and non-air-conditioned markets in Hong Kong

To characterize indoor air quality at the markets in Hong Kong, three non-air-conditioned and two air-conditioned markets were selected for this study. The indoor air pollutants measured included PM 10 (particulate matters with aerodynamic diameter less than 10 μm), total bacteria count (TBC), carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO 2) and sulfur dioxide (SO 2). The indoor and outdoor concentrations of these target air pollutants at these markets were measured and compared. The effects of air conditioning, temperature/relative humidity variation and different stalls on the indoor air quality were also investigated. The results indicated that all of the average indoor concentrations of PM 10, TBC, CO and NO 2 at the markets were below the Hong Kong Indoor Air Quality Objectives (HKIAQO) standards with a few exceptions for PM 10 and TBC. The elevated PM 10 concentrations at Hung Hom, Ngau Tau Kok and Wan Chai markets were probably due to the air filtration of outdoor airborne particulates emitted from vehicular exhaust, whereas high concentrations of airborne bacteria at Sai Ying Pun and Tin Shing markets were linked to the use of air conditioning. Correlation analysis demonstrated that indoor bacteria concentrations were correlated with temperature and relative humidity. The operation of air conditioning did not significantly reduce the levels of air pollutants at the markets. However, the higher indoor/outdoor ratios demonstrated that the operation of air conditioning had influence on the levels of bacteria at the markets. It was found that average PM 10 concentration at poultry stalls was higher than the HKIAQO standard of 180 μg/m 3, and was over two times that measured at vegetable, fish and meat stalls. Furthermore, the concentration of airborne bacteria at the poultry stalls was as high as 1031 CFU/m 3, which was above the HKIAQO standard of 1000 CFU/m 3. The bacteria levels at other three stalls were all below the HKIAQO standard. Statistical analysis indicated that there were no significant differences among the four stalls for CO, NO x and SO 2.

Experimental study of indoor and outdoor airborne bacterial concentrations in Tempe, Arizona, USA

Indoor and outdoor airborne bacterialconcentrations were examined in an occupiedoffice building equipped with an airconditioning (HVAC) system, in Tempe, Arizona,USA. A two-stage microbial air sampler wasused to collect bacteria both inside andoutside the office at fixed locations in space,and at regular time intervals from August toDecember, 2000. Simultaneous measurement ofbacterial concentrations, temperature, relativehumidity, light intensity and wind speed wereperformed to explore the effects ofenvironmental factors on bacteria levels. Tengenera and twenty species of airborne bacteriawere found in our samples. AirborneGram-positive bacteria were most abundant, withmore than 90% of the measured population. Theparticle sizes of most outdoor and indoorairborne bacterial aerosols were larger than8.0 μm. According to the measurements ofeither a typical day or three consecutive days,the concentrations of outdoor airborne bacteriawere highest in the morning, but declined inthe afternoon and reached the lowest point inthe evening. With regard to the effects offour environmental factors – temperature,relative humidity, light intensity, and windspeed, the relative humidity had the mostpronounced influence on the outdoor bacterialconcentration, with the number of bacteriaincreasing sharply on a day of high relativehumidity.

Relationships between Indoor and Outdoor Air Quality in Delhi

The relationship between indoor and outdoor airborne particles was investigated for 24 residential, sensitive, commercial and heavy traffic sites in Delhi, India. Sampling of suspended particulate matter (SPM) was first conducted simultaneously indoors and outdoors at the reference site during February to March 2000, and later at all the sites during February to July 2001. In order to evaluate the heavy metal composition of the SPM, analyses of Mg, Ca, Cu, Cd, Pb, Cr, Mn, Fe and Ni were done by atomic absorption spectrometry (AAS). It was found that the outdoor SPM concentrations do indeed affect the indoor SPM concentrations in varying degrees depending upon the nature of the site. In case of metals Cu, Cr, Cd and Ni, very good correlation between the indoor and outdoor concentrations was observed irrespective of the nature of the site. The correlation between indoor and outdoor for Mg, Fe, Mn and Pb depends upon the nature of the site. No correlation was observed between indoor and outdoor Ca at any of the chosen sites.

Remediation of Hanford’s N-Reactor Liquid Waste Disposal Sites

Hanford's N-Reactor operated from 1963 to 1987 generating approximately 9 x 10 m of radioactive and hazardous liquid effluent as a result of reactor operations. Two liquid waste disposal sites, essentially large trenches designed to filter contaminants from the water as it percolates through the soil column, were established to dispose of the effluent. The discharges to the sites included cooling water from the reactor primary, spent fuel storage, and periphery systems, along with miscellaneous drainage from reactor support facilities. Today, both sites are classified as Treatment Storage and Disposal Facilities under the Resource Conservation and Recovery Act of 1976, which makes them priority sites for remediation. The two sites cover approximately 4,100 m and 9,300 m, respectively. Remediation of the sites requires removing a combined total of approximately 2.6 x 10 kg of contaminated soil and debris. Principal radionuclides contained in the soil/debris are Co, Cs, Pu, and Sr. Remediation of these waste sites requires demolishing concrete structures and excavating, hauling, and disposing of contaminated soils in work areas containing high levels of contamination and whole body dose rates in excess of 1 mSv h. The work presents unique radiological control challenges, such as minimizing external dose to workers in a constantly changing outdoor work environment, maintaining contamination control during removal of a water distribution trough filled with highly contaminated sludge, and minimizing outdoor airborne contamination during size reduction of highly contaminated pipelines. Through innovative approaches to dose reduction and contamination control, Hanford's Environmental Restoration Contractor has met the challenge, completing the first phase on schedule and with a total project exposure below the goal of 0.1 person-Sv.

Outdoor air pollution, climatic changes and allergic bronchial asthma.

Both the prevalence and severity of respiratory allergic diseases such as bronchial asthma have increased in recent years. Among the factors implicated in this "epidemic" are indoor and outdoor airborne pollutants. Urbanisation with its high levels of vehicle emissions and Westernised lifestyle parallels the increase in respiratory allergy in most industrialised countries, and people who live in urban areas tend to be more affected by the disease than those of rural areas. In atopic subjects, exposure to air pollution increases airway responsiveness to aeroallergens. Pollen is a good model with which to study the interrelationship between air pollution and respiratory allergic diseases. Biological aerosols carrying antigenic proteins, such as pollen grains or plant-derived paucimicronic components, can produce allergic symptoms. By adhering to the surface of these airborne allergenic agents, air pollutants could modify their antigenic properties. Several factors influence this interaction, i.e., type of air pollutant, plant species, nutrient balance, climatic factors, degree of airway sensitisation and hyperresponsiveness of exposed subjects. However, the airway mucosal damage and the impaired mucociliary clearance induced by air pollution may facilitate the penetration and the access of inhaled allergens to the cells of the immune system, and so promote airway sensitisation. As a consequence, an enhanced immunoglobulin E-mediated response to aeroallergens and enhanced airway inflammation favoured by air pollution could account for the increasing prevalence of allergic respiratory diseases in urban areas.

Ambient air measurement of acrolein and other carbonyls at the Oakland-San Francisco Bay Bridge toll plaza.

Interest in ambient concentrations of acrolein and other alpha,beta-unsaturated aldehydes and dicarbonyls (e.g., crotonaldehyde, methyl glyoxal, glyoxal, malonaldehyde (malondialdehyde)) is growing because either they exist at high levels in motor vehicle emissions or they arise from photooxidation of other hydrocarbons emitted from mobile sources. In addition, their mutagenic, genotoxic, or carcinogenic properties are well-established, and the results of a dispersion-modeling study regarding the health risks posed by the 188 hazardous air pollutants in California attributes the highest noncancer risk to exposure to acrolein. Such modeling studies, conducted by the U.S. Environmental Protection Agency (U.S. EPA), also predict median ambient air concentrations of acrolein higher than 0.06 microg/m3, the chronic inhalation reference exposure level stipulated by the California Office of Environmental Health Hazard Assessment in counties surrounding the Oakland-San Francisco Bay Bridge. We measured acrolein and other potentially toxic carbonyls in air sampled at the San Francisco Bay Bridge toll plaza during rush hour traffic, which may be considered a "worst case scenario" for outdoor airborne carbonyls. We identified 36 carbonyls in the sample extracts, including 14 saturated aliphatic carbonyls, six unsaturated carbonyls, four aromatic carbonyls, six dicarbonyls, and six hydroxy carbonyls. Structural information to support tentative identification of carbonyls and hydroxycarbonyls was obtained by using a method that involves O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) and PFBHA/bis(trimethylsilyl)trifluoroacetamide (BSTFA) derivatization in concert with gas chromatography/ion trap mass spectrometry. Most notably, we report for the first time the presence of malonaldehyde in the ambient atmospheric environment. A relatively linear relationship between retention time and the molecular weight of the derivatives was established to assist in obtaining structural information about chemicals for which authentic standards are not readily available. Levels of acrolein exceeded the California reference exposure level during morning rush hour traffic. The measured values, however, were significantly lower than estimates of county-wide average acrolein concentrations predicted by a U.S. EPA modeling study based on 1996 data. Successful regulatory efforts such as the introduction of reformulated gasoline, together with the advancement of new catalysts and fleet turnover throughout the 1990s, are likely to account for part of the gap between our determination and the 1996 levels.

ASSOCIATIONS OF POLYCYCLIC ORGANIC MATTER IN OUTDOOR AIR WITH DECREASED BIRTH WEIGHT: A PILOT CROSS-SECTIONAL ANALYSIS

The association between births that are small for gestational age and outdoor airborne polycyclic organic matter (POM) was examined in New Jersey, a highly urban state. This pilot study utilizes a cross-sectional investigation combining maternal and pregnancy outcome information from birth certificates with air toxics data from the U.S. Environmental Protection Agency Cumulative Exposure Project and census data at the census tract level. The exposure categories were based on tertiles of modeled average POM concentrations for each census tract in New Jersey. High POM exposure was positively associated with delivery of "small for gestational age" (SGA) births. After adjustment for potential individual-level confounding factors, the odds ratios for term, preterm, and all SGA were 1.22 (1.16-1.27), 1.26 (1.07-1.49), and 1.22 (1.17-1.27), respectively, for the highest exposure tertile in the urban population of the state (89% of the state's birth population). For group-level variables, the corresponding ORs were 1.12 (1.07-1.18), 1.23 (1.02-1.47), and 1.13 (1.07-1.18). The results of this study suggest that residential exposure to airborne polycyclic organic matter (POM) is associated with increased prevalence of "small for gestational age" births among urban population. Cross-sectional investigations combining air dispersion models with routinely collected population-based health and census data could be a useful approach for identifying the hazardous air pollutants of greatest public health concern.

Outdoor exposure to airborne polycyclic organic matter and adverse reproductive outcomes: a pilot study.

To investigate the association between outdoor airborne polycyclic organic matter (POM) and adverse reproductive outcomes in New Jersey, we used a cross-sectional design combining air quality data from the USA EPA Cumulative Exposure Project and individual data on pregnancy outcomes from birth and fetal death certificates at the census tract level. After excluding plural births and chromosomal anomalies, 221,406 live births and 1,591 fetal deaths registered in New Jersey during the years of 1990 and 1991 were included. The exposure estimates were derived from modeled average POM concentrations for each census tract in the state. After adjustment for potential confounders, the odds ratios (OR) for very low birth weight for the highest exposure compared to the lowest exposure group was 1.31 (95% CI 1.15-1.51); among term births, high POM exposure was associated with low birth weight OR = 1.31 (95% CI 1.21-1.43), with fetal death OR = 1.19 (95% CI 1.02-1.39) and with premature birth OR = 1.25 (95% CI 1.19-1.31). The univariate stratified analyses suggested effect modification of all observed associations by maternal alcohol consumption. This study found associations between outdoor exposure to modeled average airborne POM and several adverse pregnancy outcomes. The data and methods utilized in this pilot study may be useful for identifying hazardous air pollutants requiring in-depth investigation.

The relationship between indoor and outdoor airborne particles in the residential environment

The relationship between indoor and outdoor airborne particles was investigated for 16 residential houses located in a suburban area of Brisbane, Australia. The submicrometer particle numbers were measured using the Scanning Mobility Particle Sizer, the larger particle numbers using the Aerodynamic Particle Sizer and an approximation of PM 2.5 was also measured using a DustTrak. The measurements were conducted for normal and minimum ventilation conditions using simultaneous and non-simultaneous measurement methods designed for the purpose of the study. Comparison of the ratios of indoor to outdoor particle concentrations revealed that while temporary values of the ratio vary in a broad range from 0.2 to 2.5 for both lower and higher ventilation conditions, average values of the ratios were very close to one regardless of ventilation conditions and of particle size range. The ratios were in the range from 0.78 to 1.07 for submicrometer particles, from 0.95 to 1.0 for supermicrometer particles and from 1.01 to 1.08 for PM 2.5 fraction. Comparison of the time series of indoor to outdoor particle concentrations shows a clear positive relationship existing for many houses under normal ventilation conditions (estimated to be about and above 2 h −1), but not under minimum ventilation conditions (estimated to be about and below 1 h −1). These results suggest that for normal ventilation conditions, outdoor particle concentrations could be used to predict instantaneous indoor particle concentrations but not for minimum ventilation, unless air exchange rate is known, thus allowing for estimation of the “delay constant”.

Fungal allergy -clinical aspect-

Fungus is known to be one of the important causative allergens of allergic diseases such as bronchial asthma, allergic rhinitis and atopic dermatitis. Not only outdoor airborne fungi but also indoor fungi such as Aspergillus restrictus and Eurotium have recently received attention as causative fungal allergens of allergic diseases. In addition to careful history taking, in vivo testing methods such as skin test and conjunctival or bronchial provocation tests are sometimes necessary to diagnose the causative allergen. Problems requiring resolution are: 1. fungal allergens composed of multiple allergenic components, 2. difficulty of environmental monitoring of fungal allergens, 3. special characteristics as microorganisms, and 4. characteristics of normal flora allergy, etc.

Capability of air filters to retain airborne bacteria and molds in heating, ventilating and air-conditioning (HVAC) systems

The capability of air filters (filterclass: F6, F7) to retain airborne outdoor microorganisms was examined in field experiments in two heating, ventilating and air conditioning (HVAC) systems. At the beginning of the 15-month investigation period, the first filter stages of both HVAC systems were equipped with new unused air filters. The number of airborne bacteria and molds before and behind the filters were determined simultaneously in 14 days-intervals using 6-stage Andersen cascade impactors. Under relatively dry (< 80 % R. H.) and warm (> 12 °C) outdoor air conditions air filters led to a marked reduction of airborne microorganism concentrations (bacteria by approximately 70 % and molds by > 80 %). However, during long periods of high relative humidity (> 80 % R. H.) a proliferation of bacteria on air filters with subsequent release into the filtered air occured. These microorganisms were mainly smaller than 1.1 μm therefore being part of the respirable fraction. The results showed furthermore that one possibility to avoid microbial proliferation is to limit the relative humidity in the area of the air filters to 80 % R. H. (mean of 3 days), e. g. by using preheaters in front of air filters in HVAC-systems.