Showing papers in "Indoor Air in 2005"

Do indoor pollutants and thermal conditions in schools influence student performance? A critical review of the literature

Abstract: To assess whether school environments can adversely affect academic performance, we review scientific evidence relating indoor pollutants and thermal conditions, in schools or other indoor environments, to human performance or attendance. We critically review evidence for direct associations between these aspects of indoor environmental quality (IEQ) and performance or attendance. Secondarily, we summarize, without critique, evidence on indirect connections potentially linking IEQ to performance or attendance. Regarding direct associations, little strongly designed research was available. Persuasive evidence links higher indoor concentrations of nitrogen dioxide to reduced school attendance, and suggestive evidence links low ventilation rates to reduced performance. Regarding indirect associations, many studies link indoor dampness and microbiologic pollutants (primarily in homes) to asthma exacerbations and respiratory infections, which in turn have been related to reduced performance and attendance. Also, much evidence links poor IEQ (e.g., low ventilation rate, excess moisture, or formaldehyde) with adverse health effects in children and adults and documents dampness problems and inadequate ventilation as common in schools. Overall, evidence suggests that poor IEQ in schools is common and adversely influences the performance and attendance of students, primarily through health effects from indoor pollutants. Evidence is available to justify (1) immediate actions to assess and improve IEQ in schools and (2) focused research to guide IEQ improvements in schools.

Role of air distribution in SARS transmission during the largest nosocomial outbreak in Hong Kong.

Abstract: UNLABELLED Severe acute respiratory syndrome (SARS) is primarily transmitted by bio-aerosol droplets or direct personal contacts. This paper presents a detailed study of environmental evidence of possible airborne transmission in a hospital ward during the largest nosocomial SARS outbreak in Hong Kong in March 2003. Retrospective on-site inspections and measurements of the ventilation design and air distribution system were carried out on July 17, 2003. Limited on-site measurements of bio-aerosol dispersion were also carried out on July 22. Computational fluid dynamics simulations were performed to analyze the bio-aerosol dispersion in the hospital ward. We attempted to predict the air distribution during the time of measurement in July 2003 and the time of exposure in March 2003. The predicted bio-aerosol concentration distribution in the ward seemed to agree fairly well with the spatial infection pattern of SARS cases. Possible improvement to air distribution in the hospital ward was also considered. PRACTICAL IMPLICATIONS Our study revealed the need for the development of improved ventilation and air-conditioning systems in an isolation ward or a general hospital ward for infectious respiratory diseases. The outbreak in Ward 8A, which was in a general hospital and could house nearly 40 patients, demonstrated the cross-infection risks of respiratory infectious diseases in hospitals if a potential highly infectious patient was not identified and isolated. Our example simulation, which extended the SARS Busters' design for an isolation room to Ward 8A, demonstrated that there was room for improvement to minimize cross-infection in large general hospital wards.

Characterization of indoor sources of fine and ultrafine particles: a study conducted in a full-scale chamber.

Abstract: Humans and their activities are known to generate considerable amounts of particulate matter indoors. Some of the activities are cooking, smoking and cleaning. In this study 13 different particle sources were for the first time examined in a 32 m3 full-scale chamber with an air change rate of 1.7 ± 0.1/h. Two different instruments, a condensation particle counter (CPC) and an optical particle counter (OPC) were used to quantitatively determine ultrafine and fine particle emissions, respectively. The CPC measures particles from 0.02 μm to larger than 1.0 μm. The OPC was adjusted to measure particle concentrations in eight fractions between 0.3 and 1.0 μm. The sources were cigarette side-stream smoke, pure wax candles, scented candles, a vacuum cleaner, an air-freshener spray, a flat iron (with and without steam) on a cotton sheet, electric radiators, an electric stove, a gas stove, and frying meat. The cigarette burning, frying meat, air freshener spray and gas stove showed a particle size distribution that changed over time towards larger particles. In most of the experiments the maximum concentration was reached within a few minutes. Typically, the increase of the particle concentration immediately after activation of the source was more rapid than the decay of the concentration observed after deactivation of the source. The highest observed concentration of ultrafine particles was approximately 241,000 particles/cm 3 and originated from the combustion of pure wax candles. The weakest generation of ultrafine particles (1.17 × 107 particles per second) was observed when ironing without steam on a cotton sheet, which resulted in a concentration of 550 particles/cm3 in the chamber air. The highest generation rate (1.47 × 1010 particles per second) was observed in the radiator test.

Relationship between outdoor and indoor air quality in eight French schools.

Abstract: UNLABELLED In the frame of the French national research program PRIMEQUAL (inter-ministry program for better air quality in urban environments), measurements of outdoor and indoor pollution have been carried out in eight schools in La Rochelle (France) and its suburbs. The buildings were naturally ventilated by opening the windows, or mechanically ventilated, and showed various air permeabilities. Ozone, nitrogen oxides (NO and NO(2)), and airborne particle (particle counts within 15 size intervals ranging from 0.3 to 15 mum) concentrations were continuously monitored indoors and outdoors for two 2-week periods. The indoor humidity, temperature, CO(2) concentration (an indicator of occupancy), window openings and building permeability were also measured. The temporal profiles of indoor and outdoor concentrations show ozone and nitrogen oxides behave differently: NO and NO(2) indoor/outdoor concentration ratios (I/O) were found to vary in a range from 0.5 to 1, and from 0.88 to 1, respectively, but no correlation with building permeability was observed. On the contrary, I/O ratios of ozone vary in a range from 0 to 0.45 and seem to be strongly influenced by the building air-tightness: the more airtight the building envelope, the lower the ratio. Occupancy, through re-suspension of previously deposited particles and possible particle generation, strongly influences the indoor concentration level of airborne particles. However, this influence decreases with particle size, reflecting the way deposition velocities vary as a function of size. The influence of particle size on deposition and penetration across the building envelope is also discussed by analyzing the I/O ratios measured when the buildings were unoccupied, by comparing the indoor concentrations measured when the buildings were occupied and when they were not (O/U ratios), and by referring to previously published studies focussing on this topic. Except one case, I/O were found to vary in the range from 0.03 to 1.79. All O/U are greater than one and increase up to 100 with particle size. PRACTICAL IMPLICATIONS Assessing children's total exposure requires the knowledge of outdoor and indoor air contaminant concentrations. The study presented here provides data on compared outdoor and indoor concentration levels in school buildings, as well as information on the parameters influencing the relationship between outdoor and indoor air quality. It may be used as a basis for estimating indoor concentrations from outdoor concentrations data, or as a first step in designing buildings sheltering children against atmospheric pollution.

Dampness at home and its association with airway, nose and skin symptoms among 10 851 preschool children in Sweden: : A cross sectional study

Abstract: Dampness at home and its association with airway, nose and skin symptoms among 10 851 preschool children in Sweden: a cross sectional study

(1-->3)-Beta-D-glucans and respiratory health: a review of the scientific evidence.

Abstract: UNLABELLED (1-->3)-Beta-D-glucan are non-allergenic structural cell wall components of most fungi that have been suggested to play a causal role in the development of respiratory symptoms associated with indoor fungal exposure This review describes the currently available epidemiological literature on health effects of (1-->3)-beta-D-glucan, focusing on atopy, airway inflammation and symptoms, asthma, and lung function In addition to population studies, studies in human volunteers experimentally exposed to (1-->3)-beta-D-glucan are described as well as relevant animal studies Furthermore, the review discusses exposure assessment methods, the potential for exposure control and it concludes with identifying research needs The observational and experimental studies reviewed suggested some association between (1-->3)-beta-D-glucan exposure, airway inflammation and symptoms, however, results were mixed and specific symptoms and potential underlying inflammatory mechanisms associated with exposure could not be identified Large observational studies using well validated exposure assessment methods are needed to further our knowledge regarding the potential health effects of indoor (1-->3)-beta-D-glucan exposure PRACTICAL IMPLICATIONS The currently available epidemiological data do not permit conclusions to be drawn regarding the presence (or absence) of an association between environmental (1-->3)-beta-D-glucan exposure and specific adverse health effects, nor is it clear from the currently available evidence which specific immunological mechanisms underlie the presumed health effects More and larger observational studies are needed to asses whether (1-->3)-beta-D-glucan exposure plays a significant role in respiratory morbidity In addition, existing methods to assess environmental (1-->3)-beta-D-glucan exposure require validation and further development before they can be used routinely in large scale epidemiological studies

Association between ventilation rates in 390 Swedish homes and allergic symptoms in children.

Abstract: UNLABELLED The aim of the study was to test the hypothesis that a low-ventilation rate in homes is associated with an increased prevalence of asthma and allergic symptoms among children. A total of 198 cases (with at least two of three symptoms: wheezing, rhinitis, eczema) and 202 healthy controls, living in 390 homes, were examined by physicians. Ventilation rates were measured by a passive tracer gas method, and inspections were carried out in the homes. About 60% of the multi-family houses and about 80% of the single-family houses did not fulfill the minimum requirement regarding ventilation rate in the Swedish building code (0.5 air changes per hour, ach). Cases had significantly lower ventilation rates than controls and a dose-response relationship was indicated. PRACTICAL IMPLICATIONS A low-ventilation rate of homes may be a risk factor for allergies among children. Families with allergic children should be given the advice to have good ventilation in the home. In investigations, of associations between environmental factors and allergies, the air change rate in homes has to be considered.

Multi‐zone modeling of probable SARS virus transmission by airflow between flats in Block E, Amoy Gardens

Abstract: UNLABELLED More than 300 residents of a private high-rise housing estate were infected with severe acute respiratory syndrome within a short period during the 2003 epidemic in Hong Kong. The outbreak occurred after the identified index patient visited a flat on a middle floor in Block E of the Amoy Gardens estate on two nights. Approximately 45% of the subsequently infected people resided in Block E, while the other 55% of infected cases mainly resided in six other blocks close to Block E. The distribution of the infected flats in Block E conformed to a non-uniform spatial pattern. Probable environmental causes for airborne transmission associated with the air movements between flats in Block E are identified. The well-established multi-zone airflow modeling method was used to analyze the virus-laden bio-aerosol dispersion between flats through door and window leakage areas in Block E under six different scenarios. The distribution of infection risk in Block E matched with the virus concentrations in flats predicted with the use of multi-zone modeling. Our study shows the importance of ventilation design in high-rise residential apartments. PRACTICAL IMPLICATIONS The present study on the Amoy Gardens outbreak presented a scenario in which crowded living spaces might lead to infection disasters. There is a need to improve the current sanitary drainage design and maintenance standards to avoid any leakage of foul gas into the indoor environments. Our study revealed the need for a review of indoor air quality and ventilation design in buildings including offices, homes and hotels. The study has implications to public health in, for example, the control of other airborne respiratory infectious diseases such as influenza, and in bio-terror safety in buildings.

A model predicting the effect of speech of varying intelligibility on work performance.

Abstract: UNLABELLED: Speech is the most distracting sound in (open-plan) offices. Several laboratory studies have shown that speech impairs the performance of, for example, reading and short-term memory. It is not the sound level of speech that determines its distracting power but its intelligibility, which can be physically determined by measuring the Speech Transmission Index (STI). The aim of this study was to develop a mathematical model that predicts how much the performance is reduced due to speech of varying intelligibility. The model was based on the literature according to which performance decrements have been 4-45% depending on the task. The best performance occurs when speech is absent (STI=0.0), and the strongest performance decrement occurs when speech is perfectly heard (STI=1.0). The shape of the performance vs. STI between 0.0 and 1.0 was adopted from the general speech intelligibility theory. The performance starts to decrease when STI exceeds 0.2. Highest performance decrease is reached already when STI exceeds 0.60. PRACTICAL IMPLICATIONS: The prediction model can be exploited in the evaluation of work performance in different acoustical conditions in open-plan offices when STI is known. It can be utilized to promote actions aiming at better acoustical conditions.

Current asthma and respiratory symptoms among pupils in relation to dietary factors and allergens in the school environment

Abstract: Current asthma and respiratory symptoms among pupils in relation to dietary factors and allergens in the school environment.

Field study on occupant comfort and the office thermal environment in rooms with displacement ventilation.

Abstract: UNLABELLED: A field survey of occupants' response to the indoor environment in 10 office buildings with displacement ventilation was performed. The response of 227 occupants was analyzed. About 24% of the occupants in the survey complained that they were daily bothered by draught, mainly at the lower leg. Vertical air temperature difference measured between head and feet levels was less than 3 degrees C at all workplaces visited. Combined local discomfort because of draught and vertical temperature difference does not seem to be a serious problem in rooms with displacement ventilation. Almost one half (49%) of the occupants reported that they were daily bothered by an uncomfortable room temperature. Forty-eight per cent of the occupants were not satisfied with the air quality. PRACTICAL IMPLICATIONS: The PMV and the Draught Rating indices as well as the specifications for local discomfort because of the separate impact of draught and vertical temperature difference, as defined in the present standards, are relevant for the design of a thermal environment in rooms with displacement ventilation and for its assessment in practice. Increasing the supply air temperature in order to counteract draught discomfort is a measure that should be considered carefully; even if the desired stratification of pollution in the occupied zone is preserved, an increase of the inhaled air temperature may have a negative effect on perceived air quality.

A study on VOC source and sink behavior in porous building materials – analytical model development and assessment

Abstract: Building materials can strongly affect indoor air quality. Porous building materials are not only sources of indoor air pollutants such as volatile organic compounds (VOC) but they are also strong sinks of these pollutants. The knowledge of VOC transfer mechanisms in these materials is an important step for controlling the indoor VOC concentration levels, and for determining the optimum ventilation requirements for acceptable IAQ. This study provides a theoretical investigation of primary and secondary VOC source and sink behavior of porous building materials. A new analytical model was developed based on the fundamental theories of mass transfer mechanisms in porous materials. The proposed model considers both primary and secondary source/sink behavior for the first time. The former refers to the transfer of gas-phase and/or physically adsorbed VOC, while the latter refers to the generation or elimination of VOC within the solid because of chemical reactions like oxidation, hydrolysis, chemical adsorption, etc. The proposed model was assessed with experimental data, namely emission tests of carpets and sorption tests of wood chipboard. It was demonstrated that, unlike the existing analytical models, the proposed analytical model could simultaneously account for the effect of air velocity on both VOC source as well as sink behavior. Case studies were then carried out for secondary VOC source behavior. Due to the lack of experimental studies on mechanisms of secondary behavior, hypothetical generation functions were implemented. It was demonstrated that the proposed analytical model is suitable for describing various mechanisms involved in the secondary behavior due to the little limitations imposed on the generation/elimination term. When VOC generation takes place at the material-air interface, the simulation shows that although the primary emission is not affected by air velocity, the secondary emission, however, is clearly affected. This behavior agrees with the available experimental findings on secondary emissions. PRACTICAL IMPLICATION: The analytical model presented in this paper can predict both primary and secondary VOC source (emission) or sink (sorption) behavior of porous building materials. Since the model considers diffusion and adsorption/desorption within the material, and convection over the material surface, the simulation using the model can readily provide the effects of material properties and airflow properties on the primary and/or the secondary behavior, hence, it can provide a better understanding on the mechanisms. This will enable us to keep the indoor VOC concentration within a desirable level.

Effects of moisture‐damage repairs on microbial exposure and symptoms in schoolchildren

Abstract: UNLABELLED: Effects of renovation on symptom prevalence and microbial status were studied in two moisture-damaged schools and in two non-damaged schools with longitudinal cross-sectional surveys before and after repairs. Over 1300 schoolchildren aged 6-17 returned questionnaires before and after repairs. After full renovation in one of the damaged schools, elevated concentrations and increased frequencies of indoor air fungi normalized and a significant decrease in the prevalence of 10 symptoms of 12 studied was observed among schoolchildren. No change in microbial conditions was seen after partial repairs in the other damaged school, and only slight improvement was observed in symptom prevalence. The change in the prevalence of symptoms in the reference schools was minor. The results suggest that increased symptom prevalence among schoolchildren in moisture-damaged schools can be managed with proper repair of the moisture damage. PRACTICAL IMPLICATIONS: This longitudinal intervention study showed the positive effects of the moisture and mold damage repairs of a school building on children's health. The success necessitates however, a thorough renovation including appropriate ventilation. Monitoring of airborne viable microbes revealed the damage status of the building and thus could be used as a tool in evaluating the quality of repairs.

Evaluation of ionic air purifiers for reducing aerosol exposure in confined indoor spaces

Abstract: UNLABELLED Numerous techniques have been developed over the years for reducing aerosol exposure in indoor air environments. Among indoor air purifiers of different types, ionic emitters have gained increasing attention and are presently used for removing dust particles, aeroallergens and airborne microorganisms from indoor air. In this study, five ionic air purifiers (two wearable and three stationary) that produce unipolar air ions were evaluated with respect to their ability to reduce aerosol exposure in confined indoor spaces. The concentration decay of respirable particles of different properties was monitored in real time inside the breathing zone of a human manikin, which was placed in a relatively small (2.6 m3) walk-in chamber during the operation of an ionic air purifier in calm air and under mixing air condition. The particle removal efficiency as a function of particle size was determined using the data collected with a size-selective optical particle counter. The removal efficiency of the more powerful of the two wearable ionic purifiers reached about 50% after 15 min and almost 100% after 1.5 h of continuous operation in the chamber under calm air conditions. In the absence of external ventilation, air mixing, especially vigorous one (900 CFM), enhanced the air cleaning effect. Similar results were obtained when the manikin was placed inside a partial enclosure that simulated an aircraft seating configuration. All three stationary ionic air purifiers tested in this study were found capable of reducing the aerosol concentration in a confined indoor space. The most powerful stationary unit demonstrated an extremely high particle removal efficiency that increased sharply to almost 90% within 5-6 min, reaching about 100% within 10-12 min for all particle sizes (0.3-3 microm) tested in the chamber. For the units of the same emission rate, the data suggest that the ion polarity per se (negative vs. positive) does not affect the performance but the ion emission rate does. The effects of particle size (within the tested range) and properties (NaCl, PSL, Pseudomonas fluorescens bacteria) as well as the effects of the manikin's body temperature and its breathing on the ionic purifier performance were either small or insignificant. The data suggest that the unipolar ionic air purifiers are particularly efficient in reducing aerosol exposure in the breathing zone when used inside confined spaces with a relatively high surface-to-volume ratio. PRACTICAL IMPLICATIONS Ionic air purifiers have become increasingly popular for removing dust particles, aeroallergens and airborne microorganisms from indoor air in various settings. While the indoor air cleaning effect, resulting from unipolar and bipolar ion emission, has been tested by several investigators, there are still controversial claims (favorable and unfavorable) about the performance of commercially available ionic air purifiers. Among the five tested ionic air purifiers (two wearable and three stationary) producing unipolar air ions, the units with a higher ion emission rate provided higher particle removal efficiency. The ion polarity (negative vs. positive), the particle size (0.3-3 microm) and properties (NaCl, PSL, Pseudomonas fluorescens bacteria), as well as the body temperature and breathing did not considerable affected the ionization-driven particle removal. The data suggest that the unipolar ionic air purifiers are particularly efficient in reducing aerosol exposure in the breathing zone when they are used inside confined spaces with a relatively high surface-to-volume ratio (such as automobile cabins, aircraft seating areas, bathrooms, cellular offices, small residential rooms, and animal confinements). Based on our experiments, we proposed that purifiers with a very high ion emission rate be operated in an intermittent mode if used indoors for extended time periods. As the particles migrate to and deposit on indoor surfaces during the operation of ionic air purifiers, some excessive surface contamination may occur, which introduces the need of periodic cleaning these surfaces.

Concentrations of airborne culturable bacteria in 100 large US office buildings from the BASE study.

Abstract: This paper presents summary statistics of airborne culturable bacteria from the US Environmental Protection Agency Building Assessment Survey and Evaluation (BASE) study. Air samples were collected with single-stage, multiple-hole, agar impactors in 100 large office buildings in 1994-1998 to obtain normative data on indoor environmental quality. Bacterial concentra- tions were compared by incubation temperature, location, season, and climate zone. Forty-one percent of the samples were below the 2- or 5-min detection limits (18 or 7 CFU/m 3 , respectively) but less than 1% were overgrown. Mesophilic bacteria (30� C) accounted for >95% of culturable bacteria, both indoors and outdoors. Average concentrations were higher outdoors, except for Gram-positive cocci, which were the only group that were significantly higher indoors (39 vs. 24 CFU/m 3 ), and Gram-negative cocci, for which both con- centrations were low and the difference were not significant. Outdoor concen- trations of culturable bacteria were somewhat higher in winter (194 vs.165 CFU/m 3 ), and the two dominant outdoor groups were unknown bac- teria and Gram-positive rods. Conversely, indoor concentrations were signifi- cantly higher in summer (116 vs. 87 CFU/m 3 ), consisting primarily of unknown bacteria and Gram-positive cocci. Bacterial concentrations were within the ranges reported in previous studies of non-problem buildings, and the extreme aggregated indoor concentrations (e.g. the 90th percentile, 175 CFU/m 3 )o f these 100 representative buildings may serve as upper bounds to develop interpretation guidelines for office environments and similar non-manufacturing workplaces in various climate zones.

Effects of an ozone-generating air purifier on indoor secondary particles in three residential dwellings.

Abstract: UNLABELLED The use of indoor ozone generators as air purifiers has steadily increased over the past decade. Many ozone generators are marketed to consumers for their ability to eliminate odors and microbial agents and to improve health. In addition to the harmful effects of ozone, recent studies have shown that heterogeneous and homogeneous reactions between ozone and some unsaturated hydrocarbons can be an important source of indoor secondary pollutants, including free radicals, carbonyls, carboxylic acids, and fine particles. Experiments were conducted in one apartment and two detached single-family dwellings in Austin, TX, to assess the effects of an ozone generator on indoor secondary organic aerosol concentrations in actual residential settings. Ozone was generated using a commercial ozone generator marketed as an air purifier, and particle measurements were recorded before, during, and after the release of terpenes from a pine oil-based cleaning product. Particle number concentration, ozone concentration, and air exchange rate were measured during each experiment. Particle number and mass concentrations increased when both terpenes and ozone were present at elevated levels. Experimental results indicate that ozone generators in the presence of terpene sources facilitate the growth of indoor fine particles in residential indoor atmospheres. Human exposure to secondary organic particles can be reduced by minimizing the intentional release of ozone, particularly in the presence of terpene sources. PRACTICAL IMPLICATIONS Past studies have shown that ozone-initiated indoor chemistry can lead to elevated concentrations of fine particulate matter, but have generally been completed in controlled laboratory environments and office buildings. We explored the effects of an explicit ozone generator marketed as an air purifier on the formation of secondary organic aerosol mass in actual residential indoor settings. Results indicate significant increases in number and mass concentrations for particles <0.7 microns in diameter, particularly when an ozone generator is used in the presence of a terpene source such as a pine oil-based cleaner. These results add evidence to the potentially harmful effects of ozone generation in residential environments.

A study of reactive oxygen species in mainstream of cigarette

Abstract: Reactive oxygenated species (ROS) not only exist in living organisms, they also exist in our environment. Combustion process and photochemical reactions are the major source of environmental ROS, and combustion process produced ROS has been gradually gaining attention in recent years. The purpose of this study is to determine the concentrations of ROS in the mainstream smoke of cigarettes sold in the marketplace using the DCFH2 fluorescence method and to understand particulate and gaseous concentrations of ROS. This research will also discuss the relationship between ROS and nicotine, found in popular cigarette brands, as well as the effectiveness of cigarette filters to remove ROS. Results indicate that the ROS concentration of mainstream smoke is 18.64- 54.81 nmol H2O2/l while the correlation coefficients of nicotine and tar to total ROS are 0.959 and 0.909, respectively. Gaseous ROS concentrations are 14.32- 39.03 nmol H2O2/l, and make up 71.21-85.99% of the total. It can be clearly seen therefore, that ROS exist mainly in the gaseous phase. Particulate ROS is dominant at PM2.5 (ROSTSP/ROSPM2.5 is 0.652-0.959). The experimental results involving the tobacco leaves and cigarette ash show that ROS in mainstream smoke comes from the combustion process and not from the tobacco leaves. There is no effective means of eliminating ROS from mainstream smoke, regardless of whether a cigarette filter contains active charcoal.

Ventilation in public housing: implications for indoor nitrogen dioxide concentrations

Abstract: UNLABELLED Although elevated nitrogen dioxide (NO2) exposures may exacerbate asthma, few studies have examined indoor NO2 levels in low-income, urban neighborhoods, where asthma prevalence is high. As part of the Healthy Public Housing Initiative, NO2 was measured in 77 homes within three Boston public housing developments, using Palmes tubes placed in the kitchen, living room, and outdoors. Air exchange rates (AERs) were assessed using a perfluorocarbon tracer technique. Overall NO2 levels were [mean (ppb)+/-s.d.]: kitchen (43+/-20, n=100), living room (36+/-17, n=102), outdoor (19+/-6, n=91). Indoor NO2 levels were significantly higher in the heating season (living room: 43 ppb vs. 26 ppb, kitchen: 50 ppb vs. 33 ppb), while AERs were significantly lower in the heating season (medians 0.49/h vs. 0.85/h). Significant univariate predictors of indoor concentrations include: outdoor NO2 levels, AERs, and occupancy. AERs and outdoor NO2 remained significant in multivariate models (P<0.05). A dummy variable for supplemental heating with gas stove was not significant (P=0.14), but had a large, positive coefficient. Indoor NO2 levels in this cohort are higher than those generally reported in residential US settings, associated in part with increased gas stove usage and decreased AERs during the heating season. PRACTICAL IMPLICATIONS Indoor air quality is mainly a function of outdoor concentrations, indoor sources, ventilation, and residential behavior. Indoor exposures to nitrogen dioxide and other combustion pollutants may be elevated within low-income housing developments due to the presence of multiple sources, poor ventilation, small apartment size, and behavioral responses to apartment conditions (e.g. supplemental heating with gas stove). This information may be used by housing authorities and other landlords to decrease potential environmental stressors, through interventions such as source substitution and improved ventilation, particularly for sensitive sub-populations such as asthmatics.

Of microbes and men

Abstract: UNLABELLED Moisture accumulation in building structures, the microbial ecology of water-damaged sites and human exposure to biological contaminants are complex phenomena and may result in various types of indoor air pollution and adverse health outcomes. Commonly reported are building-related irritation symptoms, respiratory infections and non-specific symptoms and occasionally neurological impairment. Various diseases have been associated with mold exposure, e.g. an increased risk of asthma development and exacerbation as well as clusters of hypersensitivity pneumonitis, pulmonary hemorrhage in infants and rheumatic diseases. The causal agents of these illnesses, still poorly understood, may be linked to the complex interactions between bacteria and fungi with environmental growth substrates and other microorganisms which lead to a wide diversity of exposures. Fungi and bacteria growing on building materials may produce toxic secondary metabolites, and the material appears to be a key determinant of metabolite production. Modern building technology has provided new ecological niches for microbes which readily exploit faults in moisture control. To better describe microbial exposures in buildings, current method development focuses on chemical markers of biomass and assays for specific genetic sequences. PRACTICAL IMPLICATIONS Dampness and moisture phenomena in buildings, resulting microbial and chemical exposures and individual human responses are complex phenomena. While the causative links between exposing agents and health responses are still not well understood, the essential issue is to prevent the problems with good design, construction and maintenance.

Indoor/outdoor relationships for PM2.5 and associated carbonaceous pollutants at residential homes in Hong Kong - case study.

Abstract: UNLABELLED Six residences were selected (two roadside, two urban, and two rural) to evaluate the indoor-outdoor characteristics of PM(2.5) (aerodynamic diameter <2.5 microm) carbonaceous species in Hong Kong during March and April 2004. Twenty-minute-averaged indoor and outdoor PM(2.5) concentrations were recorded by DustTrak samplers simultaneously at each site for 3 days to examine diurnal variability of PM(2.5) mass concentrations and their indoor-to-outdoor (I/O) ratios. Daily (24-h average) indoor/outdoor PM(2.5) samples were collected on pre-fired quartz-fiber filters with battery-powered portable mini-volume samplers and analyzed for organic and elemental carbon (OC, EC) by thermal/optical reflectance (TOR) following the Interagency Monitoring of Protected Visual Environments (IMPROVE) protocol. The average indoor and outdoor concentrations of 24 h PM(2.5) were 56.7 and 43.8 microg/m(3), respectively. The short-term PM(2.5) profiles indicated that the penetration of outdoor particles was an important contributor to indoor PM(2.5), and a household survey indicated that daily activities were also sources of episodic peaks in indoor PM(2.5). The average indoor OC and EC concentrations of 17.1 and 2.8 microg/m(3), respectively, accounted for an average of 29.5 and 5.2%, respectively, of indoor PM(2.5) mass. The average indoor OC/EC ratios were 5.8, 9.1, and 5.0 in roadside, urban, and rural areas, respectively; while average outdoor OC/EC ratios were 4.0, 4.3, and 4.0, respectively. The average I/O ratios of 24 h PM(2.5), OC, and EC were 1.4, 1.8, and 1.2, respectively. High indoor-outdoor correlations (r(2)) were found for PM(2.5) EC (0.96) and mass (0.81), and low correlations were found for OC (0.55), indicative of different organic carbon sources indoors. A simple model implied that about two-thirds of carbonaceous particles in indoor air are originated from outdoor sources. PRACTICAL IMPLICATIONS Indoor particulate pollution has received more attentions in Asia. This study presents a case study regarding the fine particulate matter and its carbonaceous compositions at six residential homes in Hong Kong. The characteristics and relationship of atmospheric organic and elemental carbon were discussed indoors and outdoors. The distribution of eight carbon fractions was first reported in indoor samples to interpret potential sources of indoor carbonaceous particles. The data set can provide significant scientific basis for indoor air quality and epidemiology study in Hong Kong and China.

Comparison of formaldehyde emission from building finishing materials at various temperatures in under heating system; ONDOL

Abstract: UNLABELLED The objective of this research was to investigate the effect of various temperatures, room, 37 and 50 degrees C, on formaldehyde emission from floor materials, such as laminate and plywood floorings, and furniture materials, such as MDF and particleboard veneered with decorative paper foil, by desiccator's method. The temperature conditions were set up by, measuring the temperature in a Korean under heating system. To maintain an indoor air temperature of 20 degrees C, the temperature of the flooring surface was about 37 degrees C and the temperature of the cement mortar was 50 degrees C. The initial formaldehyde emission of the laminate flooring and plywood flooring was 1.44 and 0.63 mg/l, and for MDF and particleboard it was 4.73 and 4.95 mg/l, respectively. Floor materials were under E1 grade while furniture materials were under E2 grade in terms of formaldehyde emission. Because of the under heating system, the flooring materials were exposed to 37 and 50 degrees C, while the furniture materials mostly existed at room temperature. At 37 and 50 degrees C, the formaldehyde emission level of the flooring materials was already under 0.3 ppm (F level by JIS A 1460, application possibility without area limit) after 10 days and the emission had decreased further (0.03-0.10 mg/l) after 28 days. These levels are not injurious to the human body and will not cause sick house syndrome (SHS). The problem, however, is the furniture materials such as MDF and particleboard. As these materials are not exposed to high temperature (50 degrees C in this experiment) in living condition, it was still E2 grade of formaldehyde emission level at room temperature remained even after 28 days. Although there will be variations with the volume of furniture materials and the indoor conditions, furniture materials are the principal cause of indoor air quality pollution in Korean with the under heating system. PRACTICAL IMPLICATIONS Koreans spend most of their time sitting on ONDOL (heated) floors, with their buttocks always in contact with the floor surface. The flooring materials are exposed to high temperatures (37-50 degrees C) why the effect of bake-out is rapid. The emission of formaldehyde from furniture materials are more important for the IAQ because usually MDF and particleboard of E2 grade are being used as furniture materials in Korea.

Reduction potential of urban PM2.5 mortality risk using modern ventilation systems in buildings

Abstract: UNLABELLED Urban PM2.5 (particulate matter with aerodynamic diameter smaller than 2.5 microm) is associated with excess mortality and other health effects. Stationary sources are regulated and considerable effort is being put into developing low-pollution vehicles and environment-friendly transportation systems. While waiting for technological breakthroughs in emission controls, the current work assesses the exposure reductions achievable by a complementary means: efficient filtration of supply air in buildings. For this purpose infiltration factors for buildings of different ages are quantified using Exposures of Adult Urban Populations in Europe Study (EXPOLIS) measurements of indoor and outdoor concentrations in a population-based probability sample of residential and occupational buildings in Helsinki, Finland. These are entered as inputs into an evaluated simulation model to compare exposures in the current scenario with an alternative scenario, where the distribution of ambient PM2.5 infiltration factors in all residential and occupational buildings are assumed to be similar to the subset of existing occupational buildings using supply air filters. In the alternative scenario exposures to ambient PM2.5 were reduced by 27%. Compared with source controls, a significant additional benefit is that infiltration affects particles from all outdoor sources. The large fraction of time spent indoors makes the reduction larger than what probably can be achieved by local transport policies or other emission controls in the near future. PRACTICAL IMPLICATIONS It has been suggested that indoor concentrations of ambient particles and the associated health risks can be reduced by using mechanical ventilation systems with supply air filtering in buildings. The current work quantifies the effects of these concentration reductions on population exposures using population-based data from Helsinki and an exposure model. The estimated exposure reductions suggest that correctly defined building codes may reduce annual premature mortality by hundreds in Finland and by tens of thousands in the developed world altogether.

Using large eddy simulation to study particle motions in a room.

Abstract: UNLABELLED As people spend most of their time in an indoor environment, it is important to predict indoor pollutant level in order to assess health risks. As particles are an important pollutant indoors, it is of great interest to study the airflow pattern and particle dispersion in buildings. This study uses large eddy simulation (LES) to predict three-dimensional and transient turbulent flows and a Lagrangian model to compute particle trajectories in a room. The motion of three different types of solid particles in a decaying homogeneous isotropic turbulent airflow is calculated. By comparing the computed results with the experimental data from the literature, the computational method used in this investigation is found to be successful in predicting the airflow and particle trajectories in terms of the second-order statistics, such as the mean-square displacement and turbulent intensity. This Lagrangian model is then applied to the study of particles' dispersion in a ventilated cavity with a simplified geometry for two ventilation scenarios. It is shown that light particles follow the airflow in the room and many particles are exhausted, while heavier particles deposit to the floor or/and are exhausted. PRACTICAL IMPLICATIONS The results of this paper can be used to study dispersion of infectious diseases in enclosed spaces in which virus or bacteria are often attached to particles and transported to different rooms in a building through ventilation systems. In most of studies, the virus or bacteria have been considered to be gaseous phase so there is no slip between virus/bacteria and air. The results in this paper show that heavier particles are submitted to gravity and are sensitive to the ventilation strategy.

Mouse and cockroach allergens in the dust and air in northeastern United States inner-city public high schools.

Abstract: UNLABELLED Considering that high school students spend a large proportion of their waking hours in the school environment, this could be an important location for exposure to indoor allergens. We have investigated the levels of mouse and cockroach allergens in the settled dust and air from 11 schools in a major northeastern US city. Settled dust samples were vacuumed from 87 classrooms, three times throughout the school year. Two separate air samples (flow = 2.5 lpm) were collected by 53 students over a 5-day period from both their school and their home. Mouse allergen (MUP) in the dust varied greatly between schools with geometric means ranging from 0.21 to 133 microg/g. Mouse allergen was detectable in 81% of the samples collected. Cockroach allergen (Bla g 2) ranged from below limit of detection ( 0.003 microg/g) in 71% of the dust samples. Bla g 2 was detected in 22% of airborne samples from the schools. By comparison, mouse allergen was only detected in 5%. These results indicate that the school may be an important location for exposure to allergens from mice and cockroaches and is an indoor environment that should be considered in an overall allergen intervention strategy. PRACTICAL IMPLICATIONS To date, cockroach and mouse allergen intervention strategies have been mainly focused on the home environment. Considering that children spend a significant amount of time in schools, some studies have assessed cockroach allergen levels in schools. This study provides a clearer picture of the distribution and variability of not only cockroach allergen, but also mouse allergen in the school environment. In addition, this study describes limitations of personal air sampling in a student population. Our results suggest that although cockroach and mouse allergens are commonly recovered in classroom dust samples of inner city schools, cockroach allergens are recovered in the personal air samples with a greater frequency relative to mouse allergens.

Multicriteria analysis of health, comfort and energy-efficiency of buildings

Abstract: In order to cope with sustainable development policy, buildings should be at least healthy, comfortable and energy efficient. Criteria for assessing individually the occupant's perceived health, the provided thermal, visual, acoustical comfort, the indoor air quality and the energy efficiency are known. This paper proposes a methodology to perform a global evaluation of a building with regard to all these criteria. This methodology is applied to 97 apartment build-ings and 64 office buildings audited within the HOPE European project to sort, out of these samples, a set of best buildings and a set of buildings that are not acceptable for comfort, per-ceived health and energy use. Some significant differences between these two groups of build-ings are presented.

Novel insight into VOC removal performance of photocatalytic oxidation reactors

Abstract: A general model has been developed for analyzing the removal of volatile organic compounds (VOCs) by photocatalytic oxidation (PCO) reactors, taking into consideration of the photocatalytic (surface) reaction and the con- vective mass transfer coefficients including allowance for their spatial depend- ence. On this basis, a novel insight into VOC removal performance of PCO reactors is presented. The key parameter for evaluating PCO reactor VOC removal performance is the number of the mass transfer unit (NTUm), which is shown to be a simple linear product of three dimensionless parameters: the ratio of the reaction area to the cross-sectional area of the flow channel (A*), the Stanton number of mass transfer (Stm), and the reaction effectiveness (g). The A* represents the geometric and structural characteristic of a PCO reactor. The Stm shows the synergistic degree of alignment between the fluid and mass flow fields, and reflects the convective mass transfer rate of the reactor. The g, describes the relative intensity between the PCO reaction rate and the mass transfer rate. By using the relationship and the parameters, the influence of various factors on the VOC removal performance, the bottleneck for improving the performance and design of a PCO reactor can be determined. Three examples are used to illustrate the application of our proposed model. It is found that the VOC removal bottleneck is the reaction rate for honeycomb type reactor, while mass transfer rate for light-in-tube type reactor. With six fins the fractional conversion of a light-in-tube reactor increases about 70% relative to the one without any fins.

A comparison of airborne ergosterol, glucan and Air‐O‐Cell data in relation to physical assessments of mold damage and some other parameters

Abstract: UNLABELLED We report here a comparison of long duration air samples in 110 homes where the material collected on open faced filter cassettes was analyzed for beta 1,3-d glucan, ergosterol, cholesterol and endotoxin. These data were then compared to careful estimates of visible mold and Air-O-Cell data. All the values found except cholesterol were of a similar magnitude to values reported in the limited number of studies available. Glucan was measured with a factor G based assay of the Limulus Amebocyte Lysate followed by size exclusion chromatography. This showed that the majority of airborne glucan found in these houses was fungal in origin arising from both yeasts and intact spores, as well as hyphal and spore fragments. Hyphal and spore fragments together represented 16% of the intact spore counts but over a broad range. Correlations between airborne glucan were strong for ergosterol and visible mold. However, airborne ergosterol was more highly correlated to visible mold than glucan. Endotoxin and Air-O-Cell measurements were poorly or not related to the other measures in the study. This study provides confidence that long duration air samples of the toxin glucan and ergosterol are related to building damage. PRACTICAL IMPLICATIONS Some studies of damp buildings have shown a relationship between extent of water/mold damage and symptoms. This study compared long duration air samples for glucan and ergosterol to extent of visible mold in houses measuring also the nature of the glucans present. Both measures were highly correlated to extent of visible mold damage in the houses; ergosterol was somewhat superior. Spore counts or prevalence of Asp/Pen in Air-O-Cell samples was not related to extent of visible mold damage but the observation of hyphal fragments was more likely when mold damage was present. This indicates that rigorous assessment of mold damage is a useful measure.

Risk factors for mold in housing: a national survey.

Abstract: UNLABELLED A national random telephone survey was undertaken to determine the prevalence of reported mold in New Zealand houses and the risk factors for it. A total of 613 households provided responses. Mold in one or more rooms was reported by 35.1% of respondents in the sample. House design and construction factors that were independently associated with reported mold in the multivariate analysis included: poorer house condition, older house age (>22 years), relative lack of sun exposure, and having no insulation (e.g. for poorer house condition: odds ratio=1.97, 95% CI=1.25, 3.11). Univariate analyses also showed increased risk associated with high locality rainfall, and living in the most northern part of the country. The number of residents was significantly associated with reported mold in the multivariate analysis as were various behaviors in the univariate analysis (i.e. frequency of baths, showering and clothes washing). The high prevalence of unflued gas heating (32.9%) found in this sample is of potential concern given the potential respiratory hazards. Although this survey has a number of limitations, it does suggest that there are a number of potentially modifiable risk factors for mold that could be reduced by a range of policy responses. PRACTICAL IMPLICATIONS While further research is desirable, the available evidence associated with the health and other adverse impacts of both mold and dampness would favor additional policy responses by government. These could include changes to regulations around housing design including house position, access to sunlight, and level of insulation. The extension of low interest loans for insulation or subsidized installation can help to increase its level of use. Restrictions on the sales of unflued gas heaters could also be considered. A mass media campaign could also be used to inform the population of the readily modifiable risk factors for mold growth and dampness.

Changing microbial concentrations are associated with ventilation performance in Taiwan's air-conditioned office buildings.

Abstract: UNLABELLED Our study conducted serial environmental measurements in 12 large office buildings with two different ventilation designs to obtain airborne microbial concentrations in typical office buildings, and to examine the effects of occupant density, ventilation type and air exchange efficiency on indoor microbial concentrations. Duplicate samples of airborne fungi and bacteria, a total of 2477 measurements, were collected based on a scheme of conducting sampling three times a day for at least seven consecutive days at every study building. Air change rates (ACHs) were also estimated by tracer gas concentration decay method, and measured by continuous Multi-Gas monitor for each building. Most sampling sites were with total fungal and bacteria concentrations higher than 1000 CFU/m(3), an often-quoted guideline in earlier research. Significantly higher concentrations of fungi and bacteria, as well as higher indoor/outdoor (I/O) ratios across most groups of airborne microbes, were identified in buildings with fan coil unit (FCU) system than those with air-handling unit (AHU) system (Student's t test, P < 0.0001). Older buildings and higher air exchange rates were statistically associated with greater indoor bacteria levels in FCU ventilated buildings (R(2) = 0.452); a pattern not found in AHU buildings. Increasing ACH seemed to be the determinant factor for rising indoor fungal and Cladosporium concentrations in those FCU buildings (R(2) = 0.346; 0.518). Our data indicated that FCU ventilated buildings might have provided more outdoor matters into indoor environments through direct penetration of outdoor air. Results also demonstrated a quantitative association between rising numbers of occupants and increasing indoor levels of yeast in both FCU and AHU ventilated buildings. The regression model identified in this study may be considered a reference value for proposing an optimal ACH, while with adequate filtration of fresh air, as an effective strategy in lowering indoor microbial concentrations in air-conditioned buildings. PRACTICAL IMPLICATIONS As control of indoor microbial contamination has become an increasing concern around the world, feasibility and effectiveness of adopting ventilation approach has attracted a significant interest. This field investigation demonstrated, quantitatively, critical variables to be taken into consideration while applying such a measure, including the kinds of microbes to be removed and the types of ventilation system already in place.

Association of air‐conditioning with respiratory symptoms in office workers in tropical climate

Abstract: UNLABELLED To evaluate the association of heating, ventilation and air-conditioning systems (HVAC) and respiratory symptoms in a tropical city, self-administered questionnaires were given to 2000 individuals working in air-conditioned office buildings and to 500 control workers in naturally ventilated buildings. Reported symptoms from the two populations were analyzed using chi-square tests, univariate and multiple logistic regressions models. Symptoms were the outcome variable and the odds ratios were adjusted by gender, age, accumulated work time, smoking habits and atopic background. There was a 79.8% response rate and there was a positive association of nasal symptoms (odds ratio, OR = 1.59, 95% confidence interval, CI = 1.11-2.28), naso-ocular symptoms (OR = 1.58, 95% CI = 1.05-2.38), persistent cough (OR = 3.04, 95% CI = 2.00-4.63) sinusitis symptoms (OR = 1.85, 95% CI = 1.27-2.71) and building-related worsening of the symptoms (OR = 4.92, 95% CI = 2.93-8.27) with working in air-conditioned buildings. In conclusion, our study suggests that artificial air-conditioning is a matter of concern for respiratory symptoms in cities with hot and humid climate. PRACTICAL IMPLICATIONS This study suggests that indoor air-related respiratory symptoms are a matter of concern in places with hot and humid climate. The regression models were adjusted by confounders that could be used in further reanalysis of indoor air quality related symptoms and ventilation systems with expanded variety of climatic conditions.