Showing papers in "Indoor Air in 2013"

Does e‐cigarette consumption cause passive vaping?

Abstract: Electronic cigarette consumption (vaping) is marketed as an alterna- tive to conventional tobacco smoking. Technically, a mixture of chemicals containing carrier liquids, flavors, and optionally nicotine is vaporized and in- haled. The present study aims at the determination of the release of volatile organic compounds (VOC) and (ultra)fine particles (FP/UFP) from an e-ciga- rette under near-to-real-use conditions in an 8-m 3 emission test chamber. Fur- thermore, the inhaled mixture is analyzed in small chambers. An increase in FP/ UFP and VOC could be determined after the use of the e-cigarette. Prominent components in the gas-phase are 1,2-propanediol, 1,2,3-propanetriol, diacetin, flavorings, and traces of nicotine. As a consequence, passive vaping must be expected from the consumption of e-cigarettes. Furthermore, the inhaled aerosol undergoes changes in the human lung that is assumed to be attributed to deposition and evaporation.

Progress in thermal comfort research over the last twenty years

Abstract: Climate change and the urgency of decarbonizing the built environment are driving technological innovation in the way we deliver thermal comfort to occupants. These changes, in turn, seem to be setting the directions for contemporary thermal comfort research. This article presents a literature review of major changes, developments, and trends in the field of thermal comfort research over the last 20 years. One of the main paradigm shift was the fundamental conceptual reorientation that has taken place in thermal comfort thinking over the last 20 years; a shift away from the physically based determinism of Fanger's comfort model toward the mainstream and acceptance of the adaptive comfort model. Another noticeable shift has been from the undesirable toward the desirable qualities of air movement. Additionally, sophisticated models covering the physics and physiology of the human body were developed, driven by the continuous challenge to model thermal comfort at the same anatomical resolution and to combine these localized signals into a coherent, global thermal perception. Finally, the demand for ever increasing building energy efficiency is pushing technological innovation in the way we deliver comfortable indoor environments. These trends, in turn, continue setting the directions for contemporary thermal comfort research for the next decades.

Indoor aerosols: from personal exposure to risk assessment

Abstract: Motivated by growing considerations of the scale, severity, and risks associated with human exposure to indoor particulate matter, this work reviewed existing literature to: (i) identify state-of-the-art experimental techniques used for personal exposure assessment; (ii) compare exposure levels reported for domestic/school settings in different countries (excluding exposure to environmental tobacco smoke and particulate matter from biomass cooking in developing countries); (iii) assess the contribution of outdoor background vs indoor sources to personal exposure; and (iv) examine scientific understanding of the risks posed by personal exposure to indoor aerosols. Limited studies assessing integrated daily residential exposure to just one particle size fraction, ultrafine particles, show that the contribution of indoor sources ranged from 19% to 76%. This indicates a strong dependence on resident activities, source events and site specificity, and highlights the importance of indoor sources for total personal exposure. Further, it was assessed that 10-30% of the total burden of disease from particulate matter exposure was due to indoor-generated particles, signifying that indoor environments are likely to be a dominant environmental factor affecting human health. However, due to challenges associated with conducting epidemiological assessments, the role of indoor-generated particles has not been fully acknowledged, and improved exposure/risk assessment methods are still needed, together with a serious focus on exposure control.

Association of Classroom Ventilation with Reduced Illness Absence: A Prospective Study in California Elementary Schools

Abstract: Author(s): Mendell, MJ; Eliseeva, EA; Davies, MM; Spears, M; Lobscheid, A; Fisk, WJ; Apte, MG | Abstract: Limited evidence associates inadequate classroom ventilation rates (VRs) with increased illness absence (IA). We investigated relationships between VRs and IA in California elementary schools over two school years in 162 3rd-5th-grade classrooms in 28 schools in three school districts: South Coast (SC), Bay Area (BA), and Central Valley (CV). We estimated relationships between daily IA and VR (estimated from two year daily real-time carbon dioxide in each classroom) in zero-inflated negative binomial models. We also compared IA benefits and energy costs of increased VRs. All school districts had median VRs below the 7.1 l/s-person California standard. For each additional 1 l/s-person of VR, IA was reduced significantly (pl0.05) in models for combined districts (-1.6%) and for SC (-1.2%), and nonsignificantly for districts providing less data: BA (-1.5%) and CV (-1.0%). Assuming associations were causal and generalizable, increasing classroom VRs from the California average (4 l/s-person) to the State standard would decrease IA by 3.4%, increase attendance-linked funding to schools by $33 million annually, and increase costs by only $4 million. Further increasing VRs would provide additional benefits. These findings, while requiring confirmation, suggest that increasing classroom VRs above the State standard would substantially decrease illness absence and produce economic benefits. Published 2013. This article is a US Government work and is in the public domain in the USA.

Health benefits of particle filtration

Abstract: The evidence of health benefits of particle filtration in homes and commercial buildings is reviewed. Prior reviews of papers published before 2000 are summarized. The results of 16 more recent intervention studies are compiled and analyzed. Also, reviewed are four studies that modeled health benefits of using filtration to reduce indoor exposures to particles from outdoors. Prior reviews generally concluded that particle filtration is, at best, a source of small improvements in allergy and asthma health effects; however, many early studies had weak designs. A majority of recent intervention studies employed strong designs and more of these studies report statistically significant improvements in health symptoms or objective health outcomes, particularly for subjects with allergies or asthma. The percentage improvement in health outcomes is typically modest, for example, 7% to 25%. Delivery of filtered air to the breathing zone of sleeping allergic or asthmatic persons may be more consistently effective in improving health than room air filtration. Notable are two studies that report statistically significant improvements, with filtration, in markers that predict future adverse coronary events. From modeling, the largest potential benefits of indoor particle filtration may be reductions in morbidity and mortality from reducing indoor exposures to particles from outdoor air.

PVC flooring is related to human uptake of phthalates in infants.

Abstract: Poly Vinyl Chloride (PVC) flooring material contains phthalates and it has been shown that such materials are important sources for phthalates in indoor dust. Phthalates are suspected endocrine disrupting chemicals (EDCs). Consecutive infants between two and six months old and their mothers were invited. A questionnaire about indoor environmental factors and family life style was used. Urinary metabolites of the phthalates di-ethyl phthalate (DEP), di-butyl phthalate (DBP), butylbenzyl phthalate (BBzP) and di-etylhexyl phthalate (DEHP) were measured in the urine of the children. Of 209 invited children, 110 (52%) participated. Urine samples were obtained from 83 of these. Urine levels of the BBzP metabolite monobenzyl phthalate (MBzP) was significantly higher in infants with PVC flooring in their bedrooms (p<0.007) and related to the body area of the infant. Levels of the DEHP metabolites MEHHP (p<0.01) and MEOHP (p<0.04) were higher in the two months old infants who were not exclusively breastfed when compared with breastfed children. The findings indicate that the use of soft PVC as flooring material may increase the human uptake of phthalates in infants. Urinary levels of phthalate metabolites during early life are associated to the use of PVC flooring in the bedroom, body area and the use of infant formula. © 2012 John Wiley & Sons A/S. (Less)

Use of personalized ventilation for improving health, comfort, and performance at high room temperature and humidity.

Abstract: UNLABELLED The effect of personalized ventilation (PV) on people's health, comfort, and performance in a warm and humid environment (26 and 28°C at 70% relative humidity) was studied and compared with their responses in a comfortable environment (23°C and 40% relative humidity). Thirty subjects participated in five 4-h experiments in a climate chamber. Under the conditions with PV, the subjects were able to control the rate and direction of the supplied personalized flow of clean air. Subjective responses were collected through questionnaires. During all exposures, the subjects were occupied with tasks used to assess their performance. Objective measures of tear film stability, concentration of stress biomarkers in saliva, and eye blinking rate were taken. Using PV significantly improved the perceived air quality (PAQ) and thermal sensation and decreased the intensity of Sick Building Syndrome (SBS) symptoms to those prevailing in a comfortable room environment without PV. Self-estimated and objectively measured performance was improved. Increasing the temperature and relative humidity, but not the use of PV, significantly decreased tear film quality and the concentration of salivary alpha-amylase, indicating lower mental arousal and alertness. The use of PV improved tear film stability as compared to that in a warm environment without PV. PRACTICAL IMPLICATIONS In practice, the supply of clean, cool, and less humid air by PV at each workstation will make it possible to raise room temperatures above the upper comfortable limit suggested in the present standards without adversely affecting the occupants' health [Sick Building Syndrome (SBS) symptoms], comfort (thermal and perceived air quality), and performance. This may lead to energy savings.

A randomized double‐blind crossover study of indoor air filtration and acute changes in cardiorespiratory health in a First Nations community

Abstract: Few studies have examined indoor air quality in First Nations communities and its impact on cardiorespiratory health. To address this need, we conducted a crossover study on a First Nations reserve in Manitoba, Canada, including 37 residents in 20 homes. Each home received an electrostatic air filter and a placebo filter for 1 week in random order, and lung function, blood pressure, and endothelial function measures were collected at the beginning and end of each week. Indoor air pollutants were monitored throughout the study period. Indoor PM2.5 decreased substantially during air filter weeks relative to placebo (mean difference: 37 μg/m3, 95% CI: 10, 64) but remained approximately five times greater than outdoor concentrations owing to a high prevalence of indoor smoking. On average, air filter use was associated with a 217-ml (95% CI: 23, 410) increase in forced expiratory volume in 1 s, a 7.9-mm Hg (95% CI: −17, 0.82) decrease in systolic blood pressure, and a 4.5-mm Hg (95% CI: −11, 2.4) decrease in diastolic blood pressure. Consistent inverse associations were also observed between indoor PM2.5 and lung function. In general, our findings suggest that reducing indoor PM2.5 may contribute to improved lung function in First Nations communities.

Ultrafine particle removal by residential heating, ventilating, and air-conditioning filters

Abstract: This work uses an in situ filter test method to measure the size-resolved removal efficiency of indoor-generated ultrafine particles (approximately 7–100 nm) for six new commercially available filters installed in a recirculating heating, ventilating, and air-conditioning (HVAC) system in an unoccupied test house. The fibrous HVAC filters were previously rated by the manufacturers according to ASHRAE Standard 52.2 and ranged from shallow (2.5 cm) fiberglass panel filters (MERV 4) to deep-bed (12.7 cm) electrostatically charged synthetic media filters (MERV 16). Measured removal efficiency ranged from 0 to 10% for most ultrafine particles (UFP) sizes with the lowest rated filters (MERV 4 and 6) to 60–80% for most UFP sizes with the highest rated filter (MERV 16). The deeper bed filters generally achieved higher removal efficiencies than the panel filters, while maintaining a low pressure drop and higher airflow rate in the operating HVAC system. Assuming constant efficiency, a modeling effort using these measured values for new filters and other inputs from real buildings shows that MERV 13–16 filters could reduce the indoor proportion of outdoor UFPs (in the absence of indoor sources) by as much as a factor of 2–3 in a typical single-family residence relative to the lowest efficiency filters, depending in part on particle size.

Numerical investigation of wind-induced airflow and interunit dispersion characteristics in multistory residential buildings.

Abstract: Compared with the buoyancy-dominated upward spread, the interunit dispersion of pollutants in wind-dominated conditions is expected to be more complex and multiple. The aim of this study is to investigate the wind-induced airflow and interunit pollutant dispersion in typical multistory residential buildings using computational fluid dynamics. The mathematical model used is the nonstandard k-e model incorporated with a two-layer near-wall modification, which is validated against experiments of previous investigators. Using tracer gas technique, the reentry of exhaust air from each distinct unit to other units on the same building, under different practical conditions, is quantified, and then, the possible dispersion routes are revealed. The units on the floor immediately below the source on the windward side, and vertically above it on the leeward side, where the reentry ratios are up to 4.8% and 14.9%, respectively, should be included on the high-infection list. It is also found that the presence of balconies results in a more turbulent near-wall flow field, which in turn significantly changes the reentry characteristics. Comparison of the dispersion characteristics of the slab-like building and the more complicated building in cross (#) floorplan concludes that distinctive infectious control measures should be implemented in these two types of buildings.

Indoor exposure to particulate matter and the incidence of acute lower respiratory infections among children: A birth cohort study in urban Bangladesh

Abstract: Approximately half of all children under two years of age in Bangladesh suffer from an acute lower respiratory infection (ALRI) each year. Exposure to indoor biomass smoke has been consistently associated with an increased risk of ALRI in young children. Our aim was to estimate the effect of indoor exposure to particulate matter (PM2.5 ) on the incidence of ALRI among children in a low-income urban community in Bangladesh. We followed 257 children through two years of age to determine their frequency of ALRI and measured the PM2.5 concentrations in their sleeping space. Poisson regression was used to estimate the association between ALRI and the number of hours per day that PM2.5 concentrations exceeded 100 mug/m(3) adjusting for known confounders. Each hour that PM2.5 concentrations exceeded 100 mug/m(3) was associated with a 7% increase in incidence of ALRI among children aged 0-11 months (adjusted incidence rate ratio (IRR) 1.07 95% CI 1.01-1.14) but not in children 12-23 months old (adjusted IRR 1.00 95% CI 0.92-1.09). Results from this study suggest that reducing indoor PM2.5 exposure could decrease the frequency of ALRI among infants the children at highest risk of death from these infections. (c) 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Mortality associated with exposure to carbon monoxide in WHO European Member States

Abstract: In closed environments, the concentration of carbon monoxide (CO) can easily rise to health-threatening levels. CO-related incidents are often caused by poor condition or inappropriate use of indoor combustion devices as well as structure fires but are also due to suicides. To evaluate the incidence of CO poisoning in Europe, national data on CO-related mortality and morbidity were compiled from Member States of the WHO European Region using a standardized data collection form. National data on CO poisoning were provided by 28 Member States. Within the maximum reporting period (1980-2008), a total of 140 490 CO-related deaths were reported (annual death rate of 2.2/100 000). The number of hospital admissions available from six countries was 31 473. Unintentional CO deaths accounted for 54.7% of the CO-related deaths (35.9%: unintentional inhalation; 18.8%: related to structure fires). The intentional deaths related to CO exposure account for 38.6% of all CO-related deaths (38.1%: suicides; 0.5%: homicides). CO exposure is preventable but causes a substantial amount of deaths in many European countries. More efficient measures and policies to prevent CO poisoning and better reporting of CO mortality are necessary.

Impact of a cleaner-burning cookstove intervention on blood pressure in Nicaraguan women

Abstract: Few studies have evaluated the cardiovascular-related effects of indoor biomass burning or the role of characteristics such as age and obesity status, in this relationship. We examined the impact of a cleaner-burning cookstove intervention on blood pressure among Nicaraguan women using an open fire at baseline; we also evaluated heterogeneity of the impact by subgroups of the population. We evaluated changes in systolic and diastolic blood pressure from baseline to post-intervention (range: 273-383 days) among 74 female cooks. We measured indoor fine particulate matter (PM(2.5); N = 25), indoor carbon monoxide (CO; N = 32), and personal CO (N = 30) concentrations. Large mean reductions in pollutant concentrations were observed for all pollutants; for example, indoor PM(2.5) was reduced 77% following the intervention. However, pollution distributions (baseline and post-intervention) were wide and overlapping. Although substantial reductions in blood pressure were not observed among the entire population, a 5.9 mmHg reduction [95% confidence interval (CI): -11.3, -0.4] in systolic blood pressure was observed among women aged 40 or more years and a 4.6 mmHg reduction (95% CI: -10.0, 0.8) was observed among obese women. Results from this study provide an indication that certain subgroups may be more likely to experience improvements in blood pressure following a cookstove intervention.

Pilot study of high‐performance air filtration for classroom applications

Abstract: A study was conducted to investigate the e! ectiveness of three air purification systems in reducing the exposure of children to air contaminants inside nine classrooms of three Southern California schools. Continuous and integrated measurements were conducted to monitor the indoor and outdoor concentrations of ultrafine particles (UFPs), fine and coarse particulate matter (PM2.5 and PM10, respectively), black carbon (BC), and volatile organic compounds. An heating, ventilating, and air conditioning (HVAC)-based high- performance panel filter (HP-PF), a register-based air purifier (RS), and a stand-alone air cleaning system (SA) were tested alone and in di! erent combinations for their ability to remove the monitored pollutants. The combination of a RS and a HP-PF was the most e! ective solution for lowering the indoor concentrations of BC, UFPs, and PM2.5, with study average reductions between 87% and 96%. When using the HP-PF alone, reductions close to 90% were also achieved. In all cases, air quality conditions were improved substantially with respect to the corresponding baseline (preexisting) conditions. Data on the performance of the gas-absorbing media included in the RS and SA unit were inconclusive, and their e! ectiveness, lifetime, costs, and benefits must be further assessed before conclusions and recommendations can be made.

The risk of airborne cross-infection in a room with vertical low-velocity ventilation

Abstract: UNLABELLED Downward flow ventilation systems are one of the most recommended ventilation strategies when contaminants in rooms must be removed and people must be protected from the risk of airborne cross-infection. This study is based on experimental tests carried out in a room with downward flow ventilation. Two breathing thermal manikins are placed in a room face to face. One manikin's breathing is considered to be the contaminated source to simulate a risky situation with airborne cross-infection. The position of the manikins in relation to the diffuser and the location of diffuser in the room as well as the distance between the manikins are being changed to observe the influence of these factors on the personal exposure of the target manikin. The results show that the DWF in different situations often is unable to penetrate the microenvironment generated by the manikins. The downward ventilation system can give an unexpected high level of contaminant exposure of the target manikin, when the distance between the manikins is reduced. PRACTICAL IMPLICATIONS Several guidelines recommend the downward ventilation system to reduce the risk of cross-infection between people in hospital rooms. This study shows that this recommendation should be taken into careful consideration. It is important to be aware of people position, position to other thermal loads in the room, and especially be aware of the distance between people if the exposure to the exhaled contaminants wants to be reduced.

Analysis of selected phthalates in Canadian indoor dust collected using household vacuum and standardized sampling techniques.

Abstract: Phthalates have been used extensively as plasticizers to improve the flexibility of polymers, and they also have found many industrial applications. They are ubiquitous in the environment and have been detected in a variety of environmental and biological matrices. The goal of this study was to develop a method for the determination of 17 phthalate esters in house dust. This method involved sonication extraction, sample cleanup using solid phase extraction, and isotope dilution GC/MS/MS analysis. Method detection limits (MDLs) and recoveries ranged from 0.04 to 2.93 μg/g and from 84 to 117%, respectively. The method was applied to the analysis of phthalates in 38 paired household vacuum samples (HD) and fresh dust (FD) samples. HD and FD samples compared well for the majority of phthalates detected in house dust. Data obtained from 126 household dust samples confirmed the historical widespread use of bis(2-ethylhexyl) phthalate (DEHP), with a concentration range of 36 μg/g to 3840 μg/g. Dibutyl phthalate (DBP), benzyl butyl phthalate (BzBP), diisononyl phthalate (DINP), and diisodecyl phthalate (DIDP) were also found in most samples at relatively high concentrations. Another important phthalate, diisobutyl phthalate (DIBP), was detected at a frequency of 98.4% with concentrations ranging from below its MDL of 0.51 μg/g to 69 μg/g.

People who live in a cold climate: thermal adaptation differences based on availability of heating

Abstract: Are there differences in thermal adaptation to cold indoor environments between people who are used to living in heating and non-heating regions in China? To answer this question, we measured thermal perceptions and physiological responses of young men from Beijing (where there are indoor space heating facilities in winter) and Shanghai (where there are not indoor space heating facilities in winter) during exposures to cold Subjects were exposed to 12°C, 14°C, 16°C, 18°C, 20°C for 1 h Subjects from Beijing complained of greater cold discomfort and demonstrated poorer physiological acclimatization to cold indoor environments than those from Shanghai These findings indicate that people's chronic indoor thermal experience might be an important determinant of thermal adaptation

Phthalates in indoor dust in Kuwait: implications for non‐dietary human exposure

Abstract: Phthalates are semivolatile organic compounds with a ubiquitous environmental distribution. Their presence in indoor environments is linked to their use in a variety of consumer products such as children's toys, cosmetics, food packaging, flexible PVC flooring among others. The goal of this study was to investigate the occurrence and concentration of phthalates in dust from homes in Kuwait and to assess non-dietary human exposure to these phthalates. Dust samples were randomly collected from 21 homes and analyzed for eight phthalates. The concentrations of total phthalates were log normally distributed and ranged from 470 to 7800 μg/g. Five phthalates [Di(2-ethylhexyl) phthalate (DEHP), Di-n-octyl phthalate (DnOP), Di-n-butyl phthalate (DBP), Benzyl butyl phthalate (BzBP), and Dicyclohexyl phthalate (DcHP)] were routinely detected. The major phthalate compound was DEHP at a geometric mean concentration of 1704 μg/g (median, 2256 μg/g) accounting for 92% of the total phthalates measured. Using the measured concentrations and estimates of dust ingestion rates for children and adults, estimated human non-dietary exposure based on median phthalate concentrations ranged from 938 ng/kg-bd/day for adults to 13362 ng/kg-bd/day for toddlers. The difference in exposure estimates between children and adults in this study supports previous reports that children are at greater risk from pollutants that accumulate indoors.

Submicrometer particle removal indoors by a novel electrostatic precipitator with high clean air delivery rate, low ozone emissions, and carbon fiber ionizer.

Abstract: A novel positive-polarity electrostatic precipitator (ESP) was developed using an ionization stage (0.4 × 0.4 × 0.14 m(3) ) with 16 carbon fiber ionizers in each channel and a collection stage (0.4 × 0.4 × 0.21 m(3) ) with parallel metallic plates. The single-pass collection efficiency and clean air delivery rate (CADR) were measured by standard tests using KCl particles in 0.25-0.35 μm. Performance was determined using the Deutsch equation and established diffusion and field charging theories and also compared with the commercialized HEPA filter-type air cleaner. Experimental results showed that the single-pass collection efficiency of the ESP ranged from 50 to 95% and decreased with the flow rate (10-20 m(3) /min), but increased with the voltage applied to the ionizers (6 to 8 kV) and collection plates (-5 to -7 kV). The ESP with 18 m(3) /min achieved a CADR of 12.1 m(3) /min with a voltage of 8 kV applied to the ionization stage and with a voltage of -6 kV applied to the collection stage. The concentration of ozone in the test chamber (30.4 m(3) ), a maximum value of 5.4 ppb over 12 h of continuous operation, was much lower than the current indoor regulation (50 ppb).

Proinflammatory effects of cookstove emissions on human bronchial epithelial cells.

Abstract: Approximately half the world’s population uses biomass fuel for indoor cooking and heating. This form of combustion typically occurs in open fires or primitive stoves. Human exposure to emissions from indoor biomass combustion is a global health concern, causing an estimated 1.5 million premature deaths each year. Many ‘improved’ stoves have been developed to address this concern; however, studies that examine exposure-response with cleaner-burning, more efficient stoves are few. The objective of this research was to evaluate the effects of traditional and cleaner burning stove emissions on an established model of the bronchial epithelium. We exposed well-differentiated, normal human bronchial epithelial (NHBE) cells to emissions from a single biomass combustion event using either a traditional three-stone fire or one of two energy-efficient stoves. Air-liquid interface cultures were exposed using a novel, aerosol-to-cell deposition system. Cellular expression of a panel of three pro-inflammatory markers was evaluated at 1 and 24 hours following exposure. Cells exposed to emissions from the cleaner burning stoves generated significantly fewer amounts of pro-inflammatory markers than cells exposed to emissions from a traditional, three stone fire. Particulate matter emissions from each cookstove were substantially different, with the three-stone fire producing the largest concentrations of particles (by both number and mass). This study supports emerging evidence that more efficient cookstoves have the potential to reduce respiratory inflammation in settings where solid fuel combustion is used to meet basic domestic needs.

Co-occupant's exposure to exhaled pollutants with two types of personalized ventilation strategies under mixing and displacement ventilation systems.

Abstract: Personalized ventilation (PV) system in conjunction with total ventilation system can provide cleaner inhaled air for the user. Concerns still exist about whether the normally protecting PV device, on the other hand, facilitates the dispersion of infectious agents generated by its user. In this article, two types of PV systems with upward supplied fresh air, namely a chair-based PV and one kind of desk-mounted PV systems, when combined with mixing ventilation (MV) and displacement ventilation (DV) systems, are investigated using simulation method with regard to their impacts on co-occupant's exposure to the exhaled droplet nuclei generated by the infected PV user. Simulation results of tracer gas and particles with aerodynamic diameter of 1, 5, and 10 μm from exhaled air show that, when only the infected person uses a PV, the different PV air supplying directions present very different impacts on the co-occupant's intake under DV, while no apparent differences can be observed under MV. The findings demonstrate that better inhaled air quality can always be achieved under DV when the adopted PV system can deliver conditioned fresh air in the same direction with the mainly upward airflow patterns of DV.

Dose-response relationships between mouse allergen exposure and asthma morbidity among urban children and adolescents

Abstract: Home mouse allergen exposure is associated with asthma morbidity, but little is known about the shape of the dose-response relationship or the relevance of location of exposure within the home. Asthma outcome and allergen exposure data were collected every 3 months for 1 year in 150 urban children with asthma. Participants were stratified by mouse sensitization, and relationships between continuous measures of mouse allergen exposure and outcomes of interest were analyzed. Every tenfold increase in the bed mouse allergen level was associated with an 87% increase in the odds of any asthma-related health care use among mouse-sensitized [Odds Ratio (95% CI): 1.87 (1.21-2.88)], but not non-mouse-sensitized participants. Similar relationships were observed for emergency department visit and unscheduled doctor visit among mouse-sensitized participants. Kitchen floor and bedroom air mouse allergen concentrations were also associated with greater odds of asthma-related healthcare utilization; however, the magnitude of the association was less than that observed for bed mouse allergen concentrations. In this population of urban children with asthma, there is a linear dose-response relationship between mouse allergen concentrations and asthma morbidity among mouse-sensitized asthmatics. Bed and bedroom air mouse allergen exposure compartments may have a greater impact on asthma morbidity than other compartments.

On the suitability of steady RANS CFD for forced mixing ventilation at transitional slot Reynolds numbers

Abstract: Accurate prediction of ventilation flow is of primary importance for designing a healthy, comfortable and energy-efficient indoor environment. Since the 1970s, the use of computational fluid dynamics (CFD) has increased tremendously and nowadays it is one of the primary methods to assess ventilation flow in buildings. The most commonly used numerical approach consists of solving the steady Reynolds-averaged Navier-Stokes (RANS) equations with a turbulence model to provide closure. This paper presents a detailed validation study of steady RANS for isothermal forced mixing ventilation of a cubical enclosure driven by a transitional wall jet. The validation is performed using particle image velocimetry (PIV) measurements for slot Reynolds numbers of 1,000 and 2,500. Results obtained with the renormalization group (RNG) k-e model, a low-Reynolds k-e model, the shear stress transport (SST) k-ω model and a Reynolds stress model (RSM) are compared with detailed experimental data. In general, the RNG k-e model shows the weakest performance, whereas the low-Re k-e model shows the best agreement with the measurements. In addition, the influence of the turbulence model on the predicted air exchange efficiency in the cubical enclosure is analyzed, indicating differences up to 44% for this particular case.

Bacterial communities in commercial aircraft high-efficiency particulate air (HEPA) filters assessed by PhyloChip analysis.

Abstract: Air travel can rapidly transport infectious diseases globally. To facilitate the design of biosensors for infectious organisms in commercial aircraft, we characterized bacterial diversity in aircraft air. Samples from 61 aircraft high-efficiency particulate air (HEPA) filters were analyzed with a custom microarray of 16S rRNA gene sequences (PhyloChip), representing bacterial lineages. A total of 606 subfamilies from 41 phyla were detected. The most abundant bacterial subfamilies included bacteria associated with humans, especially skin, gastrointestinal and respiratory tracts, and with water and soil habitats. Operational taxonomic units that contain important human pathogens as well as their close, more benign relatives were detected. When compared to 43 samples of urban outdoor air, aircraft samples differed in composition, with higher relative abundance of Firmicutes and Gammaproteobacteria lineages in aircraft samples, and higher relative abundance of Actinobacteria and Betaproteobacteria lineages in outdoor air samples. In addition, aircraft and outdoor air samples differed in the incidence of taxa containing human pathogens. Overall, these results demonstrate that HEPA filter samples can be used to deeply characterize bacterial diversity in aircraft air and suggest that the presence of close relatives of certain pathogens must be taken into account in probe design for aircraft biosensors. Practical Implications A biosensor that could be deployed in commercial aircraft would be required to function at an extremely low false alarm rate, making an understanding of microbial background important. This study reveals a diverse bacterial background present on aircraft, including bacteria closely related to pathogens of public health concern. Furthermore, this aircraft background is different from outdoor air, suggesting different probes may be needed to detect airborne contaminants to achieve minimal false alarm rates. This study also indicates that aircraft HEPA filters could be used with other molecular techniques to further characterize background bacteria and in investigations in the wake of a disease outbreak.

Are rocket mud stoves associated with lower indoor carbon monoxide and personal exposure in rural Kenya

Abstract: Household use of biomass fuels is a major source of indoor air pollution and poor health in developing countries. We conducted a cross-sectional investigation in rural Kenya to assess household air pollution in homes with traditional three-stone stove and rocket mud stove (RMS), a low-cost unvented wood stove. We conducted continuous measurements of kitchen carbon monoxide (CO) concentrations and personal exposures in 102 households. Median 48-hour kitchen and personal CO concentrations were 7.3 ppm and 6.5 ppm respectively for three-stone stoves, while the corresponding concentrations for RMS were 5.8 ppm and 4.4 ppm. After adjusting for kitchen location, ventilation, socio-economic status and fuel moisture content, the use of RMS was associated with 33% lower levels of kitchen CO (95% Confidence Interval [CI]: 64.4%, - 25.1%) and 42% lower levels of personal CO (95% CI: 66.0%, - 1.1%) as compared to three-stone stoves. Differences in CO concentrations by stove type were more pronounced when averaged over the cooking periods, although they were attenuated after adjusting for confounding. In conclusion, RMS appear to lower kitchen and personal CO concentrations compared to the traditional three-stone stoves but overall, the CO concentrations remain high. © 2012 John Wiley & Sons A/S.

Coarse particulate matter and airborne endotoxin within wood stove homes.

Abstract: Emissions from indoor biomass burning are a major public health concern in developing areas of the world. Less is known about indoor air quality, particularly airborne endotoxin, in homes burning biomass fuel in residential wood stoves in higher income countries. A filter-based sampler was used to evaluate wintertime indoor coarse particulate matter (PM₁₀₋₂.₅) and airborne endotoxin (EU/m³, EU/mg) concentrations in 50 homes using wood stoves as their primary source of heat in western Montana. We investigated number of residents, number of pets, dampness (humidity), and frequency of wood stove usage as potential predictors of indoor airborne endotoxin concentrations. Two 48-h sampling events per home revealed a mean winter PM₁₀₋₂.₅ concentration (± s.d.) of 12.9 (± 8.6) μg/m³, while PM₂.₅ concentrations averaged 32.3 (± 32.6) μg/m³. Endotoxin concentrations measured from PM₁₀₋₂.₅ filter samples were 9.2 (± 12.4) EU/m³ and 1010 (± 1524) EU/mg. PM₁₀₋₂.₅ and PM₂.₅ were significantly correlated in wood stove homes (r = 0.36, P < 0.05). The presence of pets in the homes was associated with PM₁₀₋₂.₅ but not with endotoxin concentrations. Importantly, none of the other measured home characteristics was a strong predictor of airborne endotoxin, including frequency of residential wood stove usage.

Chimney stoves modestly improved Indoor Air Quality measurements compared with traditional open fire stoves: results from a small-scale intervention study in rural Peru

Abstract: Nearly half of the world's population depends on biomass fuels to meet domestic energy needs, producing high levels of pollutants responsible for substantial morbidity and mortality. We compare carbon monoxide (CO) and particulate matter (PM2.5) exposures and kitchen concentrations in households with study-promoted intervention (OPTIMA-improved stoves and control stoves) in San Marcos Province, Cajamarca Region, Peru. We determined 48-h indoor air concentration levels of CO and PM2.5 in 93 kitchen environments and personal exposure, after OPTIMA-improved stoves had been installed for an average of 7 months. PM2.5 and CO measurements did not differ significantly between OPTIMA-improved stoves and control stoves. Although not statistically significant, a post hoc stratification of OPTIMA-improved stoves by level of performance revealed mean PM2.5 and CO levels of fully functional OPTIMA-improved stoves were 28% lower (n = 20, PM2.5, 136 μg/m(3) 95% CI 54-217) and 45% lower (n = 25, CO, 3.2 ppm, 95% CI 1.5-4.9) in the kitchen environment compared with the control stoves (n = 34, PM2.5, 189 μg/m(3), 95% CI 116-261; n = 44, CO, 5.8 ppm, 95% CI 3.3-8.2). Likewise, although not statistically significant, personal exposures for OPTIMA-improved stoves were 43% and 17% lower for PM2.5 (n = 23) and CO (n = 25), respectively. Stove maintenance and functionality level are factors worthy of consideration for future evaluations of stove interventions.

Endotoxin, extracellular polysaccharides, and β(1-3)-glucan concentrations in dust and their determinants in four European birth cohorts: results from the HITEA project.

Abstract: UNLABELLED Early-life exposure to microbial agents may play a protective role in asthma and allergies development. Geographical differences in the prevalence of these diseases exist, but the differences in early-life indoor microbial agent levels and their determinants have been hardly studied. We aimed to describe the early-life levels of endotoxin, extracellular polysaccharides (EPS), and β(1-3)-glucans in living room dust of four geographically spread European birth cohorts (LISA in Germany, PIAMA in the Netherlands, INMA in Spain, and LUKAS2 in Finland) and to assess their determinants. A total of 1572 dust samples from living rooms of participants were analyzed for endotoxin, Penicillium/Aspergillus EPS, and β(1-3)-glucans. Information on potential determinants was obtained through questionnaires. Concentrations of endotoxin, EPS, and β(1-3)-glucans were different across cohorts. Concentrations of endotoxin and EPS were respectively lower and higher in INMA than in other cohorts, while glucans were higher in LUKAS2. Season of sampling, dog ownership, dampness, and the number of people living at home were significantly associated with concentrations of at least one microbial agent, with heterogeneity of effect estimates of the determinants across cohorts. In conclusion, both early-life microbial exposure levels and exposure determinants differ across cohorts derived from diverse European countries. PRACTICAL IMPLICATIONS This study adds evidence of variability in the levels of indoor endotoxin, extracellular polysaccharide, and β(1-3)-glucans across four geographically spread European regions. Furthermore, we observed heterogeneity across regions in the effect of exposure determinants. We hypothesize that the variations observed in our study may play a role in the differences in asthma and allergies prevalences across countries.

Isolation of Aspergillus fumigatus from sputum is associated with elevated airborne levels in homes of patients with asthma.

Abstract: Indoor bioaerosols, such as mold spores, have been associated with respiratory symptoms in patients with asthma; however, dose-response relationships and guidelines on acceptable levels are lacking. Furthermore, a causal link between mold exposure and respiratory infections or asthma remains to be established. The aim of this study was to determine indoor concentrations of Aspergillus fumigatus and a subset of clinically relevant fungi in homes of people with asthma, in relation to markers of airways colonization and sensitization. Air and dust samples were collected from the living room of 58 properties. Fungal concentrations were quantified using mold-specific quantitative PCR and compared with traditional microscopic analysis of air samples. Isolation of A. fumigatus from sputum was associated with higher airborne concentrations of the fungus in patient homes (P = 0.04), and a similar trend was shown with Aspergillus/Penicillium-type concentrations analyzed by microscopy (P = 0.058). No association was found between airborne levels of A. fumigatus and sensitization to this fungus, or dustborne levels of A. fumigatus and either isolation from sputum or sensitization. The results of this study suggest that the home environment should be considered as a potential source of fungal exposure, and elevated home levels may predispose people with asthma to airways colonization.

Filtration effectiveness of HVAC systems at near-roadway schools.

Abstract: Concern for the exposure of children attending schools located near busy roadways to toxic, traffic-related air pollutants has raised questions regarding the environmental benefits of advanced heating, ventilation, and air-conditioning (HVAC) filtration systems for near-road pollution. Levels of black carbon and gaseous pollutants were measured at three indoor classroom sites and at seven outdoor monitoring sites at Las Vegas schools. Initial HVAC filtration systems effected a 31–66% reduction in black carbon particle concentrations inside three schools compared with ambient air concentrations. After improved filtration systems were installed, black carbon particle concentrations were reduced by 74–97% inside three classrooms relative to ambient air concentrations. Average black carbon particle concentrations inside the schools with improved filtration systems were lower than typical ambient Las Vegas concentrations by 49–96%. Gaseous pollutants were higher indoors than outdoors. The higher indoor concentrations most likely originated at least partially from indoor sources, which were not targeted as part of this intervention.