Numerical investigation of airflow pattern and particulate matter transport in naturally ventilated multi-room buildings

This study reports on a numerical investigation of transport behavior of indoor airflow and size-dependent particulate matter (PM) in multi-room buildings. An indoor size-dependent PM transport approach, combining the Eulerian large-eddy simulation of turbulent flow with the Lagrangian particle trajectory tracking, was developed to investigate indoor airflow pattern and PM1/PM2.5/PM10 removal efficiency in naturally ventilated multi-room buildings. A displacement ventilation with a measured indoor PM10 profile in Taipei Metropolis as the initial condition was carried out to characterize spatial and temporal variations of indoor PM1/PM2.5/PM10 removal behavior. The effects of indoor airflow pattern on particle transport mechanisms, e.g., deposition, suspension, migration and escape, were analyzed. Two comparison scenarios, which considered the effects of no indoor partition and different air change rate, respectively, were also conducted. In comparison with the effectiveness of PM1/PM2.5/PM10 removal, the simulated results showed that coarse particles were easier to be removed out of the building than fine particles. Natural ventilation was not an effective way to remove fine particles such as PM1 and PM2.5 in a multi-room building. Indoor partitions can impede 12% of the mean streamwise velocities and significantly increase 30-50% turbulence intensities. However, indoor partitions increased particle deposition and decreased particle escape. As a result of the two opposite particle removal mechanisms, i.e., deposition and escape, the impact of indoor partitions on PM1/PM2.5/PM10 removal behavior was not as significant as the results of airflow velocities. PRACTICAL IMPLICATIONS: This work developed a computational fluid dynamics technique to investigate indoor airflow patterns and PM1/PM2.5/PM10 removal ability in ventilated multi-room buildings. The results of this paper can help to identify adequate PM1/PM2.5/PM10 cleaning procedure and provide useful size-dependent PM control strategy in multi-room buildings.     

Indoor and outdoor PM2.5 and PM10 concentrations in the air during a dust storm

Asian dust storms (ADS) originating from the arid deserts of Mongolia and China are a well-known springtime meteorological phenomenon throughout East Asia. The ventilation systems in office utilize air from outside and therefore it is necessary to understand how these dust storms affect the concentrations of PM_2.5 and PM₁₀ in both the indoor and outdoor air. We measured dust storm pollution particles in an office building using a direct-reading instrument (PC-2 Quartz Crystal Microbalance, QCM) that measured particle size and concentration every 10 min for 1 h, three times a day. A three-fold increase in the concentrations of PM_2.5 and PM₁₀ in the indoor and outdoor air was recorded during the dust storms. After adjusting for other covariates, autoregression models indicated that PM_2.5 and PM₁₀ in the indoor air increased significantly (21.7 μg/m³ and 23.0 μg/m³ respectively) during dust storms. The ventilation systems in high-rise buildings utilize air from outside and therefore the indoor concentrations of fine and coarse particles in the air inside the buildings are significantly affected by outside air pollutants, especially during dust storms.     

Variation in indoor particle number and PM2.5 concentrations in a radio station surrounded by busy roads before and after an upgrade of the HVAC system

Indoor particle number and PM_2.5 concentrations were investigated in a radio station surrounded by busy roads. Two extensive field measurement campaigns were conducted to determine the critical parameters affecting indoor air quality. The results indicated that indoor particle number and PM_2.5 concentrations were governed by outdoor air, and were significantly affected by the location of air intake and design of HVAC system. Prior to the upgrade of the HVAC system and relocation of the air intake, the indoor median particle number concentration was 7.4×10³ particles/cm³ and the median PM_2.5 concentration was 7 μg/m³. After the relocation of air intake and the redesign of the HVAC system, the indoor particle number concentration was between 2.3×10³ and 3.4×10³ particles/cm³, with a median value of 2.7×10³ particles/cm³, and the indoor PM_2.5 concentration was in the range of 3–5 μg/m³, with a median value of 4 μg/m³. By relocating the air intake of the HVAC, the outdoor particle number and PM_2.5 concentrations near the air intake were reduced by 35% and 55%, respectively. In addition, with the relocation of air intake and the redesign of the HVAC system, the particle number penetration rate was reduced from 42% to 14%, and the overall filtration efficiency of the HVAC system (relocation of air intake, pre-filter, AHU and particle losses in the air duct) increased from 58% to 86%. For PM_2.5, the penetration rate after the upgrade was approximately 18% and the overall filtration efficiency was 82%. This study demonstrates that by using a comprehensive approach, including the assessment of outdoor conditions and characterisation of ventilation and filtration parameters, satisfactory indoor air quality can be achieved, even for those indoor environments facing challenging outdoor air conditions.     

Lessons learned from a woodstove changeout on the Nez Perce Reservation

A woodstove changeout program was conducted within 16 homes on the Nez Perce Reservation in Idaho to evaluate the effectiveness of a woodstove changeout in improving indoor air quality. PM_2.5 samples were collected within the common area (rooms where the stoves were located) of the homes both before and after the installation of cleaner burning EPA-certified stoves. During the pre- and post-changeout sampling, indoor PM_2.5 mass, Organic Carbon (OC), Elemental Carbon (EC), and chemical markers of woodsmoke (including levoglucosan) were measured.Sampling results from this study showed that indoor air quality was improved in 10 of the 16 homes following the woodstove changeout and educational training program. Five homes had increased indoor PM_2.5 concentrations following the changeout, while one home did not have final PM_2.5 results for comparison. The median pre-changeout PM_2.5 mass (as measured by TSI DustTraks) was 39.2 μg/m³, with a median post-changeout concentration of 19.0 μg/m³. This resulted in an overall 52% reduction in median indoor PM_2.5, a 36% reduction in mean indoor PM_2.5 and a 60% reduction in PM_2.5 spikes when the old stoves were replaced with EPA-certified stoves. Another significant finding of the project was that targeted education and outreach is a critical component of the overall success of the program. Effective messaging to homeowners on proper use of their new stove is a necessary task of a woodstove changeout.     

Exposure to fine particulate matter in ten night clubs in Athens Greece: Studying the effect of ventilation, cigarette smoking and resuspension

The aim of the present work is to study the occupants' exposure to fine particulate concentrations in ten nightclubs (NCs) in Athens, Greece. Measurements of PM₁ and PM_2.5 were made in the outdoor and indoor environment of each NC. The average indoor PM₁ and PM_2.5 concentrations were found to be 181.77 μg m^− 3 and 454.08 μg m^− 3 respectively, while the corresponding outdoor values were 11.04 μg m^− 3 and 32.19 μg m^− 3. Ventilation and resuspension rates were estimated through consecutive numerical experiments with an indoor air quality model and were found to be remarkably lower than the minimum values recommended by national standards. The relative effects of the ventilation and smoking on the occupants' exposures were examined using multiple regression techniques. It was found that given the low ventilation rates, the effect of smoking as well as the occupancy is of the highest importance. Numerical evaluations showed that if the ventilation rates were at the minimum values set by national standards, then the indoor exposures would be reduced at the 70% of the present exposure values.     

Interpretation of the variability of levels of regional background aerosols in the Western Mediterranean

Results on interpretation of the variability of regional background PM levels in the Western Mediterranean basin (WMB) are presented. Mean PM levels recorded at Montseny, MSY (North-Eastern Spain) in the 2002-2007 period reached 17, 13 and 11 µg/m³ of PM₁₀, PM_2.5 and PM₁, respectively.The daily evolution of PM levels is regulated by the breeze circulation (mountain and sea breezes). PM levels are lower at the rural sites at night owing to the nocturnal drainage flows and to the lowering of the mixing layer height below the MSY high. These nocturnal low levels allowed us to estimate the continental background PM levels. At midday, the atmospheric pollutants accumulated in the pre-coastal depression are transported upwards by the breeze, increasing PM levels.Maximum PM₁₀ levels were recorded in summer, and February-March and November, and minimum values in the rest of the year coinciding with the highest frequency of Atlantic advection. PM peak episodes attributed to Saharan dust outbreaks were recorded in summer and February-March. In addition, anticyclonic situations (February-March and November) may impact in elevated rural areas by increasing hourly levels of PM₁ up to 75 µg/m³. This scenario induces the stagnation of pollutants in the pre-coastal depression. Solar radiation activates mountain winds, transporting polluted air masses from the valleys to elevated areas resulting in an increase of fine PM levels in areas outside the boundary layer.A significant decrease in PM annual means (40% and 34% for the entire monitoring period, 7 µgPM₁₀/m³ and 5 µgPM_2.5/m³) was recorded at MSY between 2002 and 2007. There appears to be no single cause behind these trends. This could partially be ascribed to the varying frequency and intensity of Saharan dust episodes, but also to large-scale meteorological processes or cycles, and/or to local or meso-scale processes such as nearby anthropogenic emission sources.     

Particulate matter and gaseous pollutants in residences in Antwerp, Belgium

This comprehensive study, a first in Flanders, Belgium, aimed at characterizing the residential indoor air quality of subgroups that took part in the European Community Respiratory Health Survey (ECRHS I—1991 and ECHRS II—1996) questionnaire-based asthma and related illnesses studies. This pilot study aimed at the evaluation of particulate matter and various inorganic gaseous compounds in residences in Antwerp. In addition personal exposure to the gaseous compounds of one individual per residence was assessed. The main objective was to obtain some base-line pollutant levels and compare these with studies performed in other cities, to estimate the indoor air quality in residences in Antwerp. Correlations between the various pollutant levels, indoor:outdoor ratios and the micro-environments of each residence were investigated. This paper presents results on indoor and ambient PM₁, PM_2.5 and PM₁₀ mass concentrations, its elemental composition in terms of K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br, Pb, Al, Si, S and Cl and the water-soluble ionic concentrations in terms of SO₄²⁻, NO₃²⁻, Cl⁻, NH₄⁺ K⁺, Ca²⁺. In addition, indoor, ambient and personal exposure levels of the gases NO₂, SO₂, and O₃ were determined. Elevated indoor:outdoor ratios were found for NO₂ in residences containing gas stoves. In smoker's houses increased PM concentrations of 58 and 43% were found for the fine and coarse fractions respectively. Contrary to the fact that all I/O ratios of the registered elements in each individual house were significantly correlated to each other, no correlation could be established between the I/O ratios of the different houses, thus indicating a unique micro-environment for each residence. Linear relationships between the particulate matter elemental composition, SO₂ and O₃ levels indoors and outdoors could be established. No linear relationships between indoor and outdoor NO₂ and particulate mass concentrations were found.     

Role of Saharan dust in the relationship between particulate matter and short-term daily mortality among the elderly in Madrid (Spain)

Background

Saharan dust outbreaks are a common phenomenon in the Madrid atmosphere. The current Directive 2008/50 CE governing air quality in European cities, draws no distinction between which particulate matter (PM₁₀, PM_2.5 or PM_10-2.5) would be the best indicator on days with/without Saharan dust intrusions. This study sought to identify the role played by Saharan dust in the relationship between particulate matter (PM₁₀, PM_2.5 and PM_10-2.5) concentrations and daily mortality among the elderly in the city of Madrid.

Methods

We conducted an ecological longitudinal time-series study on daily mortality among the over-75 age group, from 2003 to 2005. Poisson regression models were constructed for days with and without Saharan dust intrusions. The following causes of daily mortality were analysed: total organic causes except accidents (International Classification of Diseases-10th revision (ICD-10): A00-R99); circulatory causes (ICD-10: I00-I99); and respiratory causes (ICD-10: J00-J99). Daily mean PM₁₀, PM_2.5 and PM_10-2.5 levels were used as independent variables. Control variables were: other ambient pollutants (chemical, biotic and acoustic); trend; seasonalities; influenza epidemics; and autocorrelations between mortality series.

Results

While daily mean PM_2.5 concentrations in Madrid displayed a significant statistical association with daily mortality for all the above causes on days without Saharan dust intrusions, this association was not in evidence for PM₁₀ or PM_10-2.5 in the multivariate models. The relative risks (RRs) obtained for an increase of 10 μg/m³ in PM_2.5 concentrations were: 1.023 (1.010-1.036) for total organic causes; 1.033 (1.031-1.035) for circulatory causes; and 1.032 (1.004-1.059) for respiratory causes. On Saharan dust days, a significant statistical association was detected between PM₁₀ (though not PM_2.5 or PM_10-2.5) and mortality for all 3 causes analysed, with RRs statistically similar to those reported for PM_2.5.

Conclusions

The best air quality indicators for evaluating the short-term health effects of particulate matter in Madrid are therefore PM₁₀ concentrations on days with, and PM_2.5 concentrations on days without Saharan dust outbreaks. This fact should be taken into account in a European Directive regulating ambient air quality in almost all countries in the Mediterranean area.     

Size distribution and chemical composition of airborne particles in south-eastern Finland during different seasons and wildfire episodes in 2006

The inorganic main elements, trace elements and PAHs were determined from selected PM₁, PM_2.5 and PM₁₀ samples collected at the Nordic background station in Virolahti during different seasons and during the wildfire episodes in 2006. Submicron particles are those most harmful to human beings, as they are able to penetrate deep into the human respiratory system and may cause severe health effects. About 70-80%, of the toxic trace elements, like lead, cadmium, arsenic and nickel, as well as PAH compounds, were found in particles smaller than 1 µm. Furthermore, the main part of the copper, zinc, and vanadium was associated with submicron particles. In practice, all the PAHs found in PM₁₀ were actually in PM_2.5. For PAHs and trace elements, it is more beneficial to analyse the PM_2.5 or even the PM₁ fraction instead of PM₁₀, because exclusion of the large particles reduces the need for sample cleaning to minimize the matrix effects during the analysis. During the wildfire episodes, the concentrations of particles smaller than 2.5 µm, as well as those of submicron particles, increased, and also the ratio PM₁/PM₁₀ increased to about 50%. On the fire days, the mean potassium concentration was higher in all particle fractions, but ammonium and nitrate concentrations rose only in particles smaller than 1.0 µm. PAH concentrations rose even to the same level as in winter.     

Factors influencing relationships between personal and ambient concentrations of gaseous and particulate pollutants

Previous exposure studies have shown considerable inter-subject variability in personal-ambient associations. This paper investigates exposure factors that may be responsible for inter-subject variability in these personal-ambient associations. The personal and ambient data used in this paper were collected as part of a personal exposure study conducted in Boston, MA, during 1999-2000. This study was one of a group of personal exposure panel studies funded by the U.S. Environmental Protection Agency's National Exposure Research Laboratory to address areas of exposure assessment warranting further study, particularly associations between personal exposures and ambient concentrations of particulate matter and gaseous co-pollutants. Twenty-four-hour integrated personal, home indoor, home outdoor and ambient sulfate, elemental carbon (EC), PM_2.5, ozone (O₃), nitrogen dioxide (NO₂) and sulfur dioxide were measured simultaneously each day. Fifteen homes in the Boston area were measured for 7 days during winter and summer. A previous paper explored the associations between personal-indoor, personal-outdoor, personal-ambient, indoor-outdoor, indoor-ambient and outdoor-ambient PM_2.5, sulfate and EC concentrations. For the current paper, factors that may affect personal exposures were investigated, while controlling for ambient concentrations. The data were analyzed using mixed effects regression models. Overall personal-ambient associations were strong for sulfate during winter (p < 0.0001) and summer (p < 0.0001) and PM_2.5 during summer (p < 0.0001). The personal-ambient mixed model slope for PM_2.5 during winter but was not significant at p = 0.10. Personal exposures to most pollutants, with the exception of NO₂, increased with ventilation and time spent outdoors. An opposite pattern was found for NO₂ likely due to gas stoves. Personal exposures to PM_2.5 and to traffic-related pollutants, EC and NO₂, were higher for those individuals living close to a major road. Both personal and indoor sulfate and PM_2.5 concentrations were higher for homes using humidifiers. The impact of outdoor sources on personal and indoor concentrations increased with ventilation, whereas an opposite effect was observed for the impact of indoor sources.     

Temporal variation of nitro-polycyclic aromatic hydrocarbons in PM10 and PM2.5 collected in Northern Mexico City

With the aim to determine the presence of individual nitro-PAH contained in particles in the atmosphere of Mexico City, a monitoring campaign for particulate matter (PM₁₀ and PM_2.5) was carried out in Northern Mexico City, from April 2006 to February 2007. The PM₁₀ annual median concentration was 65.2 μg m^− 3 associated to 7.6 μg m^− 3 of solvent-extractable organic matter (SEOM) corresponding to 11.4% of the PM₁₀ concentration and 38.6 μg m^− 3 with 5.9 μg m^− 3 SEOM corresponding to 15.2% for PM_2.5. PM concentration and SEOM varied with the season and the particle size. The quantification of nitro-polycyclic aromatic hydrocarbons (nitro-PAH) was developed through the standards addition method under two schemes: reference standard with and without matrix, the former giving the best results. The recovery percentages varied with the extraction method within the 52 to 97% range depending on each nitro-PAH. The determination of the latter was effected with and without sample purification, also termed fractioning, giving similar results. 8 nitro-PAH were quantified, and their sum ranged from 111 to 819 pg m^− 3 for PM₁₀ and from 58 to 383 pg m^− 3 for PM_2.5, depending on the season. The greatest concentration was for 9-Nitroanthracene in PM₁₀ and PM_2.5, detected during the cold-dry season, with a median (10th-90th percentiles) concentration in 235 pg m^− 3 (66-449 pg m^− 3) for PM₁₀ and 73 pg m^− 3 (18-117 pg m^− 3) for PM_2.5. The correlation among mass concentrations of the nitro-PAH and criteria pollutants was statistically significant for some nitro-PAH with PM₁₀, SEOM in PM₁₀, SEOM in PM_2.5, NO_X, NO₂ and CO, suggesting either sources, primary or secondary origin. The measured concentrations of nitro-PAH were higher than those reported in other countries, but lower than those from Chinese cities. Knowledge of nitro-PAH atmospheric concentrations can aid during the surveillance of diseases (cardiovascular and cancer risk) associated with these exposures.     

Size distribution of airborne particles controls outcome of epidemiological studies

Epidemiological studies typically using wide size range mass metrics (e.g. PM₁₀) have demonstrated associations between airborne particulate matter and several adverse health outcomes. This approach ignores the fact that mass concentration may not correlate with regional lung dose, unlike the case of trace gases. When using measured particle size distributions as the basis for calculating regional lung dose, PM₁₀ mass concentration is found to be a good predictor of the mass dose in all regions of the lung, but is far less predictive of the surface area and particle number dose. On the other hand, measurements of particle number do not well predict mass dose, indicating that the chosen particle metric is likely to determine the health outcomes detectable by an epidemiological study. Consequently, epidemiological studies using mass metrics (PM_2.5 and PM₁₀) may fail to recognise important health consequences of particulate matter exposure, leading to an underestimate of the public health consequences of particle exposure.     

Particulate matter emitted from ultrasonic humidifiers—Chemical composition and implication to indoor air

Household humidification is widely practiced to combat dry indoor air. While the benefits of household humidification are widely perceived, its implications to the indoor air have not been critically appraised. In particular, ultrasonic humidifiers are known to generate fine particulate matter (PM). In this study, we first conducted laboratory experiments to investigate the size, quantity, and chemical composition of PM generated by an ultrasonic humidifier. The mass of PM generated showed a correlation with the total alkalinity of charge water, suggesting that CaCO₃ is likely making a major contribution to PM. Ion chromatography analysis revealed a large amount of SO₄²⁻ in PM, representing a previously unrecognized indoor source. Preliminary results of organic compounds being present in humidifier PM are also presented. A whole-house experiment was further conducted at an actual residential house, with five low-cost sensors (AirBeam) monitoring PM in real time. Operation of a single ultrasonic humidifier resulted in PM_2.5 concentrations up to hundreds of μg m⁻³, and its influence extended across the entire household. The transport and loss of PM_2.5 depended on the rate of air circulation and ventilation. This study emphasizes the need to further investigate the impact of humidifier operation, both on human health and on the indoor atmospheric chemistry, for example, partitioning of acidic and basic compounds.     

Effects of agriculture crop residue burning on children and young on PFTs in North West India

Variations in pulmonary function tests (PFTs) due to agriculture crop residue burning (ACRB) on children between the age group of 10 to 13 years and the young between 20 to 35 years are studied. The effects of exposure to smoke due to rice-wheat crop residue burning on pulmonary functions like Force Vital Capacity (FVC), Force Expiratory Volume in one second (FEV₁), Peak Expiratory Flow (PEF) and Force Expiratory Flow in 25 to 75% of FVC (FEF_25-75%) on 40 healthy subjects of rural/agricultural area of Sidhuwal village of Patiala City were investigated for a period from August 2008 to July 2009. Measurements were taken by spirometry according to the American Thoracic Society standards. High volume sampler (HVS) and Anderson Impactor were used to measure the concentration levels of SPM, PM₁₀ and PM_2.5 in ambient air of the Sidhuwal village. A significant increase in the concentration levels of SPM, PM₁₀ and PM_2.5 was observed due to which PFTs of the subjects showed a significant decrease in their values, more prominently in the case of children. PFTs of young subjects recovered up to some extent after the completion of burning period but the PFT values of children remained significantly lower (p < 0.001) even after the completion of burning episodes. Small size particulate matter (PM_2.5 and PM₁₀) affected the PFTs to a large extent in comparison to the large size particulate matter (SPM). The study indicates that ACRB is a serious environmental health hazard and children are more sensitive to air pollution, as ACRB poses some unrecoverable influence on their PFTs.     

Size-dependent particulate matter indoor/outdoor relationships for a wind-induced naturally ventilated airspace

We applied a simple size-dependent indoor air quality model associated with measured outdoors particulate matter (PM) profiles and potential loss mechanisms to characterize PM indoor/outdoor (I/O) relationships for wind-induced naturally ventilated residences in Taiwan region. The natural ventilation rate was quantified by the opening effectiveness for sidewall opening and covered ridge with sidewall-opening-type homes. The measured results demonstrate that integrated PM₁₀ and PM_2.5 mass concentrations for the urban area are 39.2 and $\text{3.13}\text{μg}\text{m}{}^{\mathrm{-3}}$, respectively, whereas for the suburban area are 75.76 and $\text{69.87}\text{μg}\text{m}{}^{\mathrm{-3}}$, respectively. The most significant removal mechanisms included natural ventilation through and particle deposition on indoor surfaces. The predicted average PM mass I/O ratios were 0.56 and 0.42 for PM_2.5 and PM₁₀, respectively. We also employed published data on mass-weighted size distributions for specific chemical constitutes of PM, sulfate and nitrate, to predict PM I/O ratios in the central Taiwan region; the resulting values ranged from 0.22 to 0.43 and 0.27 to 0.36 for sulfate and nitrate, respectively. Our results demonstrate that the PM I/O ratios for a wind-induced natural ventilated airspace depend strongly on the ambient particle distributions, building openings design (e.g. height-to-length ratio of openings and roof slope), wind speed, wind angle of incidence, and outdoor PM metrics.     

Infiltration of fine particles in urban daycares

Singapore is a tropical country with a high density of day-care facilities whose indoor environments may be adversely affected by outdoor fine particle (PM_2.5) air pollution. To reduce this problem requires effective, evidence-based exposure-reduction strategies. Little information is available on the penetration of outdoor PM_2.5 into day-care environments. Our study attempted to address the following objectives: to measure indoor infiltration factor (F_inf) of PM_2.5 from outdoor PM_2.5 and to determine the building parameters that modify the indoor PM_2.5. We collected indoor/outdoor 1-min PM_2.5 from 50 day-care classrooms. We noted mean F_inf ± SD of 0.65 ± 0.22 in day-care rooms which are naturally ventilated and lower F_inf ± SD values of 0.47 ± 0.18 for those that are air-conditioned: values which are lower than those reported in Singapore residences. The air exchange rates were higher in naturally ventilated rooms (1.47 vs 0.86 h⁻¹). However, fine particle deposition rates were lower for naturally ventilated rooms (0.67 ± 0.43 h⁻¹) compared with air-conditioned ones (1.03 ± 0.55 h⁻¹) presumably due to composite rates linked to the filters within the split unit air-conditioners, higher recirculation rates, and interior surfaces in the latter. Our findings indicate that children remaining indoor in daycares where air-conditioning is used can reduce their PM_2.5 exposures during outdoor pollution episodes.     

Metal concentration of PM2.5 and PM10 particles and seasonal variations in urban and rural environment of Agra, India

Three monthly 24-hour samples of airborne aerosols (PM₁₀ and PM_2.5) were collected at an urban and a rural site of the North central, semi-arid part of India during May 2006 to March 2008. Seven trace metals (Pb, Zn, Ni, Fe, Mn, Cr and Cu) were determined for both sizes. The annual mean concentration for PM₁₀ was 154.2 µg/m³ and 148.4 µg/m³ at urban and rural sites whereas PM_2.5 mean concentration was 104.9 µg/m³ and 91.1 µg/m³ at urban and rural sites, respectively. Concentrations of PM₁₀ and PM_2.5 have been compared with prescribed WHO standards and NAAQS given by CPCB India and were found to be higher. Weekday/weekend variations of PM₁₀ and PM_2.5 have been studied at both monitoring sites. Lower particulate pollutant levels were found during weekends, which suggested that anthropogenic activities are major contributor of higher ambient particulate concentration during weekdays. Significant seasonal variations of particulate pollutants were obtained using the daily average concentration of PM₁₀ and PM_2.5 during the study period. PM_2.5/PM₁₀ ratios at urban and rural sites were also determined during the study period, which also showed variation between the seasons. Three factors have been identified using Principal Component Analysis at the sampling sites comprising resuspension of road dust due to vehicular activities, solid waste incineration, and industrial emission at urban site whereas resuspension of soil dust due to vehicular emission, construction activities and wind blown dust carrying industrial emission, were common sources at rural site.     

Fine and ultrafine particle removal efficiency of new residential HVAC filters

Particle air filters used in central residential forced‐air systems are most commonly evaluated for their size‐resolved removal efficiency for particles 0.3‐10 µm using laboratory tests. Little information exists on the removal efficiency of commercially available residential filters for particles smaller than 0.3 µm or for integral measures of mass‐based aerosol concentrations (eg, PM_2.5) or total number concentrations (eg, ultrafine particles, or UFPs) that are commonly used in regulatory monitoring and building measurements. Here, we measure the size‐resolved removal efficiency of 50 new commercially available residential HVAC filters installed in a recirculating central air‐handling unit in an unoccupied apartment unit using alternating upstream/downstream measurements with incense and NaCl as particle sources. Size‐resolved removal efficiencies are then used to estimate integral measures of PM_2.5 and total UFP removal efficiency for the filters assuming they are challenged by 201 residential indoor particle size distributions (PSDs) gathered from the literature. Total UFP and PM_2.5 removal efficiencies generally increased with manufacturer‐reported filter ratings and with filter thickness, albeit with numerous exceptions. PM_2.5 removal efficiencies were more influenced by the assumption for indoor PSD than total UFP removal efficiencies. Filters with the same ratings but from different manufacturers often had different removal efficiencies for PM_2.5 and total UFPs.     

Cooking‐related PM2.5 and acrolein measured in grocery stores and comparison with other retail types

We measured particulate matter (PM), acrolein, and other indoor air contaminants in eight visits to grocery stores in California. Retail stores of other types (hardware, furniture, and apparel) were also sampled on additional visits. Based on tracer gas decay data, most stores had adequate ventilation according to minimum ventilation rate standards. Grocery stores had significantly higher concentrations of acrolein, fine and ultrafine PM, compared to other retail stores, likely attributable to cooking. Indoor concentrations of PM_2.5 and acrolein exceeded health guidelines in all tested grocery stores. Acrolein emission rates to indoors in grocery stores had a mean estimate about 30 times higher than in other retail store types. About 80% of the indoor PM_2.5 measured in grocery stores was emitted indoors, compared to only 20% for the other retail store types. Calculations suggest a substantial increase in outdoor air ventilation rate by a factor of three from current level is needed to reduce indoor acrolein concentrations. Alternatively, acrolein emission to indoors needs to be reduced 70% by better capturing of cooking exhaust. To maintain indoor PM_2.5 below the California annual ambient standard of 12 μg/m³, grocery stores need to use air filters with an efficiency rating higher than the MERV 8 air filters commonly used today.     

Fine particulate air pollution and daily mortality in Shenyang, China

Fine particulate matter (PM_2.5) is not a criteria pollutant in China, and few studies were conducted in the country to investigate the health impact of PM_2.5. In this study, we did a time-stratified case-crossover analysis to examine the association between PM_2.5 and daily mortality in Shenyang, an industrial center in northeast China. Daily mortality, air pollution and weather data from August 1, 2006 to December 31, 2008 in Shenyang were collected. A time-stratified case-crossover approach was used to estimate the association of PM_2.5 with both total and cause-specific mortality. Controls were selected as matched days of the week in the same month. Potential effect modifiers, such as age, gender, and season, were also examined. We found significant associations between PM_2.5 and daily mortality in Shenyang. A 10 μg/m³ increment in the 2-day moving average (lag 01) concentrations of PM_2.5 corresponded to 0.49% (95% CI: 0.19%, 0.79%), 0.53% (95% CI: 0.09%, 0.97%), and 0.97% (95% CI: 0.01%, 1.94%) increase of total, cardiovascular, and respiratory mortality, respectively. The associations appeared to be stronger in older people (aged ≥ 75 years), in females and during the warm season. To our knowledge, this is the longest PM_2.5 health study in time duration in China. Our findings provide new information on the adverse health effects of PM_2.5, and may have implications for environmental policy making and standard setting in China.