Outdoor Particles Research Articles

Potencijalni uticaj zabrane kretanja tokom COVID-19 pandemije na parametre životne sredine

COVID-19 had an impact on the daily life, human activities, various sectors, and the environment. Accordingly, the aim of this research was to examine the effect of the COVID-19 pandemic lockdown (COVID-19 PL) on the environmental parameters. The studied environmental parameters were solid waste, noise, air, water, wastewater (WW), soil and green areas, natural environment and resources, light pollution, radiation pollution, energy and others. The main environmental issues were divided into seventy sub-parameters. Results revealed that COVID-19 PL increased a number of parameters, such as domestic and hospital wastes, noise at home, aquatic life and water quality, domestic WW amount, green areas, animal and birds movement, natural energy, rodents etc.; while, it decreased several factors for instance commercial/industrial solid waste, traffic and outdoor noises, air pollution and particles, water contamination, WW production, cutting trees and hunting, fuel extraction and mining, artificial light and radiation, fuel combustion, tourist etc. Alternatively, some parameters, such as black water, natural radiation, and normal lighting remained as before COVID-19 PL. Positive, nil, and negative impacts of the parameters on the environment due to COVID-19 PL were 81.43 %, 5.71 %, and 12.86 %, respectively. Positive impacts of the COVID-19 PL on the environment were greater than negative influences and lockdown was regarded as a respiration of the natural environment. Currently, prediction of seasonal impact on spreading COVID-19 is difficult.

Indoor and Outdoor Particulate Matter Exposure of Rural Interior Alaska Residents

To assess the exposure of residents in rural communities in the Yukon Flats to particulate matter of 2.5 μm or less in diameter (PM2.5), both indoor and outdoor concentration observations were carried out from March to September 2019 in Ft. Yukon, Alaska. Indoor concentrations were measured at 0.61 m (breathing level during sleeping) in homes and at 1.52 m heights (breathing level of standing adult) in homes and office/commercial buildings. Air quality was better at both heights in cabins than frame homes both during times with and without surface-based inversions. In frame houses, concentrations were higher at 0.61 m than 1.52 m, while the opposite is true typically for cabins. Differences between shoulder season and summer indoor concentrations in residences were related to changes in heating, subsistence lifestyle and mosquito repellents. In summer, office and commercial buildings, air quality decreased due to increased indoor emissions related to increased use of equipment and mosquito pics as well as more merchandise. During summer indoor concentrations reached unhealthy for sensitive groups to hazardous conditions for extended times that even exceeded the high outdoor concentrations. Due to nearby wildfires, July mean outdoor concentrations were 55.3 μg·m-3 which exceeds the 24-h US National Ambient Air Quality Standard of 35 μg·m-3. Indoor and outdoor concentrations correlated the strongest with each other for office/commercial buildings, followed by frame houses and cabins. Office/commercial buildings with temperature monitors had one to two orders of magnitude lower concentrations than those without.

Cooking and electronic cigarettes leading to large differences between indoor and outdoor particle composition and concentration measured by aerosol mass spectrometry.

We spend about two thirds of our time in private homes where airborne particles of indoor and outdoor origins are present. The negative health effects of exposure to outdoor particles are known. The characteristics of indoor airborne particles, though, are not well understood. This study assesses the differences in chemical composition of PM1 (<1 μm) inside and outside of an occupied Swedish residence in real time with a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) and an Aethalometer. The chemical composition and concentration of particles indoors showed large differences compared to outdoors. The average indoor concentration was 15 μg m-3 and was higher than the outdoor 7 μg m-3. Organics dominated indoor particle composition (86% of the total mass) and originated from indoor sources (cooking, e-cigarette vaping). The average indoor to outdoor ratios were 5.5 for organic matter, 1.0 for black carbon, 0.6 for sulphate, 0.1 for nitrate, 0.2 for ammonium and 0.2 for chloride. The occupancy time accounted for 97% of the total measured period. Four factors were identified in the source apportionment of organic particle fraction by applying positive matrix factorization (PMF): two cooking factors, one e-cigarette factor and one outdoor contribution (OOA) organic factor penetrated from outside.

Assessment of exposure by size-resolved indoor and outdoor particle sources in residential buildings

Assessment of exposure by size-resolved indoor and outdoor particle sources in residential buildings

Nanoparticle Behaviour in an Urban Street Canyon at Different Heights and Implications on Indoor Respiratory Doses

The amount of outdoor particles that indoor environments receive depends on the particle infiltration factors (Fin), peculiar of each environment, and on the outdoor aerosol concentrations and size distributions. The respiratory doses received, while residing indoor, will change accordingly. This study aims to ascertain to what extent such doses are affected by the vertical distance from the traffic sources. Particle number size distributions have been simultaneously measured at street level and at about 20 m height in a street canyon in downtown Rome. The same Fin have been adopted to estimate indoor aerosol concentrations, due to the infiltration of outdoor particles and then the relevant daily respiratory doses. Aerosol concentrations at ground floor were more than double than at 20 m height and richer in ultrafine particles. Thus, although aerosol infiltration efficiency was on average higher at 20 m height than at ground floor, particles more abundantly infiltrated at ground level. On a daily basis, this involved a 2.5-fold higher dose at ground level than at 20 m height. At both levels, such doses were greater than those estimated over the period of activity of some indoor aerosol sources; therefore, they represent an important contribution to the total daily dose.

Characteristics of indoor and outdoor fine particles in heating period at urban, suburban, and rural sites in Harbin, China.

Concurrent indoor-outdoor fine particulate matter (PM2.5) measurements were conducted at urban, suburban, and rural sites in Harbin, a megacity in the northeast of China. Chemical constituents of indoor-outdoor PM2.5 were determined. Infiltration factors (FINF) of all sites were calculated according to the indoor to outdoor (I/O) ratios of PM2.5 based on the regression analysis. Linear discriminant analysis (LDA) is applied to determine the indoor-outdoor relationship. Secondary organic carbon (SOC) was calculated on the basis of organic carbon to elemental carbon (OC/EC) ratios. The mean concentrations of indoor and outdoor PM2.5 were 166.4 ± 32.5 μg/m3 and 228.4 ± 83.7 μg/m3, respectively, during the heating period. OC/EC and potassium ion to elemental carbon (K+/EC) ratios verified that biomass was an important source in Harbin especially for rural sites. The nitrate to sulfate (NO3-/SO42-) ratio indicates the higher contribution of traffic emissions in urban sites. Cr was the only species that exceeded the guidelines of WHO 2002, which was mainly emitted from coal and oil combustion. SOC/OC and NO3-/SO42- ratios, and ion-balanced acidity (the ratio of cation to anion, R+/-) showed a large urban-rural and indoor-outdoor difference. The highest SOC/OC ratio was found at urban sites, up to 38.3% for indoors. SOC/OC ratios and R+/- values of indoor environments were higher, which is attributed to the conducive condition of forming the secondary pollutants during the heating period. The results of LDA indicated that the distributions of the chemical components of PM2.5 at three sites were statistically dissimilar. Graphical abstract.

Simulation and evaluation of sheltering efficiency of houses equipped with ventilation systems

When an air pollution or extreme weather event occurs, outdoor particles entering a house may affect the indoor air quality and endanger human health. We began researching the sheltering efficiency of houses by determining the penetration factor. This involved using a test chamber to simulate the process of outdoor particles passing through cracks of a household sliding window and elucidating the most effective sheltering configuration of houses in air pollution emergencies. The results illustrate that a high air exchange rate corresponds to a high penetration factor, and the concentration difference between outdoor and indoor affects ventilation efficiency. For universal household sliding windows, frames made of plastic coupled with an air exchange rate less than or equal to 1.20 h−1 can prevent particle penetration more effectively in air pollution emergencies. As the external particles gradually disperse and the concentration decreases, a ventilation system with a large air exchange rate may effectively purify the indoor air. However, UFPs of less than 69 nm are able to undergo penetrate in a large amount, especially when the air exchange rate is lower than 1.20 h−1. Therefore, effective housing sheltering is still a challenge if the external source is primarily UFPs. In addition, laboratory simulations may overestimate/underestimate the penetration factor and the ventilation efficiency if the particles with a one charging state are the only source.

Long-term exposure to black carbon in outdoor air pollution is associated with cancer incidence

PDS 76: Source specific outdoor air pollution studies, Exhibition Hall (PDS), Ground floor, August 26, 2019, 4:30 PM - 5:30 PM Background/Aim: There is growing evidence that outdoor fine particles (PM2.5) cause cancer, but the individual effects of their many components remain to be understood. We investigated the relationships between black carbon (a by-product of combustion mainly from anthropogenic sources) and cancer incidence in Gazel, a large French population-based cohort. Methods: Gazel included 19,349 participants followed up until 2015, among which we identified 4,042 cases of incident all-site cancer and 342 for lung cancer. We estimated exposure to black carbon and PM2.5 using a land-use regression developed for 2010, which we extrapolated yearly to each participant address between 1990 and 2015. Our main exposure metric was the log-transformed cumulative exposure to black carbon with a 10-year lag; we did the same for PM2.5 for subsequent adjustment. We used extended Cox models with attained age as underlying time-scale and time-dependent exposures. The main model included black carbon and adjusted for relevant confounders (including sex, tobacco, alcohol consumption, socio-economic status, calendar time). As secondary model, since black carbon is a component of PM2.5, we used the black carbon:PM2.5 ratio plus an interaction with PM2.5. Results: We found positive associations with all-site and lung cancer incidence, with respective hazard ratios of 1.17 (95% confidence interval 1.06-1.29) and 1.41 (1.03-1.94) per increase in log-transformed cumulative black carbon exposure. When adjusted for PM2.5, we found hazard ratios of 1.51 (1.12-2.02) and 2.22 (0.74-6.71) for a 10% increase in the black carbon:PM2.5 ratio for all-site and lung cancer incidence, respectively. Conclusions: These findings highlight black carbon as a potential candidate to better understand the effects of air pollution on cancer incidence.

Infiltration of diesel exhaust from a loading dock into a nearby building

A loading dock is a common functional component of modern commercial and institutional buildings where substantial amount of air pollutants might be emitted by diesel trucks. This study aims to determine whether pollutants in a loading dock could infiltrate into nearby indoor environments through mechanic ventilation systems. We measured the levels of fine particulate matter (PM2.5) and black carbon (BC), and particle size distributions at a loading dock and inside three offices of a nearby building. We observed increased levels of PM2.5 and BC both at the loading dock and in the offices due to trucking activities. The infiltration factors (Fin), defined as the equilibrium fraction of outdoor particles that penetrates indoors, were greater for BC (range: 0.20–0.24) as compared with PM2.5 (range: 0.02–0.13) and were greater for larger particles in the size range of 7.64–289 nm. To reduce human exposures to those particles, an anti-idling policy was implemented at the loading dock as part of the study. As a result, the levels of PM2.5 and BC were significantly (p < 0.001) decreased at the loading dock, but the BC levels were increased in the offices due to elevated infiltration factors after the intervention. Our findings suggest that the location of building air intake, truck activities at the loading dock, and particle's infiltration rate are important factors affecting the indoor air quality of the nearby building.

Infiltration of fine particles in urban buildings

Singapore is a tropical country that can be affected by outdoor fine particle air pollution. Little information is available on the penetration of outdoor fine particles into daycare environments. Our study attempted to address the following objectives: to measure indoor infiltration factor (Finf of PM2.5 from outdoor fine particles and to determine the building parameters that modifies the indoor PM2.5. We collected indoor/outdoor 1-min PM2.5. from 50 daycare environments. We noted high indoor and outdoor concentrations of fine particles due to the presence of regional haze pollution. Indoor and outdoor fine particle concentrations are significantly highest for daycares located near highways while indoor to outdoor ratios were significantly lower for air-conditioning use in daycares. Mean Finf±SD of 0.65±0.19 in daycare rooms which are naturally ventilated and lower Finf±SD values of 0.46±0.22 for those that are air-conditioned. The penetration coefficients and air exchange rates were higher in naturally ventilated daycares (0.78 vs 0.61 and 1.47 vs 0.86 h−1 respectively). Our findings show that children remaining indoor in daycares where air conditioning is used can reduce PM2.5 exposures during outdoor pollution episodes.

Characteristics of school children's personal exposure to ultrafine particles in Heshan, Pearl River Delta, China – A pilot study

BackgroundThere is a significant lack of scientific knowledge on population exposure to ultrafine particles (UFP) in China to date. This paper quantifies and characterises school children's personal UFP exposure and exposure intensity against their indoor and outdoor activities during a school day (home, school and commuting) in the city of Heshan within the Pearl River Delta (PRD) region, southern China. MethodsTime-series of UFP number concentrations and average size were measured over 24 h for 24 children (9–13 years old), using personal monitors over two weeks in April 2016. Time-activity diaries and a questionnaire on the general home environment and potential sources of particles at home were also collected for each participating child. The analysis included concurrently measured size distributions of ambient UFP at a nearby fixed reference site (Heshan Supersite). ResultsHourly average UFP concentrations exhibited three peaks in the morning, midday and evening. Time spent indoors at home was found to have the highest average exposure (1.26 × 104 cm−3 during sleeping) and exposure intensity (2.41). While there is always infiltration of outdoor particles indoors (from nearby traffic and general urban background sources), indoor exposure at home was significantly higher than outdoor exposure. Based on the collected questionnaire data, this was considered to be driven predominantly by adults smoking and the use of mosquito repellent incense during the night. Outdoor activities at school were associated with the lowest average exposure (6.87 × 102 cm−3) and exposure intensity (0.52). ConclusionDespite the small sample size, this study characterised, for the first time, children's personal UFP exposure in a city downwind of major pollution sources of the PRD region in China. Particularly, the results highlighted the impact of smoking at home on children's exposure. While the study could not apportion the specific contributions of second hand-smoking and mosquito coil burning, considering the prevalence of smokers among the parents who smoke at home, smoking is a very significant factor. Exposure to second-hand smoke is avoidable, and these findings point out to the crucial role of government authorities and public health educators in engaging with the community on the role of air quality on health, and the severity of the impact of second-hand smoke on children's health.

A comparative study on arsenic fractions in indoor/outdoor particulate matters: a case in Baoding, China.

The distribution and bioavailability of arsenic (As) in indoor/outdoor total suspended particulates (TSP), inhalable particulate matters (PM10), and fine particulate matters (PM2.5) in Baoding, China were investigated. The average I/O ratios for TSP, PM10, and PM2.5 were 0.52, 0.66, and 0.96, respectively. There was no significant correlation between indoor/outdoor TSP, PM10, and PM2.5. The indoor/outdoor concentrations of As surpassed the limited value of As. I/O ratios of arsenic in TSP, PM10, and PM2.5 were 0.52, 0.58, and 0.55, respectively. The contents of arsenic in different fractions were mainly affected by the total concentrations of arsenic in particulate matters (PM) rather than the particle sizes for TSP and PM10. Arsenic was mainly in non-specifically sorbed fraction (F1) in both indoor and outdoor PM2.5. The evaluated carcinogenic risk (CR) was within the safe level. The bioavailability of As increased with particle size decreasing for both indoor and outdoor PM. The potential bioavailability of As in outdoor particles was higher than that of indoor particles with the same size, especially PM2.5.

Oxidative potential of particles at a research house: Influencing factors and comparison with outdoor particles

The oxidative potential (OP) of particles can be represented by the ability of particles to generate hydroxyl radicals in an aqueous solution which can be measured with electron paramagnetic resonance (EPR) spectrometry. The oxidative potential of particles may be a more health-relevant metric than other physicochemical properties of particles. While OPEPR has been measured in several outdoor locations, it remains largely unstudied in indoor environments. Total suspended particle samples were collected at an unoccupied research house in eighteen four-day sampling events. The OPEPR of indoor particles was found to be 59% ± 30% of the OPEPR of outdoor particles on a sampling volume basis during normal indoor conditions in eight sampling events. However, OPEPR per particle mass was 3.5 ± 0.62 times higher indoors than outdoors, indicating that reactions taking place indoors likely increase OPEPR of indoor particles. In ten sampling events, indoor temperature, relative humidity (RH), air change rate (λ), and cooking activities were varied. OPEPR of indoor particles was found to be significantly influenced (in order of importance) by indoor RH, λ, and temperature. OPEPR of indoor particles was higher than OPEPR for outdoor particles when indoor RH and λ were increased. The presence of cooking activities did not appear to consistently increase OPEPR of indoor particles.

Numerical analysis of PM2.5 particle collection efficiency of an electrostatic precipitator integrated with double skin façade in a residential home

In this study, the electrostatic precipitator (ESP) integrated with a double skin façade (DSF) was proposed as a new method to overcome natural ventilation constraints due to outdoor particles and the particle collection efficiency of an ESP integrated with a DSF (EPID) was evaluated using numerical analysis. The particle collection efficiencies of two models of ESP integrated with DSF (EPID) with air cavity depths of 0.2 m and 0.5 m were evaluated according to the horizontal and vertical installation positions of the ESP in the air cavity and the voltage intensity during operation. Changes in the particle collection efficiency depending on the inlet air velocity at the EPID inlet were also analyzed. A computational fluid dynamics model was suggested for analyzing the airflow in the EPID, particle behavior, and electrostatic precipitation and validated by comparison with existing experimental data. The particle collection efficiency of the EPID was high when it was adjacent to the inner skin of the EPID and located in the upper section of the air cavity, and positions inside the air cavity with a reduced velocity for the main airflow helped increase the particle collection efficiency. When the air velocity at the EPID inlet was controlled at 0.5 m/s, a particle collection efficiency of 92.8% could be expected at 12 kV. These results indicate that integrating the ESP with the DSF can effectively reduce the inflow of external particles.

Site- and house-specific and meteorological factors influencing exchange of particles between outdoor and indoor domestic environments

The aim of this study was to investigate the influence of site- and house-specific as well as meteorological factors on indoor and outdoor particle concentrations. Particle number (PN) and particle mass (PM) concentrations were monitored in 62 houses in Brescia, Northern Italy, during two winter monitoring periods. Measurements were conducted in houses of non-smokers and without the activation of any internal aerosol sources from domestic activities such as cooking and cleaning. Indoor and outdoor particle concentrations were measured for 30 min in each house. A wide-range aerosol spectrometer (MINIWRAS 1371, GRIMM) was used to detect 41 classes of particles from 10 nm to 35 μm. The effects of natural ventilation on indoor particle concentrations were also considered by measuring PM and PN indoor/outdoor ratios before and after a window was opened for a period of 15 min. An ANOVA analysis was performed on a sub-dataset of 35 houses to evaluate the dependence of PN and PM concentrations on site- and house-specific as well as meteorological factors. The house energy class was significantly related to indoor particle concentrations, and window dimensions seemed to influence the concentrations both before and after the ventilation period. We found that some factors, e.g., the floor level, need further investigation.

Sequential determination and chemical speciation analysis of inorganic As and Sb in airborne particulate matter collected in outdoor and indoor environments using slurry sampling and detection by HG AAS.

In this work, fast sequential determination and chemical speciation analysis of inorganic arsenic and antimony in airborne particulate matter collected in outdoor and indoor environments using slurry sampling and detection by hydride generation atomic absorption spectrometry (HG-AAS) is proposed. A Doehlert design was applied to optimise the hydride generation conditions of As and Sb for fast sequential determination in the same aliquot of particulate matter samples after preparation of the slurry. The limits of quantification (LoQ) obtained for As and Sb were 0.3 and 0.9 ng m-3, respectively. The accuracy of the analytical method was confirmed by analysis of the certified reference material of urban particulate matter (SRM NIST 1648a), presenting concordance with certified values of 92.7±7.7% for As and 91.2±9.5% for Sb. Precision was expressed as relative standard deviation (% RSD, n=3), with our results presenting values better than 3.4% and 4.2% for total inorganic As and Sb, respectively. For all analysed samples, total As concentrations and its inorganic species were below the LoQ of the analytical method (<0.3 ng m-3). However, the averages of total inorganic Sb concentrations in airborne particulate matter, collected as total suspended outdoor particles (TSPoutdoor), inhalable particulate matter (PM10), and total suspended indoor particles (TSPindoor), were 3.1±0.5, 2.4±0.6, and 2.6±0.4 ng m-3, respectively. Trivalent Sb (Sb3+) was the predominant inorganic species in all samples investigated, with mean percentages of 76%, 72%, and 73% in TSPoutdoor, PM10, and TSPindoor, respectively. The presence of Sb and its predominant inorganic form (Sb3+) can be attributed to vehicular traffic close to the sampled urban areas. Therefore, fast sequential determination of As and Sb and their inorganic species in particulate matter samples prepared as slurry by FS-HG-AAS is an efficient, accurate, and precise method and can be successfully applied to routine analysis.

Infiltration of outdoor combustion-generated pollutants to indoors due to various ventilation regimes: A case of a single-family energy efficient building

The paper presents the quantitative assessment of the influence of various ventilation regimes on particulate matter and polycyclic aromatic hydrocarbon concentrations in the newly built, low energy unoccupied house. Experimental measurements were conducted over five-week period of February–March, which is affected by combustion particles resulting from residential heating and traffic in outdoor air. Number concentrations of particles (PNC0.3-10), mass concentration of PM2.5, as well as vapor and particle phase polycyclic aromatic hydrocarbons (PAHs) were measured both outdoors and indoors during several ventilation regimes. Ventilation regime with minimum natural and no mechanical ventilation (air change rate (ACR) of 0.16 1/h) caused the lowest infiltration of outdoor pollutants in this particular building as represented by I/O ratio of PM2.5 (0.22), PNC0.3-10 (0.20), and total PAHs (0.23 and 0.33 for particle and vapor phase, respectively). Natural ventilation via leaky windows regime (ACR – 0.42 1/h) caused the highest infiltration of the particles and PPAHs (I/O PM2.5–0.45, PNC0.3-10 – 0.51, and PPAHs - 0.47). At the same time, mechanical ventilation resulted in the highest I/O of VPAHs of 0.58 at ACR of 0.80 1/h, while I/O of PPAHs were moderate (0.38–0.45). Such results indicate that outdoor combustion particles are only partially arrested in a filter commonly installed in air handling units (grade F7, ePM2.5 = 66%). At the same time, conventional residential air filtration systems are less efficient in the removal of gas phase pollutants, which needs to be addressed by specific engineering measures.

Seasonal variations of indoor air quality and thermal conditions and their correlations in 220 classrooms in the Midwestern United States

In this 2-year, seasonally-repeated study, the research team surveyed the baseline conditions of indoor air quality (IAQ) and thermal conditions (TC) of 220 classrooms in the Midwestern region (Nebraska and Iowa) of the United States of America. Seasonal variations of each IAQ and TC variable and correlations between variables were also examined. CO2 concentrations were acquired from each of the classrooms while simultaneously monitoring outdoor CO2 concentration, particle counts, formaldehyde concentration, air temperature, globe temperature, and relative humidity. Ventilation rate and absolute humidity level were also estimated. The results showed the mean CO2 concentration of 220 classrooms during the occupied hours throughout the measured seasons was 1171 ppm. The average ventilation rate was 5.6 L/s-person, below the suggested value by ASHRAE Std 62.1. Other IAQ and TC variables were found to be well-maintained when compared to the NIOSH or EPA standards. Large seasonal variations were found in humidity level, ventilation rate, particle counts, and formaldehyde concentration. It is therefore suggested that the monitoring of classroom IAQ and TC should be done periodically across the whole school year to comprehensively describe the conditions. There were significant correlations between IAQ and TC variables, which suggest relationships between these variables. This study revealed the baseline conditions and examined the seasonal variations of the classroom IAQ and TC of the region for the first time. Further benefits, such as improvement of classroom IAQ and TC, may result from this study.

Comparison of different window behavior modeling approaches during transition season in Beijing, China

Window operation is an important occupant behavior, and has significant impacts on building energy consumption. Recently, various stochastic and non-stochastic models have been proposed, aiming to describe occupant window behavior based on several influencing factors. However, most of the employed methods are logit regression and Markov chain techniques, and the application of machine learning to model occupants' window behavior is rarely investigated. In addition, most published studies referring to occupants' window behavior have been carried out within European countries, where the influence of outdoor air quality is rarely considered. This study compares different models of occupants’ window behavior, including models based on logistic regression, Markov processes, and an artificial neural network. An artificial neural network model is proposed to explore the application and optimization of an artificial neural network algorithm under a condition of having less samples. Moreover, the outdoor fine inhalable particles (PM2.5) concentration is considered as an influencing factor for building a window opening model for office buildings during the transition season in China. From this work, it is generally concluded that the PM2.5 concentration and outdoor humidity should be considered in the modeling of occupant window behavior in Beijing, China. In addition, more true estimations can be obtained from artificial neural network models than from logistic regression models and Markov models. This result demonstrates that the proposed artificial neural network yields a prediction model of office window states with higher accuracy and better interpretability of highly correlated factors as compared to logistic regression models and Markov models. The proposed approaches provide a new and detailed way for engineers and building operators to better understand occupant window behaviors and their impacts on energy use in office buildings.

Commuter exposure to particulate matters in four common transportation modes in Nanjing

Particulate matter (PM) is one of the major air pollutants in China. Traffic-related microenvironments are the typical scenarios exposed to high PM concentrations. This paper investigates the personal exposure to PM during commuting in Nanjing in four transportation modes, i.e. subway, bicycle, bus and walking. The measurements were conducted in a heavy-traffic street during rush hours in summer and winter. The result reveals significant PM concentration differences between various commuting modes. Passengers in subway cabin are exposed to lowest PM1 (38.3 μg/m3) and PM2.5 (54.4 μg/m3) concentrations, while passengers in subway station are exposed to highest PM2.5 (90.5 μg/m3). Pedestrians are exposed to highest PM1 (59.5 μg/m3). Both outdoor and indoor-generated particles contribute a lot to the particles in subway station and 63.4% of the PM2.5 generated in subway station are between 1 μm and 2.5 μm in size. Most particles in subway cabin are from subway station and most particles in bus cabin come from the outdoor air, while indoor sources contribute little. Spatial particle concentration variations were observed in subway station. The particle concentration at a deeper level is usually higher than the concentration at a shallower level. Substantial particles within 1–2.5 μm in size were observed at the platform and the portion within 1–2.5 μm decreased at shallower levels. The PM inhalation during subway trip is lowest while the inhalations during walking and cycling are more than 5 times higher. During a short distance subway trip, the exposure in subway station contributes most of the total particle inhalation during the entire subway trip.