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The unfavorable locations of underground infrastructures and poor ventilation facilities can result in the deterioration of enclosed air quality. Some researchers have studied air quality and ventilation measures in different types of underground buildings. However, few studies have investigated the pollution in pedestrian passageways connecting underground structures. Hence, in this paper, we attempted to investigate the spatial distribution of fine particulate matter (PM 2.5 ) in underground passageways. First, measurements were designed and conducted in a pedestrian passageway beneath the Shanghai South Railway Station, Shanghai, China. Second, numerical simulations were performed based on computational fluid dynamic (CFD) technology. Finally, the numerical simulations were extended to examine impacts of the ventilation measures on PM 2.5 concentration with different inlet positions and air velocity in underground passageways. The simulation results showed good agreement with the experimental data, and the numerical model was validated to be an effective method to investigate the spatial distribution of PM 2.5 in underground passageways. Results suggest that building additional entrances is an advisable method for improving air quality in the underground passageways of the Shanghai South Railway Station, while jet fans are not recommended. Findings of this study offer suggestions for mitigating PM 2.5 pollution in underground passageways.

• Spatial distribution prediction of pollutants based on machine learning. • A new approach to planning urban ventilation corridors. • Cleanliness assessment of the air at the compensation spaces should be made mandatory. • Urban ventilation corridors worsen air quality in the central city. Urban ventilation corridors are effective in improving urban air quality and alleviating heat island problems, and are widely used in cities around the world. This paper studies typical smog-polluted cities in China to examine whether urban ventilation corridors will worsen air pollution in cities and then proposes countermeasures. First, this paper identifies compensation spaces outside the central urban area of Xi'an and then analyses the prevailing wind direction in these compensation spaces. Based on these findings, this paper identifies potential cold air passages and assesses the air cleanliness in these compensation spaces according to the spatial distributions of PM 2.5 and PM 10. The study finds that four compensation spaces are found outside the central urban area of Xi'an and seven potential cold air passages, including six expressways and one railway, and the PM 10 and PM 2.5 concentrations in three of the four compensation spaces are higher than those in the central urban area. From the beginning (located in the compensation space) to the end (located in the action space) of the cold air passages P1 and P2, PM 2.5 decreased by 11.88% and 11.82%, and PM 10 decreased by 9.40% and 9.76%. This study discovers that if the urban compensation spaces are located in areas with high concentrations of pollutants, the polluted cold air will be introduced to the central urban area along the cold air passages due to the prevailing wind. Unlike previous studies which concluded that urban ventilation corridors improve air quality in central urban areas, this study demonstrates that urban ventilation corridors are at risk of exacerbating air pollution in central urban areas. Therefore, when planning urban ventilation corridors, a city should make an assessment of the air cleanliness of the compensation spaces mandatory to avoid worsening air pollution in the central urban area and creating an unsustainable climate environment due to the planning of urban ventilation corridors, which may further lead to economic losses and threats to public health. [ABSTRACT FROM AUTHOR]

Abstract Air pollution is widely believed to cause healthy risks and influence nations' economic dimensions. This paper investigates the impact of air pollution on housing prices in China's 286 prefectural-level cities during 2005–2013. To address the endogeneity problem of PM 2.5 concentrations in our regression, we propose an instrument variable strategy based on ventilation coefficient. The estimation results suggest that a 10% increase in PM 2.5 concentrations causes a 2.4% reduction in local housing prices. Air pollution also hinders the progress of urbanization, limits cities' human capital formation and changes people's expectations of housing prices that we interpret as three potential mechanisms behind our main findings. [ABSTRACT FROM AUTHOR]

Abstract: By means of computational fluid dynamic (CFD) simulations, this paper investigated how rural winds transport relatively clean air into high-rise urban areas to dilute airborne pollutants. Two ventilation concepts for indoor environments were applied: the age of air to quantify the time taken by rural young air to reach a given place after it enters an urban area and the air exchange efficiency to evaluate the efficiency of rural winds flushing the entire urban canopy layer. Several square building arrays with street aspect ratios (building height/street width, H/W) ranging from 1.5 to 5.3 and building area densities of 0.25 (medium) or 0.4 (compact) were considered as the approaching wind is parallel to the main street whose length varies from street scales to neighborhood scales (330–510 m to 1.03–1.65 km in full-scale). Results show that considerable young rural air enters windward entries but a major fraction of air is vertically driven out as flowing deeper into such high-rise building arrays. So air exchange efficiencies are less than 50% in street-scale arrays, and smaller in longer (neighborhood-scale) or narrower arrays. For the neighborhood-scale medium arrays, considering the power-law velocity profile in the upstream free flow, a taller array gains a larger inflow rate across its windward entry and experiences younger air and greater air exchange efficiency than a lower one. If all buildings are theoretically open-based in a neighborhood-scale compact array, air becomes much younger everywhere and the air exchange efficiency doubles. In arrays of buildings with different heights, the secondary streets in front of taller buildings get younger air due to the downward flows within them. Although further investigations are still required before providing a practical framework, this paper is one of the first attempts to find ways in improving the ventilation performance in high-rise cities like Hong Kong. [Copyright &y& Elsevier]

Pneumonia is a major cause of childhood morbidity in China. Many studies of rural areas have found an association between pneumonia and air pollution from burning of bio-mass. The present study is of children living in urban, modern homes without burning of bio-mass. In order to investigate potential home risk factors associated with children’s pneumonia, China Child Home Health (CCHH) questionnaires were randomly distributed to parents of 6461 children in 23 kindergartens in all 11 districts of Nanjing, covering urban, suburban, and industrial areas. The 4014 valid questionnaires (response rate 65.7%) were returned and have been analyzed. The lifetime incidence of pneumonia in Nanjing children 1–8 years old is 26.7%. The incidence of croup, asthma and frequent common colds was strongly associated with pneumonia, as was a history of allergies in the family, and persons other than parents (for example grandparents or nanny) taking care of the child. Several home environmental factors, namely, dampness, lack of ventilation, using coal or natural gas (electricity as reference) for cooking, new furniture, and “modern” floor and wall covering materials were also significantly associated with pneumonia. The indoor environment typical of modern apartments in China was a risk factor for pneumonia among children. [ABSTRACT FROM AUTHOR]

This article analyses ideas about indoor air pollution, fresh and foul air, ventilation and modern hygiene in China during the century between 1849 and 1949. The main focus is on conceptions of and provisions against air pollution in China during this period. The article scrutinises the early history of air pollution in China through a study of the introduction of scientific information, the foreign inspiration for health, hygiene and ventilation, the popular discourse, and the dissemination of knowledge about air quality, fresh air and ventilation. Air pollution in this article is understood in a broad sense involving all airborne substances seen to have adverse health effects on humans, thus including ideas about the positive and negative health effects of clean and fresh air, dust particles, germs and sunshine. This is a story of how science and technology formed part of the history of transmission of knowledge from West to East and how this knowledge took on new and indigenous forms in its Chinese context. This analysis can serve as a historical grounding for understanding current interpretations of fresh and foul air in China today. [ABSTRACT FROM AUTHOR]

The Chinese national pollution census has indicated that the domestic burning of solid fuels is an important contributor to nitrogen dioxide ( NO2) and sulfur dioxide ( SO2) emissions in China. To characterize indoor NO2 and SO2 air concentrations in relation to solid fuel use and stove ventilation in the rural counties of Xuanwei and Fuyuan, in Yunnan Province, China, which have among the highest lung cancer rates in the nation, a total of 163 participants in 30 selected villages were enrolled. Indoor 24-h NO2 and SO2 samples were collected in each household over two consecutive days. Compared to smoky coal, smokeless coal use was associated with higher NO2 concentrations [geometric mean ( GM) = 132 μg/m3 for smokeless coal and 111 μg/m3 for smoky coal, P = 0.065] and SO2 [limit of detection = 24 μg/m3; percentage detected (%Detect) = 86% for smokeless coal and 40% for smoky coal, P < 0.001]. Among smoky coal users, significant variation of NO2 and SO2 air concentrations was observed across different stove designs and smoky coal sources in both counties. Model construction indicated that the measurements of both pollutants were influenced by stove design. This exposure assessment study has identified high levels of NO2 and SO2 as a result of burning solid fuels for cooking and heating. [ABSTRACT FROM AUTHOR]

In China, with the rapid economic development and improvement of living standards over the past few decades, the household living environment has shifted dramatically. The aim of the present study is to assess the impact of home environment factors on respiratory symptoms and asthma in Chinese children. Investigators analyzed data collected in the 25 districts from the seven Northeastern cities to examine health effects on respiratory symptoms and asthma in 31,049 children aged 2-14 years. Factor analysis was used to reduce 33 children's lifestyle and household variables to six new 'factor' variables. The multiple indicators multiple causes approach was used to examine the relationship between indoor air pollution and respiratory health status, controlling for covariates. Factor analyses generated six factor variables of potential household risk factors from an original list of 33 variables. The respiratory symptoms and asthma were significantly associated with the recent home renovation factor (estimate = 0.076, p < 0.001), pet ownership factor (estimate = 0.095, p < 0.001), environmental tobacco smoke (ETS) exposure factor (estimate = 0.181, p < 0.001) and PVC-flooring factor (estimate = 0.031, p = 0.007). Home ventilation factor was not related to any respiratory condition (estimate = 0.028, p = 0.074). Independent respiratory health effects existed for multiple household environmental factors recent home renovation, pet ownership, ETS, and PVC-flooring. [ABSTRACT FROM AUTHOR]

Poor Indoor Air Quality (IAQ) in air-conditioned offices can have adverse effects on occupants like discomfort and productivity loss. Strategic IAQ monitoring and assessment conducted with optimized resources for representative pollutants and air sampling have therefore been developed. This study evaluates the performance of a proposed simple screen process on an IAQ express assessment protocol (EAP) to identify in the office environment asymptomatic unsatisfactory IAQ. This screening process was conducted with an 'IAQ index', correlated with an event of unsatisfactory IAQ through the 'failure' due to other unmeasured air pollutant levels in the EAP. In this case the IAQ index is defined as the average fractional dose within certain exposure limits from the assessed top dominant contributors identified from a regional database of IAQ assessment results for workplaces. The accuracy of the proposed assessment protocol was tested with a regional IAQ database developed from IAQ measurements of common air pollutants in 422 air-conditioned offices of Hong Kong and compared with the EAP. It is reported that the application of the screening process in the EAP would improve the overall performance of the IAQ assessment without additional measurement parameters. The proposed screening protocol of the EAP would be a useful source of reference in setting up any IAQ assessment policies. [ABSTRACT FROM AUTHOR]

Long-term measurement results of indoor air quality (IAQ) over a general community can be used to evaluate the effectiveness of mitigation measures for IAQ improvement of premises. However, this approach requires considerable measurement efforts and thus the complete data sets are not available in many circumstances. This study proposes an epistemic approach in estimating the probable influences of an IAQ policy for Hong Kong offices, using the regional IAQ measurement databases of offices in 1996, 1998-2001 and 2004-2005. After the implementation of the IAQ policy in 1997-1999, measurement results of IAQ in offices were collected and were used to quantify the IAQ improvement for Hong Kong offices. It is noted that IAQ dissatisfaction due to air pollutants predominated by indoor emissions of volatile organic compounds (VOCs) might need additional attentions for an effective IAQ improvement programme. Practical application: This study provides updated information on the forecasts of IAQ in air-conditioned offices of Hong Kong due to the influence of the IAQ policy implemented in 1997-1999. It is a useful source of reference for policymakers and decision makers in evaluating an indoor air pollution control policy for air-conditioned offices. [ABSTRACT FROM AUTHOR]