Smog Events Research Articles

Fault tree analysis of the causes of urban smog events associated with vehicle exhaust emissions: A case study in Jinan, China

The excessive consumption of fuels associated with rapid industrialization, urbanization, and modernization has caused serious smog events in many Chinese cities. Vehicle exhaust is one of the primary causes of smog events due to the rapid growth of motor vehicle ownership and increased fuel consumption. In this study, fault tree analysis (FTA) was used as a relatively simple but effective way to analyze the causes of smog associated with vehicle exhaust emissions in Jinan, China. First, after the identification of the top event, intermediate events, and basic events, a comprehensive fault tree system for urban smog associated with vehicle exhaust emissions was constructed. Then, during the qualitative analysis stage, minimal cut sets (MCSs) were grouped using Boolean algebra operations, and the original fault tree was simplified to an equivalent tree based on 6 MCSs. Finally, during the quantitative analysis stage, the effects of the 12 basic events on the top event were evaluated and ranked according to the structural importance, probabilistic importance, and critical importance of their analytical measures. Our results indicated that traffic congestion, superabundance of vehicles, poor supervision, and yellow-label vehicles with long use ages had the greatest impact on smog events, with importance degrees of 0.52930, 0.52920, 0.22719, and 0.22716, respectively. These results are consistent with common sense. Although different basic events exert different influences, all of the basic events should be comprehensively taken into consideration and corresponding precautionary measures developed. This research provides a good case study of the application of FTA in the analysis of the causes of urban smog events associated with vehicle exhaust emissions. Our study further demonstrates that FTA is a relatively simple but effective method for the causal analysis of smog, as well as an effective tool for environmental risk management.

洛杉矶雾霾事件的城市规划应对之启示

洛杉矶雾霾事件的城市规划应对之启示

Extensible Database of Validated Biomass Smoke Events for Health Research

The extensible Biomass Smoke Validated Events Database is an ongoing, community driven, collection of air pollution events which are known to be caused by vegetation fires such as bushfires (also known as wildfire and wildland fires), or prescribed fuel reduction burns, and wood heaters. This is useful for researchers of health impacts who need to distinguish smoke from vegetation versus other sources. The overarching aim is to study statistical associations between biomass smoke pollution and health. Extreme pollution events may also be caused by dust storms or fossil fuel smog events and so validation is necessary to ensure the events being studied are from biomass. This database can be extended by contribution from other researchers outside the original team. There are several available protocols for adding validated smoke events to the database, to ensure standardization across datasets. Air pollution data can be included, and free software was created for identification of extreme values. Protocols are described for reference material needed as supporting evidence for event days. The utility of this database has previously been demonstrated in analyses of hospitalization and mortality. The database was created using open source software that works across operating systems. The prospect for future extensions to the database is enhanced by the description in this paper, and the availability of these data on the open access Github repository enables easy addition to the database with new data by the research community.

In this issue of Weather

We begin the last issue of 2018 with an account of severe surface icing, due to freezing rain, in the Czech Republic in 2014. This phenomenon is difficult to forecast, given the critical balance between surface (and ground) temperatures and the warm advection that is bringing rain, rather than snow. The paper by P. Zahradníček and his co‐authors ‘The December 2014 glaze event in the Czech Republic: predictability and impacts’ portrays this well, beginning on p. 375.Our 24th annual review of climate from the Hadley Centre at the Met Office begins on p. 382. ‘Global and regional climate in 2017’ by John Kennedy and his co‐authors shows how warm and wet much of the globe remained last year, despite the absence of El Niño conditions.On p. 394, Ian Strangeways’ paper ‘William Henry Dines – a blue plaque commemoration’ gives us an account of the celebration of the addition, earlier this year, of a sign marking the life and work of a pioneer in meteorology in Benson (Oxfordshire).Smog events – now largely absent in Europe and North America – are becoming an increasing hazard in the development world as cities grow and more people need to travel. The effects of a smog event in a northeastern Indian city are given by Sunil Gupta and Suresh Elumalai in ‘Adverse impacts of fog events during winter on fine particulate matter, CO and VOCs: a case study of a highway near Dhanbad, India’ on p. 396.On p. 402, our last paper moves on to consider the details and effects of one of last year's damaging North Atlantic hurricanes as it affected Puerto Rico: ‘Hurricane Maria: 12 hours that changed the history of a country’ by Rafael Mendez Tejeda.

An important mechanism of regional O<sub>3</sub> transport for summer smog over the Yangtze River Delta in eastern China

Abstract. Severe ozone (O3) pollution episodes plague a few regions in eastern China at certain times of the year, e.g., the Yangtze River Delta (YRD). However, the formation mechanisms, including meteorological factors, contributing to these severe pollution events remain elusive. A severe summer smog stretched over the YRD region from 22 to 25 August 2016. This event displayed hourly surface O3 concentrations that exceeded 300 µg m−3 on 25 August in Nanjing, an urban area in the western YRD. The weather pattern during this period was characterized by near-surface prevailing easterly winds and continuous high air temperatures. The formation mechanism responsible for this O3 pollution episode over the YRD region, particularly the extreme values over the western YRD, was investigated using observation data and by running simulations with the Weather Research and Forecasting model with Chemistry (WRF-Chem). The results showed that the extremely high surface O3 concentration in the western YRD area on 25 August was largely due to regional O3 transport in the nocturnal residual layer (RL) and the diurnal change in the atmospheric boundary layer. On 24 August, high O3 levels, with peak values of 220 µg m−3, occurred in the daytime mixing layer over the eastern YRD region. During nighttime from 24 to 25 August, a shallow stable boundary layer formed near the surface which decoupled the RL above it from the surface. Ozone in the decoupled RL remained quite constant, which resulted in an O3-rich “reservoir” forming in this layer. This reservoir persisted due to the absence of O3 consumption from nitrogen oxide (NO) titration or dry deposition during nighttime. The prevailing easterly winds in the lower troposphere governed the regional transport of this O3-rich air mass in the nocturnal RL from the eastern to the western YRD. As the regional O3 transport reached the RL over the western YRD, O3 concentrations in the RL accumulated and rose to 200 µg m−3 over the western Nanjing site during the sunrise hours on 25 August. The development of the daytime convective boundary layer after sunrise resulted in the disappearance of the RL, as the vertical mixing in the convective boundary layer uniformly redistributed O3 from the upper levels via the entrainment of O3-rich RL air down to the O3-poor air at the ground. This net downward transport flux reached up to 35 µg m−3 h−1, and contributed a considerable surface O3 accumulation, resulting in severe daytime O3 pollution during the summer smog event on 25 August in the western YRD region. The mechanism of regional O3 transport through the nocturnal RL revealed in this study has great implications regarding understanding O3 pollution and air quality change.

Smog analysis and its effect on reported ocular surface diseases: A case study of 2016 smog event of Lahore

A comparative cross sectional study was conducted in order to analyze the pollutants (CO, NOx, SO2, O3, VOC and PM) present in the event of Lahore smog that was observed on 2–5 Nov 2016 in relation to the baseline condition of the ambient air measured during the same period in the previous year i.e. 2015. The effect of smog was determined based on ocular surface diseases reported by patients, using data taken from tertiary care hospitals during the 2–3 November 2016 Lahore smog. The data was compared with that from the previous year (2–3 November 2015) being considered as baseline. For analysis of the smog and its comparison with baseline conditions, three sites were selected within Lahore city i.e. Mall Road, Gulberg and Township. The AQI for these sites were determined with the analysis of ambient air that was done through USEPA approved reference methods. The data on the number of patients having ocular surface diseases due to smog were collected from tertiary care hospitals i.e. Shiekh Zaid and Mayo Hospitals which were randomly selected. The clinical method used has been implicitly elaborated and it has been explained very clearly how all the clinical diagnoses were executed. The highest concentration of pollutant analyzed during smog was that of NOx which was almost 17 times higher than the baseline value. The other pollutants SO2 and O3 were four times, CO, VOC and PM2.5 two times and PM10 was six times higher than the baseline value. Although the values of SO2 and PM2.5 were greater than the baseline values they did not exceed the Pakistan Environmental Quality Standards (PEQS) limits. The Air Quality Index- AQI was found to be six times higher than the baseline which represents a very poor air quality during smog days. The metrological conditions during the smog event were cool temperatures, calm winds and high humidity that ultimately triggered the photochemical reaction which caused the smog. The data taken from hospitals revealed that out of 700 patients 200 were reported in 2015 and 500 were reported in 2016 with diseases including dry eyes (12%) and (13%), irritation (20%) and (21%), lid erosion (4%) and (5%), corneal diseases (7%) and (8%),uveitis (3%) and (4%) and lacrimation (11%) and (7%) respectively. The study ultimately revealed that there was a 60% increase in the number of patients reported with ocular surface diseases (dry eyes, irritation, lid erosion, corneal diseases, conjunctival diseases, uveitis, and lacrimation) during periods of smog as compared to baseline conditions.

Air pollution and control: Past, present and future

The quality of air is closely related to everyone’s life. However, due to the intense industrialization and urbanization, air pollution has affected or is affecting the health of the public. Since the notorious London smog and the Los Angeles photochemical smog events, the air pollution has been developing rapidly in recent years in some developing countries such as China and India. The essence of air pollution hazard is the impact of air pollutants on human health and environment. In view of the fragmentation of the research and one-sided knowledge of someone on air pollution and control, this paper is documented to review the whole status of technology development in this research field, to clarify the formation and elimination mechanism of air pollution, to correctly understand the hazard of air pollution and to promote the precise management of air pollution control. The research of the air pollution hazard is essentially the study of the effect of atmospheric pollution on human health and environment. The past, present and future status of air pollution and its control will be reviewed in this paper from the perspective of physical, chemical and biological process which are be modeling using mathematical technique, coding and programing. Meanwhile, the history, present and existing problems on atmospheric physics, atmospheric chemistry, emission inventory, atmospheric environment monitoring, meteorological field forecast, air quality forecast, source apportionment and tracing source, the impact of air pollution on human health, and atmospheric pollution control are well summarized. From the classical analytical methods developed in the middle of the last century such as the Gaussian method to the numerical methods generally used so far, the physical processes of transmission, diffusion and sedimentation of pollutant are described and solved. The chemical processes represented by the London smog incident mainly sulfur compounds, by Los Angeles photochemical smog mainly O3 and nitrogenous compounds, and by Beijing-Tianjin-Hebei fog-haze pollution mainly mixture of nitrogen- containing compounds and sulfur-based compounds have made breakthrough progresses, and the chemical mechanism are basically clear. A series of biological effects will be occurred when the pollutants are inhaled. The chemical composition of air pollutants will have oxidative stress reactions, lipid peroxidation and DNA damage, causing inflammation, cardiovascular disease, cancer and birth defects. At present, the research on the physical process is relatively mature, and the accuracy and effective days of weather forecast are increasing and extending gradually. However, the two-way feedback mechanism of meteorology and atmospheric pollution is still a difficult issue. The understanding of the main chemical processes is basically clear, but a large number of unknown reaction mechanisms need to be further explored, especially the chemical mechanism of the explosive growth of PM2.5. Cognition of biological processes is still preliminary, which are based primarily on statistical analysis but lack a theoretical basis and are needed to be further explored. The theoretical framework, as well as core issues of air pollution hazard identification and control, are be put forward and pointed out based on the theories, techniques, methods and standards of inversion and generation of emission sources, particle toxicity identification, chemical process assimilation, health risk prediction and early warning, synchronization source apportionment of predicting results, and dynamic optimal control are not yet mature, which are the main focus for future development, due to the extremely complicated and staggered influence as well as constraints on physical process, chemical process, biological process as well as mathematical description and computer calculation principle of air pollution and prevention. If the toxicity of pollutants is directly related to health risks, which may provide more direct, effective and scientific technological support for air pollution emergency optimal control as well as the optimal issues of industrial, energy structure adjustment and heavy pollution sources layout, it will play a fundamental role to meet the objective needs of identifying accurately pollution sources, achieving targeted management and promoting ecological civilization construction.

Seasonal Source Apportionment of PM2.5 in Ningbo, a Coastal City in Southeast China

With the rapid economic development and urbanization of China, haze and photochemical smog events have been frequently observed during the last decade. To explore the temporal and spatial pollution characteristics in Ningbo, a medium-sized coastal city located in the Yangtze River Delta (YRD) in southeast China, 24-h PM2.5 (particulate matter with aerodynamic diameter ≤ 2.5 µm) samples were simultaneously collected at five sites (two urban residential sites, two urban coastal sites, and one suburban site) from winter 2012 to autumn 2013. The average PM2.5 concentration was 53.2 ± 30.4 µg m–3. Furthermore, the concentration exhibited a seasonal variation: It was highest in winter and lowest in summer. The urban residential sites had the highest PM2.5 concentrations, followed by the urban coastal sites, and the suburban site had the lowest concentration. OM (Organic Matters) and secondary inorganic ions (sulfate, nitrate, and ammonium) were the dominant components of the PM2.5. As a coastal city with industrial zones, sources are more complex in Ningbo than in inland cities due to ship emissions and the interactions between land and sea, and the marine and atmospheric environments. Positive matrix factorization (PMF) was used to apportion the particle sources. Nine factors were resolved in this study: secondary nitrate, vehicle exhaust, secondary sulfate, coal combustion, industrial emission, ship emission, dust, biomass burning, and aged sea salt, with average contributions of 26%, 21%, 13%, 12%, 9%, 7%, 5%, 4%, and 3%, respectively. Secondary nitrate and vehicle exhaust were the major sources of PM2.5 pollution in Ningbo. Coal combustion contributed significantly in winter and autumn, whereas sea salt formed a considerable contribution in summer. This study suggests that decreasing the PM2.5 pollution in Ningbo requires not only strategies for reducing local primary sources but also joint inter-regional prevention and the control of air pollution in the YRD.

Metagenomic profiling of ARGs in airborne particulate matters during a severe smog event

Information is currently limited regarding the distribution of antibiotic resistance genes (ARGs) in smog and their correlations with airborne bacteria. This study characterized the diversity and abundance of ARGs in the particulate matters (PMs) of severe smog based on publicly available metagenomic data, and revealed the occurrence of 205 airborne ARG subtypes, including 31 dominant ones encoding resistance to 11 antibiotic types. Among the detectable ARGs, tetracycline, β-lactam and aminoglycoside resistance genes had the highest abundance, and smog and soil had similar composition characteristics of ARGs. During the smog event, the total abundance of airborne ARGs ranged from 4.90 to 38.07ppm in PM2.5 samples, and from 7.61 to 38.49ppm in PM10 samples, which were 1.6–7.7 times and 2.1–5.1 times of those in the non-smog day, respectively. The airborne ARGs showed complicated co-occurrence patterns, which were heavily influenced by the interaction of bacterial community, and physicochemical and meteorological factors. Lactobacillus and sulfonamide resistance gene sul1 were determined as keystones in the co-occurrence network of microbial taxa and airborne ARGs. The results may help to understand the distribution patterns of ARGs in smog for the potential health risk evaluation.

Public attention to the great smog event: a case study of the 2013 smog event in Harbin, China

The 2013 outbreak of smog in China triggered unprecedented public attention in the country, which played a critical role in crisis communication and management. This study explores the determinants that influence public attention from the non-smog-stricken cities to the smog events. Following the literature on proximity, this study identified three influencing factors, namely cognitive, geographical, and organizational proximity, between two cities. We tested these factors by analyzing the public attention to the smog event that occurred in Harbin, China, on October 21, 2013. Data collected from Sina Weibo yielded 5409 Harbin smog-related Weibo posts sent between October 20, 2013, and October 31, 2013, from 113 cities. Results provide some support for the hypothesis.

Heterogeneous Reactions between Toluene and NO2 on Mineral Particles under Simulated Atmospheric Conditions.

Heterogeneous reactions between organic and inorganic gases with aerosols are important for the study of smog occurrence and development. In this study, heterogeneous reactions between toluene and NO2 with three atmospheric mineral particles in the presence or absence of UV light were investigated. The three mineral particles were SiO2, α-Fe2O3, and BS (butlerite and szmolnokite). In a dark environment, benzaldehyde was produced on α-Fe2O3. For BS, nitrotoluene and benzaldehyde were obtained. No aromatic products were produced in the absence of NO2 in the system. In the presence of UV irradiation, benzaldehyde was detected on the SiO2 surface. Identical products were produced in the presence and absence of UV light over α-Fe2O3 and BS. UV light promoted nitrite to nitrate on mineral particles surface. On the basisi of the X-ray photoelectron spectroscopy (XPS) results, a portion of BS was reduced from Fe3+ to Fe2+ with the adsorption of toluene or the reaction with toluene and NO2. Sulfate may play a key role in the generation of nitrotoluene on BS particles. From this research, the heterogeneous reactions between organic and inorganic gases with aerosols that occur during smog events will be better understood.

Overexpression of HO-1 assisted PM2.5-induced apoptosis failure and autophagy-related cell necrosis

Severe smog/haze events accompanied by extremely high concentrations of airborne fine particulate matter (PM2.5) have emerged frequently in China and the potential health risks have attracted ever-growing attention. During these episodes, a surge in hospital visits for acute respiratory symptoms and respiratory diseases exacerbation has been reported to be associated with acute exposure to high-levels of particulate matters. To investigate cell fate determination and the underlying pathogenic mechanisms during severe haze episodes or smog events, we exposed human lung epithelial cells (BEAS-2B) to PM2.5 (0–400μg/mL) for 24h and found that high doses of PM2.5 caused cell necrosis and autophagy dysfunction, while co-treatment with the autophagy inhibitor 3-MA could partially reduce PM2.5-induced cell necrosis. Exposure to PM2.5 also increased the expression and mitochondrial transposition of heme oxygenase 1 (HO-1), which consequently reduced the release of cytochrome C from mitochondria to cytosol. Knockdown of HO-1 by siRNA attenuated the mitochondrial accumulation of HO-1, reversed HO-1-induced the reduction of cytochrome C release and promoted PM2.5-induced cell apoptosis. In contrast to necrosis, PM2.5-induced autophagy was independent of HO-1. In conclusion, our results demonstrate that acute exposure to high PM2.5 concentrations causes autophagy-related cell necrosis. The decrease in cytochrome C release and apoptosis by upregulation of HO-1 maybe assist PM2.5-induced autophagy-related cell necrosis. Further, this study reveals dual roles for HO-1 in PM2.5-induced cytotoxicity and presents a possible explanation for the onset of acute respiratory symptoms under extreme particulate air pollution.

The health policy implications of individual adaptive behavior responses to smog pollution in urban China

Smog pollution is a serious public health issue in urban China, where it is associated with public health through a range of respiratory and cardiovascular illnesses. Despite the negative health impacts of smog pollution, individual adaptive behaviors are poorly understood. This knowledge gap hinders the development of effective public policy to support and encourage the adoption of individual adaptive and mitigating behaviors to smog pollution. A questionnaire survey of 1141 randomly sampled individuals in a typical PM2.5-polluted Chinese city was designed to establish smog concerns and behavior changes during smog events. The results demonstrate a variety of behavior responses associated with risk perception, experience of smog, age, and gender of respondents. An understanding of these variations is critical to the development of effective public policy and ultimately to the improvement of public health in cities affected by smog.

Adoption of Protective Behaviours: Residents Response to City Smog in Hefei, China

City smog outbreaks in many Chinese cities aroused public concern about health risks and environmental pollution in China. This study investigates protective behaviours of the citizens in response to city smog using protective action decision to understand their actions. A survey was conducted in Hefei, Anhui in 2015, after the city experienced severe smog events. The data from 429 respondents supported the developed model. Hazard‐related attributes were the strongest predictors for willingness to adopt protective behaviours. Public risk perception only positively affected self‐protective actions. Information sources affected risk perception and increased the respondents’ self‐protective intentions. Older adults and respondents with lower educational levels were more likely to adopt environmentally friendly actions. The findings’ theoretical and practical implications are also discussed.

Challenging the air quality discourse – people create pollution not technology

The London Smog of 1952 and subsequent health effects brought about a public outcry which triggered the generation and implementation of the UK’s Clean Air Act of 1956. This act and subsequent updates has been credited with ending the ‘pea-souper’ conditions synonymous with industrial and domestic coal burning. In recent years in the UK, the emergence of major smog events in urban areas due to road transport emissions, the growing volume of epidemiological evidence on the health effects of air pollution, the threat of fines by the European Commission towards Member states and the high profile court cases taken forward by ClientEarth against HM Government1has once again raise the media and political profile of air pollution but the same public outcry that was evident after the London Smog has not been seen. This story is replicated around the world, where major air pollution incidents are not (yet) resulting in wide scale social action – and consequent political changes – to our approach to tackling air pollution.

Who should be blamed? The attribution of responsibility for a city smog event in China

The frequently occurring city smog in China has become a hot topic and raised extensive discussion in the public health domain. Our study tries to explore how citizens attribute causation and responded to city smog in Hefei, Anhui Province. The data from 420 respondents generally answered our research questions. The result suggests that attribution of responsibility can be influenced by risk perception, citizens’ occupation and source reliance. Attribution of responsibility, source reliance and risk perception can affect the citizens’ protective actions.

Characterization of Background Aerosol Properties during a Wintertime Smog Episode

The aim of this paper is to study the wintertime physical properties of atmospheric aerosol particles on the basis of data observed at the K-puszta regional background station in Hungary. In Hungary wintertime smog episodes are linked to strong stable air (high pressure blocking events) with thermal inversion. These atmospheric conditions are frequently formed during winter months (November–February) due to the special geographical location of the country. The formation of smog events is highly probable in cases of thermal inversion periods sustaining for at least 4 days. We discuss in the paper the role of high-pressure blocking events in aerosol properties in terms of PM10 concentrations, aerosol size distributions, new particle formation and optical properties. We found that high-pressure blocking events have significant impacts on the size distribution and particle formation processes. At K-puszta the aerosol is in highly aged state with size distribution dominated by the accumulation mode. This is further supported by the optical properties, e.g., by high scattering Angstrom exponent and by relatively weak absorption. The most significant effect of extreme episodes is manifested in the changes in PM10 concentrations and, consequently, in aerosol optical properties. The PM10 concentrations, scattering coefficients and absorption coefficients considerably increase to extreme values that are characteristic of a heavily polluted atmosphere rather than rural air. Our results indicate that in winter, the air quality at Kpuszta is often influenced by regional air pollution as shown by spatial distribution of PM10 concentration. It is found that PM10 had almost the same concentration in regional background air and in different types of urban environments. The special meteorological conditions and the role of regional-scale transport can explain why local abatements in cities cannot lead to significant improvement of the air quality during smog events.

Satellite and Ground Observations of Severe Air Pollution Episodes in the Winter of 2013 in Beijing, China

ABSTRACTBeginning in early January 2013, Beijing experienced multiple prolonged and severe smog events that were characterized by very high levels of PM2.5, with peak daily PM2.5 over 400 µg m–3. With PM2.5 concentration contours created from ground observations and satellite remote sensing data, we describe the spatial and temporal characteristics of these episodes and further investigated the factors that contributed to these episodes. Our results indicated that these smog episodes affected a much larger geographic region, far beyond Beijing metropolitan area, corresponding to a total area of ~550,000 km2 and ~180 million people. The extremely cold weather in December 2012 and regional pollution transport were likely the main causes of these severe PM pollutions. In addition to aggressive emission control measures for Beijing, coordinated regional policy must be put in place to achieve more blue-sky days. Although the configuration of the current ground monitoring network may be sufficient to record PM2.5 levels in urban centers, these monitors alone cannot fully characterize the spatial pattern and track the transport of air pollution on a regional scale. Satellite remote sensing data can provide valuable information to fill the gaps left by ground monitors to create a more comprehensive picture of PM2.5.

The smog pollution in Handan - a mining and industrial city in China

Numerous smog events have occurred in recent years in China. Their hazards in mining and industrial cities are more serious than clear days. The samples were collected in the mining and industrial city of Handan. During the smog episode, PM10 and PM2.5 concentrations reach up to 980 μg/m3 and 660 μg/m3, respectively. Under SEM (scanning electron microscope) analysis, the particles consist of soot, fly ash and minerals, which could be from coal mines, power plants, steel mills and auto exhausts. Compared with the samples collected on a clear day, the increased PM10 particles are mainly composed of organic matter, especially aromatic compounds. The Pb content in PM10 of the smog day reaches 507.4 ng/m3 and could be caused by vehicle emissions.

Smog episodes, fine particulate pollution and mortality in China

BackgroundStarting from early January 2013, northern China was hit by multiple prolonged and severe smog events which were characterized by extremely high-level concentrations of ambient fine particulate matter (PM2.5) with hourly peaks of PM2.5 over 800µg/m3. However, the consequences of this severe air pollution are largely unknown. This study investigates the acute effect of the smog episodes and PM2.5 on mortality for both urban and rural areas in northern China. Data and methodsWe collected PM2.5, mortality, and meteorological data for 5 urban city districts and 2 rural counties in Beijing, Tianjin and Hebei Province of China from January 1, 2013 through December 31, 2013. We employed the generalized additive models to estimate the associations between smog episodes or PM2.5 and daily mortality for each district/county. ResultsWithout any meteorological control, the smog episodes are positively and statistically significantly associated with mortality in 5 out of 7 districts/counties. However, the findings are sensitive to the meteorological factors. After controlling for temperature, humidity, dew point and wind, the statistical significance disappears in all urban districts. In contrast, the smog episodes are consistently and statistically significantly associated with higher total mortality and mortality from cardiovascular/respiratory diseases in the two rural counties. In Ji County, a smog episode is associated with 6.94% (95% Confidence Interval, −0.20 to 14.58) increase in overall mortality, and in Ci County it is associated with a 19.26% (95% CI, 6.66–33.34) increase in overall mortality. The smog episodes kill people primarily through its impact on cardiovascular and respiratory diseases. On average, a smog episode is associated with 11.66% (95% CI, 3.12–20.90) increase in cardiovascular and respiratory mortality in Ji County, and it is associated with a 22.23% (95% CI, 8.11–38.20) increase in cardiovascular and respiratory mortality in Ci County. A 10μg/m3 increase in PM2.5 concentration is associated with 0.88% (95% CI, 0.3–1.46) increase in overall mortality and 1.2% (95% CI, 0.55–1.85) in Ji County. A 10μg/m3 increase in PM2.5 concentration is associated with 0.55% (95% CI, −0.02 to 1.13) increase in overall mortality in Ci County. The findings suggest that the smog episodes and fine particulate have bigger and more detrimental impacts on rural residents, especially for those living close to big and polluted cities. ConclusionsThe smog episodes and PM2.5 are statistically associated with mortality in rural areas of China. The associations for urban areas are not statistically significant.