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Background: Despite mounting evidence linked pneumonia with air pollution, it is unclear what main pollutant(s) exposure in which critical window(s) play a key role in pneumonia., Objective: To examine effects of intrauterine and post-natal exposure to air pollution on children's doctor-diagnosed pneumonia (DDP)., Methods: A combination of cross-sectional and retrospective cohort study was conducted at Changsha, China during 2019-2020. Personal exposure to outdoor air pollutants at each child's home address was estimated using inverse distance weighted (IDW) method based on data from 10 air quality monitoring stations. Associations between personal air pollution exposure and DDP were evaluated., Results: Children's DDP was associated with intrauterine and post-natal exposure to PM 2.5 , PM 2.5-10 , and PM 10 , adjusted ORs (95% CI) of 1.17 (1.04-1.30), 1.09 (1.01-1.17), and 1.07 (1.00-1.14) for IQR increase in intrauterine exposure and 1.12 (1.02-1.22), 1.13 (1.06-1.21), and 1.28 (1.16-1.41) for post-natal exposure. Intrauterine PM 2.5 exposure and post-natal PM 10 exposure were associated with a higher risk of pneumonia. We identified the 2nd trimester, 3rd trimester, and first year as critical windows respectively for PM 2.5 , PM 2.5-10 , and PM 10 exposure. Daytime exposure to traffic-related air pollution especially during early life increased DDP., Conclusion: Intrauterine and post-natal exposure to particulate matters played a dominant role in children's DDP., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Background: Pneumonia is a common disease worldwide in preschool children. Despite its large population size, China has had no comprehensive study of the national prevalence, risk factors, and management of pneumonia among preschool children. We therefore investigated the prevalence of pneumonia among preschool children in Chinese seven representative cities, and explore the possible risk factors of pneumonia on children, with a view to calling the world's attention to childhood pneumonia to reduce the prevalence of childhood pneumonia., Methods: Two group samples of 63,663 and 52,812 preschool children were recruited from 2011 and 2019 surveys, respectively. Which were derived from the cross-sectional China, Children, Homes, Health (CCHH) study using a multi-stage stratified sampling method. This survey was conducted in kindergartens in seven representative cities. Exclusion criteria were younger than 2 years old or older than 8 years old, non-permanent population, basic information such as gender, date of birth and breast feeding is incomplete. Pneumonia was determined on the basis of parents reported history of clearly diagnosed by the physician. All participants were assessed with a standard questionnaire. Risk factors for pneumonia, and association between pneumonia and other respiratory diseases were examined by multivariable-adjusted analyses done in all participants for whom data on the variables of interest were available. Disease management was evaluated by the parents' reported history of physician diagnosis, longitudinal comparison of risk factors in 2011 and 2019., Results: In 2011 and 2019, 31,277 (16,152 boys and 15,125 girls) and 32,016 (16,621 boys and 15,395 girls) preschool children aged at 2-8 of permanent population completed the questionnaire, respectively, and were thus included in the final analysis. The findings showed that the age-adjusted prevalence of pneumonia in children was 32.7% in 2011 and 26.4% in 2019. In 2011, girls (odds ratio [OR] 0.91, 95%CI [confidence interval]0.87-0.96; p = 0.0002), rural (0.85, 0.73-0.99; p = 0.0387), duration of breastfeeding ≥ 6 months(0.83, 0.79-0.88; p < 0.0001), birth weight (g) ≥ 4000 (0.88, 0.80-0.97; p = 0.0125), frequency of putting bedding to sunshine (Often) (0.82, 0.71-0.94; p = 0.0049), cooking fuel type (electricity) (0.87, 0.80-0.94; p = 0.0005), indoor use air-conditioning (0.85, 0.80-0.90; p < 0.0001) were associated with a reduced risk of childhood pneumonia. Age (4-6) (1.11, 1.03-1.20; p = 0.0052), parental smoking (one) (1.12, 1.07-1.18; p < 0.0001), used antibiotics (2.71, 2.52-2.90; p < 0.0001), history of parental allergy (one and two) (1.21, 1.12-1.32; p < 0.0001 and 1.33, 1.04-1.69; p = 0.0203), indoor dampness (1.24, 1.15-1.33; p < 0.0001), home interior decoration (1.11, 1.04-1.19; p = 0.0013), Wall painting materials (Paint) (1.16, 1.04-1.29; p = 0.0084), flooring materials (Laminate / Composite wood) (1.08, 1.02-1.16; p = 0.0126), indoor heating mode(Central heating)(1.18, 1.07-1.30, p = 0.0090), asthma (2.38, 2.17-2.61; p < 0.0001), allergic rhinitis (1.36, 1.25-1.47; p < 0.0001), wheezing (1.64, 1.55-1.74; p < 0.0001) were associated with an elevated risk of childhood pneumonia; pneumonia was associated with an elevated risk of childhood asthma (2.53, 2.31-2.78; p < 0.0001), allergic rhinitis (1.41, 1.29-1.53; p < 0.0001) and wheezing (1.64, 1.55-1.74; p < 0.0001). In 2019, girls (0.92, 0.87-0.97; p = 0.0019), duration of breastfeeding ≥ 6 months (0.92, 0.87-0.97; p = 0.0031), used antibiotics (0.22, 0.21-0.24; p < 0.0001), cooking fuel type (Other) (0.40, 0.23-0.63; p = 0.0003), indoor use air-conditioning (0.89, 0.83-0.95; p = 0.0009) were associated with a reduced risk of childhood pneumonia. Urbanisation (Suburb) (1.10, 1.02-1.18; p = 0.0093), premature birth (1.29, 1.08-1.55; p = 0.0051), birth weight (g) < 2500 (1.17, 1.02-1.35; p = 0.0284), parental smoking (1.30, 1.23-1.38; p < 0.0001), history of parental asthma (One) (1.23, 1.03-1.46; p = 0.0202), history of parental allergy (one and two) (1.20, 1.13-1.27; p < 0.0001 and 1.22, 1.08-1.37; p = 0.0014), cooking fuel type (Coal) (1.58, 1.02-2.52; p = 0.0356), indoor dampness (1.16, 1.08-1.24; p < 0.0001), asthma (1.88, 1.64-2.15; p < 0.0001), allergic rhinitis (1.57, 1.45-1.69; p < 0.0001), wheezing (2.43, 2.20-2.68; p < 0.0001) were associated with an elevated risk of childhood pneumonia; pneumonia was associated with an elevated risk of childhood asthma (1.96, 1.72-2.25; p < 0.0001), allergic rhinitis (1.60, 1.48-1.73; p < 0.0001) and wheezing (2.49, 2.25-2.75; p < 0.0001)., Conclusions: Pneumonia is prevalent among preschool children in China, and it affects other childhood respiratory diseases. Although the prevalence of pneumonia in Chinese children shows a decreasing trend in 2019 compared to 2011, a well-established management system is still needed to further reduce the prevalence of pneumonia and reduce the burden of disease in children., (© 2023. The Author(s).)

Mounting evidence have linked ambient air pollution and temperature with childhood pneumonia, but it is unclear whether there is an interaction between air pollution and temperature on childhood pneumonia. We aim to assess the combined effect of ambient air pollution and temperature exposure during preconception and pregnancy on pneumonia by a case-control study of 1510 children aged 0-14 years in Changsha, China. We obtained the data of childhood pneumonia from XiangYa Hospital electrical records. We estimated personal exposure to outdoor air pollution (PM 10 , SO 2 and NO 2 ) by inverse distance weighted (IDW) method and temperature indicators. Multiple logistic regression models were used to evaluate associations of childhood pneumonia with air pollution, temperature (T), and diurnal temperature variation (DTV). We found that exposure to industry-related air pollution (PM 10 and SO 2 ) during preconception and pregnancy were associated with childhood pneumonia, with ORs (95% CI) of 1.72 (1.48-1.98) and 2.96 (2.50-3.51) during 1 year before pregnancy and 1.83 (1.59-2.11) and 3.43 (2.83-4.17) in pregnancy. Childhood pneumonia was negatively associated with T exposure during 1 year before pregnancy and pregnancy, with ORs (95% CI) of 0.57 (0.41-0.80) and 0.85 (0.74-0.98). DTV exposure during pregnancy especially during the 1st and 2nd trimesters significantly increased pneumonia risk, with ORS (95% CI) of 1.77 (1.19-2.64), 1.47 (1.18-1.83), and 1.37 (1.07-1.76) respectively. We further observed interactions of PM 10 and SO 2 exposure with low T and high DTV during conception and pregnancy in relation to childhood pneumonia. This study suggests that there were interactions air pollution with temperature and DTV on pneumonia development., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Background: Increasing evidence have associated pneumonia with early exposure to ambient air pollution. However, the role of indoor environmental factors exposure in early life on childhood pneumonia remains unclear., Objective: To examine the association between indoor environmental factors exposure during different timing windows and childhood pneumonia, and to identify the key indoor factor(s) in different critical window(s)., Methods: A retrospective cohort study of 8689 pre-schoolers was performed in Changsha, China during 2019-2020. Our questionnaire survey was designed to collect information on pre-schooler's outcome and residential environmental exposure containing indoor pollution and allergens during 1 year before pregnancy, pregnancy, first year, and past year. The associations were further estimated stratified by personal exposure level of outdoor NO 2 , CO, temperature (T) and different covariates. Associations were assessed by multiple logistic regression model in terms of odds ratio (OR) of 95% confidence interval (CI)., Results: Pre-schooler's pneumonia was significantly related with exposure of new furniture, redecoration, mold/damp stains, and mold or damp clothing or bedding exposure during the four periods, with the strongest associations observed during 1 year before pregnancy based on multi-window model, with ORs (95% CI) of 1.27 (1.12-1.44), 1.26 (1.09-1.46), 1.34 (1.14-1.57), and 1.28 (1.05-1.56) respectively. Environmental tobacco smoke (ETS) including both parental and grandparental smoking were significantly related with increased risk of pre-schooler's pneumonia, and ETS played a more important role in early life, with ORs (95% CI) of 1.17 (1.01-1.36) and 1.19 (1.02-1.39) in pregnancy and first year. Indoor plants particularly nonflowering plants significantly elevated pneumonia risk but only in past year, with ORs (95% CI) of 1.17 (1.05-1.30) and 1.14 (1.03-1.26). Higher pneumonia risk was observed for renovation exposure in pre-birth compared to post-birth, while mold/dampness exerted an accumulative effect with the highest risk for exposure during both pre- and post-birth. Living near traffic road and exposure to high level of traffic-related air pollution and high temperature significantly increased pneumonia risk. Sensitivity analysis found that some sub-groups were more susceptible to pneumonia risk of home environment exposure., Conclusion: Early life exposure to indoor environmental factors plays an important role in pneumonia development, supporting the hypothesis of "Preconceptional and Fetal Origin of Childhood Pneumonia" and "Developmental Origins of Health and Pneumonia"., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Background: Pneumonia is the leading cause of death and hospitalization among young children worldwide, but its risk factors remain unclear., Objective: To evaluate the effect of maternal exposure to diurnal temperature variation (DTV) during preconceptional and prenatal periods on childhood pneumonia., Methods: A retrospective cohort study by case-control design was conducted for pneumonia (N = 699) and normal (N = 811) children under age of 14 who were enrolled in XiangYa Hospital, Changsha, China from May 2017 to April 2019. Demographic data including gender, age, birth season, gestational age, parity, mode of delivery, and parental atopy were collected from the electronic medical records in the hospital system. We obtained the data of daily DTV in Changsha during 2003-2019 from China Meteorological Administration. Maternal exposure to DTV during preconceptional and prenatal periods was respectively calculated by the average of daily DTV during one year and three months before conception and entire pregnancy as well as the three trimesters. The association between maternal exposure to outdoor DTV and childhood pneumonia was analyzed by multiple logic regression model., Results: We found that childhood pneumonia was significantly associated with exposure to an increase in DTV during one year before conception and entire pregnancy, with ORs (95 % CI) = 2.53 (1.56-4.10) and 1.85 (1.24-2.76). We further identified a significant risk of pneumonia of DTV exposure during the first and second trimester of pregnancy. Sensitivity analysis showed that boys were more susceptible to the effect of prenatal exposure to outdoor DTV during pregnancy particularly in the first two trimesters compared to girls., Conclusions: Preconceptional and prenatal exposure to DTV plays an important role in development of childhood pneumonia, especially during the first and second trimesters of pregnancy.

Background: Increasing evidence has linked childhood pneumonia with early exposure to ambient air pollution. However, the impact of exposure to air pollutants before birth is unclear., Objective: To further clarify whether exposure to a particular pollutant during preconceptional and prenatal periods, may pose a higher risk of developing childhood pneumonia., Methods: This case-control cohort study consisted of 1510 children aged 0-14 years in Changsha, China between 2017 and 2019. Data of children's history of pneumonia and blood biomarkers were obtained from the XiangYa Hospital records. Each child's exposure to air pollutants, including nitrogen dioxide (NO 2 ), sulfur dioxide (SO 2 ), and particulate matter with an aerodynamic diameter ≤ 10 µm (PM 10 ), was calculated using data from ten air pollution monitoring stations. A multivariate logistic regression model was used to quantify the relationship between childhood pneumonia and exposure to ambient air pollution during the preconceptional and prenatal periods., Results: Childhood pneumonia was significantly associated with preconceptional and prenatal exposure to the industrial-related air pollutant, SO 2 , for 1 year before conception, for 3 months before conception and for the entire pregnancy, with ORs(95% CI)= 4.01(3.17-5.07), 4.06(3.29-5.00) and 6.51(4.82-8.79). Also, children who were sick with pneumonia had higher white blood cell and neutrophil counts, and children with low eosinophil count or hemoglobin are likely to get pneumonia. Sensitivity analysis showed that boys, and children in high temperature area were susceptible to the effect of both preconceptional and prenatal exposure to industrial SO 2 ., Conclusion: Preconceptional and prenatal exposure to industrial-related air pollution plays a significant role in the incidence and progression of childhood pneumonia, supporting the hypothesis of "(pre-)fetal origin of childhood pneumonia"., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Biomass burning is associated with childhood pneumonia but few studies exist on other indoor factors., Aim: To study pneumonia in relation to pre-natal and post-natal exposure among children across China., Methods: Children (3-6 y) (n = 39,782) from randomized day care centres in seven cities in China. Information on pneumonia and pre-natal and post-natal exposure to home environment factors were assessed by a parental questionnaire. Life-time outdoor temperature and GDP per capita were assessed on city level. Associations were calculated by multilevel logistic regression adjusting for fourteen co-variates., Results: Totally 32.0% had ever had pneumonia diagnosed by a physician. Children of farmer mothers (OR = 0.65), with breastfeeding (OR = 0.91) and living in rural (OR = 0.85) or suburban (OR = 0.90) areas had less pneumonia. Buying new furniture one year before conception (OR = 1.11) and after first year of life (OR = 1.10) increased the risk. Redecoration one year before conception (OR = 1.20), during pregnancy (OR = 1.18) and after first year of life (OR = 1.17) increased pneumonia risk. Children with mould (OR = 1.17), window pane condensation (WPC) (OR = 1.20) and mould odour (OR = 1.15) at home at birth only had a higher risk of pneumonia. Similar associations were seen for dampness and mould in the current home. Children in the oldest and newest homes had less pneumonia. Cockroaches (OR = 1.08), mosquitos or flies in the current home (OR = 1.18), an exhaust fan in the bathroom (OR = 1.10) and higher economic development level, measured as GDP per capita on city level (OR 1.11 per 10,000 RMB/year) were associated with childhood pneumonia., Conclusions: Perinatal and postnatal exposure to mould, mould odour and window pane condensation at home can be early life risk factors for childhood pneumonia in China. Moreover, pre-natal and post-natal exposure to chemical emissions from new furniture and renovation could increase the risk of childhood pneumonia. Breastfeeding, farm exposure, and living in rural or suburban areas could be protective., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Background: Pneumonia has been widely recognized as the leading cause of death in children worldwide, but its etiology still remains unclear., Objective: We examined the association between maternal exposure to ambient air temperature during pregnancy and lifetime pneumonia in the offspring., Methods: We conducted a cohort study of 2598 preschool children aged 3-6 years in Changsha, China. The lifetime prevalence of pneumonia was assessed using questionnaire. We backwards estimated each child's exposure to air temperature during prenatal and postnatal periods. Multiple regression model was used to examine the association between childhood pneumonia and exposure to air temperature in terms of odd ratios (OR) and 95% confidence interval (CI)., Results: Prevalence of childhood pneumonia in Changsha was high up to 38.6%. We found that childhood pneumonia was significantly associated with prenatal exposure to air temperature, with adjusted OR (95% CI) = 1.77 (1.23-2.54) for an interquartile range (IQR) increase in temperature, particularly during the second trimester with adjusted OR (95% CI) = 2.26 (1.32-3.89). Boys are more susceptible to the risk of pneumonia due to air temperature than girls. We further observed that maternal exposure to extreme heat days during pregnancy increased the risk of pneumonia in the offspring., Conclusions: Maternal exposure to air temperature during pregnancy, particularly the second trimester, was associated with pneumonia in the children, providing the evidence for fetal origins of pneumonia., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Background: Childhood pneumonia is one of the leading single causes of mortality and morbidity in children worldwide, but its etiology still remains unclear., Objective: We investigate the association between childhood pneumonia and exposure to diurnal temperature variation (DTV) in different timing windows., Methods: We conducted a prospective cohort study of 2,598 children aged 3-6 years in Changsha, China. The lifetime prevalence of pneumonia was assessed by a questionnaire administered by the parents. Individual exposure to DTV during both prenatal and postnatal periods was estimated. Logic regression models was used to examine the association between childhood pneumonia and DTV exposure in terms of odds ratios (OR) and 95% confidence interval (CI)., Results: Lifetime prevalence of childhood pneumonia in preschool children in Changsha was high up to 38.6%. We found that childhood pneumonia was significantly associated with prenatal DTV exposure, with adjusted OR (95%CI) =1.19 (1.02-1.38), particularly during the second trimester. However, childhood pneumonia not associated with postnatal DTV exposure. Sensitivity analysis indicated that boys are more susceptible to the pneumonia risk of diurnal temperature variation than girls. We further observed that the prevalence of childhood pneumonia was decreased in recent years as DTV shrinked., Conclusions: Early childhood pneumonia was associated with prenatal exposure to the diurnal temperature variation (DTV) during pregnancy, particularly in the second trimester, which suggests fetal origin of childhood pneumonia., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

To investigate the role of different pattern of ambient air pollutants exposure during early life on childhood pneumonia, we conducted a retrospective cohort study of 3226 preschool children aged three to six years in Shenzhen, China during 2015 to 2016. Each child's exposure to three main air pollutants (PM10, SO2 and NO2) was calculated by the inverse distance weighted method. Multiple logistic regression analysis was used to investigate the pneumonia risk of early life exposure to air pollution. A relatively high prevalence of pneumonia (24.3%) among preschool children in Shenzhen was significantly associated with exposure to PM10 and SO2 during the first year of life, with adjusted odds ratios = 1.24 (1.05, 1.46) and 1.20 (1.05, 1.38) respectively. However, we observed no relationship between NO2 exposure and childhood pneumonia in pregnancy and first year of life. Sensitivity analysis suggested that boys, younger children (three to four years), non-preterm children, children without parental atopy and with exposure to environmental tobacco smoke were more susceptible to the impact of exposure to PM10 and SO2 on their suffering of pneumonia during their first year of life. Early-postnatal exposure to classical air pollution at low concentration during the first year of life can have an important role in enhancing the risk of childhood pneumonia, especially with the sensitive population. [ABSTRACT FROM AUTHOR]

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Nitrogen dioxide (NO 2) is a widespread air pollutant. Epidemiological evidence indicates that NO 2 is associated with an increase of incidence rate and mortality of asthma, but its mechanism is still unclear. In this study, we exposed mice to NO 2 (5 ppm, 4 h per day for 30 days) intermittently to investigate the development and potential toxicological mechanisms of allergic asthma. We randomly assigned 60 male Balb/c mice to four groups: saline control, ovalbumin (OVA) sensitization, NO 2 alone, and OVA+NO 2 groups. The involved mechanisms were found from the perspective of airway inflammation and oxidative stress. The results showed that NO 2 exposure could aggravate lung inflammation in asthmatic mice, and airway remodeling was characterized by significant thickening of the airway wall and infiltration of inflammatory cells. Moreover, NO 2 would aggravate the airway hyperresponsiveness (AHR), which is characterized by significantly elevated inspiratory resistance (Ri) and expiratory resistance (Re), as well as decreased dynamic lung compliance (Cldyn). In addition, NO 2 exposure promoted pro-inflammatory cytokines (IL-6 and TNF-α) and serum immunoglobulin (IgE) production. The imbalance of Th1/Th2 cell differentiation (IL-4 increased, IFN-γ reduced, IL-4/IFN-γ significantly increased) played a key role in the inflammatory response of asthma under NO 2 exposure. In a nutshell, NO 2 exposure could promote allergic airway inflammation and increase asthma susceptibility. The levels of ROS and MDA among asthmatic mice exposed to NO 2 increased significantly, while GSH levels sharply decreased. These findings may provide better toxicological evidence for the mechanisms of allergic asthma risk due to NO 2 exposure. [Display omitted] • Despite many epidemiological evidence linking NO 2 with asthma, toxicological studies are highly lacking. • NO 2 exposure aggravates the airway inflammatory in mice with allergic asthma by airway remodeling. • Oxidative stress participates in the process of exacerbating asthma through NO 2 exposure. • Our study provides potential toxic mechanisms underlying asthmatic risk of NO 2 exposure. • We suggest avoiding from traffic-related air pollution exposure especially for asthmatic populations. [ABSTRACT FROM AUTHOR]

Background Pneumonia is a common early-childhood respiratory infection that leads to long-term health impacts, but its risk factors remain unclear. Objective To examine the association between early life exposure to both outdoor and indoor air pollution and childhood pneumonia. Methods We conducted a retrospective cohort study of 2598 children aged 3–6 years in Changsha, China (2011-2012). Children's life-time prevalence of pneumonia and exposure to indoor air pollution related to home renovation were surveyed by a questionnaire answered by the parents. Children's exposure to outdoor air pollution, including nitrogen dioxide (NO 2 ), sulfur dioxide (SO 2 ), and particulate matter with an aerodynamic diameter ≤ 10 μm (PM 10 ), was estimated using the measured concentrations at monitoring stations. Association between childhood pneumonia and exposure to indoor and outdoor air pollution during both prenatal and postnatal periods were examined by using logistic regression model in terms of odds ratio (OR) and 95% confidence interval (CI). Results Life-time prevalence of pneumonia in preschool children in Changsha is high, up to 38.6%.We found that childhood pneumonia was associated with postnatal exposure to outdoor particulate air pollutant PM 10 , adjusted OR (95% CI) = 1.26 (1.00–1.57) for per 6 μg/m 3 increase in the concentration. Pneumonia was also associated with postnatal exposure to indoor renovation, adjusted OR (95% CI) = 1.30 (1.02–1.64) for new furniture and 1.30 (1.00–1.69) for redecoration. Combined exposure to outdoor high PM 10 and indoor renovation significantly increased the pneumonia risk. Sensitivity analysis indicated that the association was heterogeneous in different subgroups, but stronger in male and younger children. Conclusion High prevalence of childhood pneumonia in China may be associated with postnatal exposure to ambient particulate air pollution and house renovation. [ABSTRACT FROM AUTHOR]

Pneumonia is the most important cause of child death in the world today. Recent findings suggest that exposure to outdoor air pollutants may increase the pneumonia occurrence, but so far the associations have not been clearly illustrated. Therefore, the effects of outdoor air pollutants and the episode day on childhood pneumonia were investigated by this study. A standardized questionnaire on health, home and environmental factors of 4988 children was conducted in the city of Changsha, China. Average exposure to ambient air pollutants during 2008–2011 was monitored by the air pollution monitoring stations of Changsha Environmental Protection Agency. A two-stage hierarchical regression approach was adopted to estimate the effects of PM10, SO2 and NO2 on pneumonia risk. The prevalence of pneumonia in children aged 3–6 years was 38.2%, which is greatly higher than the developed countries but lower than some developing countries. Furthermore, the increased risk of childhood pneumonia was significantly associated with elevated NO2 concentration (odds ratio (OR) = 1.157, 95% confidence interval (CI): 1.121–1.195) and the episode day (OR = 1.038, 95% CI: 1.024–1.051), but not significantly associated with PM10 and SO2. Exposure to traffic-related air pollution could play an important role in the development of pneumonia in preschool children. The revised National Ambient Air Quality Standards (2012) for NO2 has provided a better control strategy for ambient air quality to reduce the risk of adverse health effects such as pneumonia for children. [ABSTRACT FROM AUTHOR]