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Abstract Background Nitrogen dioxide (NO 2) is a typical indicator of traffic-related air pollution, and few studies with exposure assessment of high resolution have been conducted to explore its association with preterm birth in China. Objectives To investigate the association between NO 2 exposure based on a land use regression (LUR) model and preterm birth in Shanghai, China. Methods A retrospective cohort study was performed among 25,493 singleton pregnancies in a major maternity hospital in Shanghai, China, from 2014 to 2015. A temporally adjusted LUR model was used to predict the prenatal exposure to NO 2 based on residence address of each gravida. Logistic regression was performed to evaluate the associations of ambient NO 2 exposure with preterm birth during six exposure periods, including the entire pregnancy, the first trimester, the second trimester, the third trimester, the last month, and the last week before delivery. Sensitivity analysis with a matched case-control design was conducted to test the robustness of the association between NO 2 exposure and preterm birth. Results The average NO 2 concentrations during the entire pregnancy was 48.23 µg/m3 among all participants. A 10 µg/m3 increase in NO 2 concentrations was associated with preterm birth, with an adjusted odds ratio of 1.03 (95% confidence interval [CI]: 0.96,1.10) for exposures during the entire pregnancy, 1.00 (95%CI: 0.95,1.06) in the first trimester, 1.01 (95%CI: 0.96,1.07) in the second trimester, 1.07 (95%CI: 1.02,1.13) in the third trimester, 1.10 (95%CI: 1.04,1.15) and 1.05 (95%CI: 1.00,1.09) in the month and week before delivery, respectively. The results of the matched case–control analysis were generally consistent with those of main analyses. Conclusion NO 2 may increase the risk of preterm birth, especially for exposures during the third trimester, the month and the week before delivery in Shanghai, China. Graphical abstract fx1 Highlights • The first study evaluating the impacts of LUR-derived NO 2 on preterm birth in China. • The LUR model of NO 2 has a high spatial resolution and predictive ability. • The impacts of NO 2 exposure on preterm birth varied by different trimesters. • NO 2 exposure during the third trimester may increase the risk of preterm birth. [ABSTRACT FROM AUTHOR]

Source apportionment of fine particulate matter (PM 2.5) components is crucial for air pollution control. Prediction accuracies by the chemical transport model (CTM) significantly affect source apportionment results. Many efforts have been made to improve source apportionment results based on the CTM using mathematical algorithms, but the reasons for uncertainties in source apportionment results are less concerned. Here, an integrated optimization methodology is developed to quantify deviations from emission inventory and chemical mechanism in the model for improving prediction and source apportionment accuracies. Emission deviations of primary aerosols and gaseous pollutants are firstly calculated by an optimization algorithm with observation and receptor model constraints. Emission inventory is then adjusted for a new CTM simulation. Deviations from chemical mechanism for secondary conversions are evaluated by biases between observations and new predictions. Source apportionment results are adjusted according to both emission and chemical mechanism deviations. A winter month in 2016 at the Qingpu supersite in eastern China is selected as a case study. Results show that our integrated optimization methodology can successfully adjust emissions to pull original predictions towards observations. Total deviations of emissions for elemental carbon, organic carbon, primary sulfate, primary nitrate, primary ammonium, sulfur dioxide (SO 2), nitrogen oxides (NO x) and ammonia (NH 3) are estimated +59.6%, +95.9%, +72.9%, +82.2%, +75.9%, −6.4%, +67.6% and −17.6%, respectively. Also, major directions of deviations from chemical mechanisms can be captured. Deviations from SO 2 to secondary sulfate, nitrogen dioxide (NO 2) to secondary nitrate and NH 3 to secondary ammonium conversions are estimated −77.3%, +27.1% and −38.8%, respectively. Consequently, source apportionment results are significantly improved. This developed methodology provides an efficient way to quantify deviations from emissions and chemical mechanisms to improve source apportionment for air pollution management. [Display omitted] • An integrated methodology is developed to improve source apportionment results of CTM. • Deviations of regional emission inventory can be quantified through the methodology. • The methodology was also able to adjust the bias of implemented chemical mechanisms. [ABSTRACT FROM AUTHOR]

Findings for impacts of outdoor air pollutants on birth outcomes were controversial. We performed a retrospective observational study in 2527 preschoolers of Shanghai, China and investigated associations of duration-averaged concentrations of outdoor sulphur dioxide (SO 2), nitrogen dioxide (NO 2), and particulate matter with an aerodynamic diameter ≤ 10 μm (PM 10) in different months and trimesters of gestation, with preterm birth (PB), low birth weight (LBW), term low birth weight (T-LBW), and small for gestational age (SGA). Daily concentrations of outdoor air pollutants were collected in each residence-located district. Parents reported health information. In the multivariate logistic regression analyses, exposures to outdoor NO 2 were consistently associated with the higher odds of LBW and T-LBW. These associations were generally stronger for early months than for later months of the gestation. Adjusted odds ratios generally were larger in multi-pollutant model than in single-pollutant model. Exposure to NO 2 in the first month of the gestation was significantly associated with T-LBW (adjusted OR, 95%CI: 1.91, 1.02–3.58 for increment of interquartile range (18.5 μg/m3); p -value = 0.044) in multi-pollutant model. This association was stronger in girls, renters, and children whose mothers ≥30 years-old, with household dampness-related exposures, and with parental smoking during pregnancy. Our results indicate that exposure to NO 2 during gestation perhaps is a risk factor for LBW and T-LBW, and effects of NO 2 exposures could be greater during early periods than during later periods of gestation. • A retrospective observational study in 2527 preschoolers was conducted. • Exposures to outdoor NO 2 consistently associated with LBW and T-LBW. • These associations were stronger for early months than for later months. • Adjusted ORs were larger in multi-pollutant than single-pollutant model. • No significant associations were found of SO 2 and PM 10 with all outcomes. [ABSTRACT FROM AUTHOR]