Abstract. The Atmospheric Pollution and Human Health in a Chinese Megacity (APHH-Beijing) programme is an international collaborative project focusing on understanding the sources, processes and health effects of air pollution in the Beijing megacity. APHH-Beijing brings together leading China and UK research groups, state-of-the-art infrastructure and air quality models to work on four research themes: (1) sources and emissions of air pollutants; (2) atmospheric processes affecting urban air pollution; (3) air pollution exposure and health impacts; and (4) interventions and solutions. Themes 1 and 2 are closely integrated and support Theme 3, while Themes 1–3 provide scientific data for Theme 4 to develop cost-effective air pollution mitigation solutions. This paper provides an introduction to (i) the rationale of the APHH-Beijing programme and (ii) the measurement and modelling activities performed as part of it. In addition, this paper introduces the meteorology and air quality conditions during two joint intensive field campaigns – a core integration activity in APHH-Beijing. The coordinated campaigns provided observations of the atmospheric chemistry and physics at two sites: (i) the Institute of Atmospheric Physics in central Beijing and (ii) Pinggu in rural Beijing during 10 November–10 December 2016 (winter) and 21 May–22 June 2017 (summer). The campaigns were complemented by numerical modelling and automatic air quality and low-cost sensor observations in the Beijing megacity. In summary, the paper provides background information on the APHH-Beijing programme and sets the scene for more focused papers addressing specific aspects, processes and effects of air pollution in Beijing.

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The inaccurate quantification of personal exposure to air pollution introduces error and bias in health estimations, severely limiting causal inference in epidemiological research worldwide. Rapid advancements in affordable, miniaturised air pollution sensor technologies offer the potential to address this limitation by capturing the high variability of personal exposure during daily life in largescale studies with unprecedented spatial and temporal resolution. However, concerns remain regarding the suitability of novel sensing technologies for scientific and policy purposes. In this paper we characterise the performance of a portable personal air quality monitor (PAM) that integrates multiple miniaturised sensors for nitrogen oxides (NO x ), carbon monoxide (CO), ozone (O 3 ) and particulate matter (PM) measurements along with temperature, relative humidity, acceleration, noise and GPS sensors. Overall, the air pollution sensors showed high reproducibility (mean R 2 = 0.93, min-max: 0.80-1.00) and excellent agreement with standard instrumentation (mean R 2 = 0.82, min-max: 0.54-0.99) in outdoor, indoor and commuting microenvironments across seasons and different geographical settings. An important outcome of this study is that the error of the PAM is significantly smaller than the error introduced when estimating personal exposure based on sparsely distributed outdoor fixed monitoring stations. Hence, novel sensing technologies such as the ones demonstrated here can revolutionise health studies by providing highly resolved reliable exposure metrics at a large scale to investigate the underlying mechanisms of the effects of air pollution on health.

Current indoor air quality (IAQ) guidelines in school buildings are framed around thermal conditions, carbon dioxide (CO 2 ) levels and corresponding ventilation rates without considering specific indoor pollution levels. Drawing on detailed monitoring data from a sample of 18 classrooms from six London schools, the aim of this paper is to highlight behavioural and environmental factors that affect pollution levels in classrooms, and evaluate the adequacy of CO 2 as an overall predictor for IAQ using multilevel modelling. Together with elimination of indoor emission sources, keeping the temperatures below 26 C, and preferably below 22 C depending on season, may limit total volatile organic compounds below thresholds associated with sensory irritations. The models suggested that after removing dust reservoirs from the classrooms, lowering average indoor CO 2 levels below 1000 ppm by increasing ventilation rates can limit indoor airborne particulate matter concentrations below recommended annual WHO 2010 guidelines. Uncontrolled infiltration rates may increase indoor NO 2 levels and microbial counts of fungal and bacterial groups, whose presence is associated with wet and moist materials. Overall, indoor CO 2 levels were a useful proxy for indoor investigations as they can prevent overheating, dilute pollutants with indoor sources and purge concentrations of airborne particles; however, they were a poor predictor of traffic related pollutants. Practical implications of the findings on the UK policy and building design industry are discussed. Practical application: Driven by the growing population, and many years of intensive use, the UK building stock is in need of rapid expanding, extensive refurbishment and maintenance. However, local authorities lack the money for comprehensive and specialist renovations. The recommendations presented in this paper take into account specific needs and possibilities, and target building designers, Downloaded from engineers and occupants involved with daily operation and management of school buildings. Timely control of ventilation and heating systems, informed selection of construction materials, interior finishing and elimination of indoor sources may improve IAQ of school classrooms.

Rationale: Exacerbations are key events in chronic obstructive pulmonary disease (COPD), affecting lung function decline and quality of life. The effect of exposure to different air pollutants on COPD exacerbations is not clear. Objectives:To carry out a systematic review, examining associations between air pollutants and hospital admissions for COPD exacerbations.Methods: MEDLINE, Embase, BIOSIS, Science Citation Index, and the Air Pollution Epidemiology Database were searched for publications published between 1980 and September 2015. Inclusion criteria were focused on studies presenting solely a COPD outcome defined by hospital admissions and a measure of gaseous air pollutants and particle fractions. The association between each pollutant and COPD admissions was investigated in metaanalyses using random effects models. Analyses were stratified by geographical clusters for investigation of the consistency of the evidence worldwide.Measurements and Main Results: Forty-six studies were included, and results for all the pollutants under investigation showed marginal positive associations; however, the number of included studies was small, the studies had high heterogeneity, and there was evidence of small-study bias. Geographical clustering of the effects of pollution on COPD hospital admissions was evident and reduced heterogeneity significantly. Conclusions:The most consistent association was between a 1-mg/m 3 increase in carbon monoxide level and COPD-related admissions (odds ratio, 1.02; 95% confidence interval, 1.01-1.03). The heterogeneity was moderate, and there was a consistent positive association in both Europe and North America, although levels were clearly below World Health Organization guideline values. There is mixed evidence on the effects of environmental pollution on COPD exacerbations. Limitations of previous studies included the low spatiotemporal resolution of pollutants, inadequate control for confounding factors, and the use of aggregated health data that ignored personal characteristics. The need for more targeted exposure estimates in a large number of geographical locations is evident.

<p><strong>Abstract.</strong> APHH-Beijing (Atmospheric Pollution and Human Health in a Chinese Megacity) is an international collaborative project to examine the emissions, processes and health effects of air pollution in Beijing. The four research themes of APHH-China are: (1) sources and emissions of urban atmospheric pollution; (2) processes affecting urban atmospheric pollution; (3) exposure science and impacts on health; and (4) interventions and solutions to reduce health impacts. Themes 1 and 2 are closely integrated and support Theme 3, while Themes 1–3 provide scientific data for Theme 4 on the development of cost-effective solutions. A key activity within APHH-Beijing was the two month-long intensive field campaigns at two sites: (i) central Beijing, and (ii) rural Pinggu. The coordinated campaigns provided observations of the atmospheric chemistry and physics in and around Beijing during November–December 2016 and May–June 2017. The campaigns were complemented by numerical air quality modelling and air quality and meteorology data at the 12 national monitoring stations in Beijing. This introduction paper provides an overview of (i) APHH-Beijing programme, (ii) the measurement and modelling activities performed as part of it in Beijing, and (iii) the air quality and meteorological conditions during the two field campaigns. The winter campaign was characterized by high PM<sub>2.5</sub> pollution events whereas the summer experienced high ozone pollution events. Air quality was poor during the winter campaign, but less severe than in the same period in 2015 when there were a number of major pollution episodes. PM<sub>2.5</sub> levels were relatively low during the summer period, matching the cleanest periods over the previous five years. Synoptic scale meteorological analysis suggests that the greater stagnation and weak southerly circulation in November/December 2016 may have contributed to the poor air quality.</p>

The aim of this paper is to investigate whether keeping indoor thermal conditions and carbon dioxide (CO 2 ) levels within the current guideline values can provide a healthy and comfortable school environment. The study was organised as a longitudinal investigation over an academic year using a cohort of 376 students aged 9 to 11 (response rate: 87%) attending 15 classrooms in five London primary schools. The prevalence of asthmatic symptoms and asthma attacks was significantly higher among children attending urban schools (10.2%) than suburban schools (1.5%), and was significantly related to exposure to higher nitrogen dioxide (NO 2 ) concentrations (odds ratio: 1.11, 95% confidence interval: 1.00-1.19). Selfreported dermal, mucosal, respiratory and general symptoms were 18.5%, 60.7%, 28.2% and 43.6% respectively in the heating season, and decreased in the non-heating season. Infiltration rates were negatively associated with prevalence and incidence of all sick building syndrome symptoms. Exposure to traffic-related pollutants, such NO 2 , ozone (O 3 ) and tetrachloroethylene (T4CE), associated with mucosal symptoms, also increased dissatisfaction with indoor air quality (IAQ) and, therefore, perceived IAQ might be a first indication of exposure. Among targeted microbial counts, only Trichoderma viride remained significant predictors of satisfaction with IAQ even at low concentrations. The study provides evidence that simultaneous provision for limiting indoor CO 2 levels and thermal conditions below current guidelines (e.g. below 1000 ppm and 26 C or 22 C depending on season) may improve perceived IAQ. This paper stresses the need to go beyond current regulations to investigate concentrations of specific pollutants to ensure a healthy school environment, and closes with a section on the practical implications on the UK policy and the building design industry.