Original scientific article ■ © Inštitut za sanitarno inženirstvo, 2015 Methodology for defining the effects of outdoor air pollution on children's health at the population level - a systematic review An GALIČIČ12, Lijana ZALETEL-KRAGELJ32, Marija Zlata BOŽNAR4, Boštjan GRAŠIČ4, Primož MLAKAR4, Andreja KUKEC32* Received: 30.10.2015 Accepted: 20.11.2015 1 University of Ljubljana, Faculty of Health Sciences, Department of Sanitary Engineering, Zdravstvena 5, SI-1000 Ljubljana 2 National Institute of Public Health of Slovenia, Trubarjeva 2, SI-1000 Ljubljana 3 University of Ljubljana, Faculty of Medicine, Public Health Centre, Zaloška 4, SI-1000 Ljubljana 4 MEIS storitve za okolje d.o.o., Mali Vrh pri Šmarju 78, SI-1293 Šmarje - Sap * Corresponding author Assist. prof., PhD. Andreja Kukec, dipl. san. inž. Public Health Centre, Faculty of Medicine University of Ljubljana Zaloška 4, Ljubljana, Slovenia e-mail: andreja.kukec@mf.uni-lj.si ABSTRACT Outdoor air pollution is an important determinant of health. Children are one of the most sensitive population groups due to their yet underdeveloped respiratory system. Methodology for linkage environmental and health data at population level had been initiated by the World Health Organization about twenty years ago. The aim of our study is an overview of methods with which the effects of outdoor air pollution on children's health have been investigated at the population level. Literature overview was made systematically. Health effects of outdoor air pollution at the population level were firstly investigated after 1990. Simultaneously with the most common outdoor air pollutants (NO2, SO2, O3, PM10 and CO) monitoring of health effects was measured. Poisson regression analysis was the most frequently used method of ecological time-series studies and spatial studies. Exposure misclassification was in this research field the most common limitation of ecological studies. This study supports the need of future research on outdoor air pollution's effects on the at population level from an engineering and public health view. Key words: outdoor air pollution, children health, time-series study, spatial study, methodology Vol. 9 No. 1/2015 International Journal of Sanitary Engineering Research 35 A. Galicic, L. Zaletel-Kragelj, M. Zlata Boznar et al. I Methodology for defining the effects of outdoor air pollution on children's health at the population level.. INTRODUCTION In Europe in 2012 482,000 people died of outdoor air pollution-related causes. Outdoor air pollution occurs when the concentration of pollutants in air exceeds the level which has adverse health effects or adverse effects on environment [1]. In average, people daily breathe between 10 to 20 m3 of air, depending on their physical constitution and physical activity [2, 3]. Excessive outdoor air pollution represents a health hazard for population [4]. One of the first evidences of adverse health effects of air pollution at the population level is so called the Great Smog during December 1952 in London. Thousands of people have died because of the high levels of sulphur dioxide (SO2) and particles of different diameter present in outdoor air. The main reason for the incident was associated with temperature inversion which had trapped (and formed a thick layer of) SO2 and smoke. Since then many epidemiological studies have confirmed that short-term exposure to outdoor air pollution is connected with morbidity and mortality [5]. There are about 200 different pollutants present in urban outdoor air. The most common outdoor air pollutants are particulate matter of different diameters, ozone (O3), nitrogen oxides (NOx), sulphur dioxide (SO2), carbon monoxide (CO), heavy metals, volatile organic compounds and pesticides [6]. Both short- and long-term exposure is associated with high risk of respiratory and heart diseases, stroke and lung cancer. The exposure has stronger effect on children, elderly, poor and ill [1]. Outdoor air pollution is strongly associated with chronic respiratory diseases which often appear in childhood. Asthma and other lower respiratory system diseases are in children strongly associated with exposure to NO2, SO2 and PM10 [7-9]. Outdoor air pollution is also associated with daily visit of primary care health system and hospital admissions [10-14]. The association between outdoor air pollution and its effects on human health can be examined at the individual or at the population level [15, 16]. Studies at the population level were firstly initiated by the World Health Organization (WHO) about twenty years ago, when the usage of so called "linkage methods for environment and health analysis" was recommended [17, 18] as a useful tool in determining the association between environmental pollution and its health effects. Time-trend studies are studies that compare disease rates over time in one population (Morgenstern, 1982; Morgenstern and Thomas, 1993). Spatial studies, usually referred to as multi-group studies, are studies that compare disease rates among many spatial units during the same period [19, 20]. The aim of our systematic review is an overview of methods of epidemiological studies with which the effects of outdoor air pollution on children's health have been investigated at the population level. The specific goal of this review is the presentation of the progress in new findings of the effects of outdoor air pollution on children's health. For 36 © Institut za sanitarno inzenirstvo, 2015 Methodology for defining the effects of outdoor air pollution on children's health at the population level... rn A. Galicic, L. Zaletel-Kragelj, M. Zlata Boznar et al. this purpose the overview of scientific articles on this field was made, with the emphasis on methods of defining the association between pollution and effect health effects at population level with the view of the opportunity for future research. METHODS Overview of articles on the topic of outdoor air pollution's effects on children's health was arranged chronologically in database PubMed Central. Overview of articles was made in four steps. In each next step new inclusion and exclusion criteria were added. In the first step we included original and review scientific articles in English language with free full text available and with the publication date between January 1st 1977 (publication year of first article on this topic) and October 17th 2015. In the second step we have excluded the articles which did not include the topic of outdoor air pollutions effect's on children's health. In the third step articles were divided into the groups depending on study design. In the last, fourth step epidemiological ecological studies were analysed precisely. Observed health outcome, exposure to outdoor air pollution and methods of defining the association between outdoor air pollution and health effects at the population level are displayed in tabular form. In databases epidemiological ecological studies that were made in Slovenian area were looked for, the results of this search is also displayed in tabular form (Figure 1). c \ Q. 1 CD -t—» CO -L 144 articles \ CL n CD J / CO L_ V y 38 excluded on the first step 106 articles Q_ CD -t—» CO 3 76 excluded on the second step 30 articles o_