Evaluating the effects of atmospheric environment on children’s health in Hanoi, Vietnam

Abstract

Hanoi, Vietnam, has recently been facing several environmental issues including serious air pollution and climate changes, which have been reported as factors affecting child health. The purpose of my research is to evaluate the effect of atmospheric condition on children’s health in Hanoi by examining how short-term changes in daily concentration of ambient air pollutants and weather condition affects the hospital admissions of children younger than 5 years old. The independent variables of the study include daily mean concentration of air pollutants such as particulate matter, nitrogen dioxide (NO2), sulphur dioxide (SO2), carbon monoxide (CO), ozone (O3) and daily meteorological data such as temperature and relative humidity, collected from the national automatic air quality stations. The dependent variables are the daily hospital admissions in children aged less than 5 and were collected from three hospitals in Hanoi.My thesis includes eight chapters which are Introduction (Chapter 1), Methods (Chapter 3), and four studies presented respectively in chapters 2, 4, 5 and 6; a Discussion (Chapter 7) and References (Chapter 8).My first study is a systematic review and meta-analysis on the relationship between air pollution and risk for a specific group of respiratory diseases: wheeze-associated disorders among children in Southeast Asia area. I searched the relevant computerized databases (PubMed, EMBASE, Web of Science, Scopus, and Cochrane library) for indexed publications up to July 2018. Finally, eight studies were qualified for performing a random-effect meta-analysis to compute the pooled effect sizes. The results show that each increase of 10 µg/m3 in concentrations of PM2.5 or PM1 was associated with 1-2% increase in risk of wheeze-associated disorders. Positive associations were found for PM10, SO2, NO2, NOx but no association was found for CO and O3. My study confirmed the strong effect of fine particulate matters on respiratory health and I recommend an updated meta-analysis should be done when more studies are available. A manuscript based on the results from this study has been published in Reviews on Environmental Health in the early of 2019 (Chapter 2).My second study examined the relationship between particulate air pollution and hospital admissions for respiratory diseases by using the time-stratified case-crossover design. The results confirmed that the daily hospital admissions for respiratory diseases among children less than 5 years old in Hanoi were positively associated with the level of airborne particulate matter measured in the city. An increase in 10 μg/m3 of PM10, PM2.5 or PM1 was associated with an increase in risk of admission of 1.4, 2.2 or 2.5% respectively, on the same day of exposure. No significant difference between the effects on males and females was found in the study. These results were published in Science of the Total Environment in 2016 (Chapter 4).In my third study, I applied the time-series approach to examine the association between ambient ozone and hospital admissions for respiratory disease in Hanoi. The results showed that ozone has a stronger effect on the risk of hospital admission for respiratory diseases in both winter and summer. Each increase of 10 µg/m3 of ozone is associated with an increase of 6.2% risk of admission for respiratory disease among children in the winter, and 1.2% in the summer. No significant association was found between ozone and admission for wheeze-associated diseases among children. These results were published in PloSONE in 2018 (Chapter 5).In the last study, I applied the time-series approach to examine the risk of hospitalisation related to hot and cold weather, by age and by causes. I found that a 1 oC decrease in minimum temperature during the cold weather months was associated with 2.2% increase in hospital admission for respiratory infection among children 3-5 years old. A 1 oC increase in diurnal temperature range (DTR) in cold weather was associated with an increase of 1.9% and 1.7% in hospitalisation for all causes and respiratory infection, respectively, among children < 3 years old and an increase of 1.8%, and 3.4% in hospitalisation for all causes and respiratory infection, respectively, among children of 3-5 years old. These results were published in Environmental Science and Pollution Research in 2018 (Chapter 6).My research demonstrated that young children in Hanoi are at increased risk of respiratory admissions due to the high level of air pollution, especially particulate matters and ozone in the city´s ambient air. That means urgent intervention measures are needed to control air pollution to ensure better health protection in Vietnam. In addition, children in Hanoi are also affected by low temperatures in winter. Therefore, clinicians and public health officials need to consider atmospheric environment as risk factors for paediatric respiratory diseases when implementing prevention strategies.