Effects of Short-Term Exposure to Air Pollution on Hospital Admissions of Young Children for Acute Lower Respiratory Infections in Ho Chi Minh City, Vietnam
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RESEARCH REPORT HEA L TH HEA L TH Effects of Short-Term Exposure to Air EFFE CTS EFFE CTS Pollution on Hospital Admissions of Young INSTITUTE INSTITUTE Children for Acute Lower Respiratory 101 Federal Street, Suite 500 Infections in Ho Chi Minh City, Vietnam Boston, MA 02110, USA Number 169 +1-617-488-2300 June 2012 HEI Collaborative Working Group on Air www.healtheffects.org Pollution, Poverty, and Health in Ho Chi Minh City (Le Truong Giang, Long Ngo, Sumi Mehta, et al.) RESEARCH REPORT Number 169 June 2012 Effects of Short-Term Exposure to Air Pollution on Hospital Admissions of Young Children for Acute Lower Respiratory Infections in Ho Chi Minh City, Vietnam HEI Collaborative Working Group on Air Pollution, Poverty, and Health in Ho Chi Minh City (Le Truong Giang, Long Ngo, Sumi Mehta, et al.) with a Critique by the HEI Health Review Committee Research Report 169 Health Effects Institute Boston, Massachusetts Trusted Science · Cleaner Air · Better Health Publishing history: This document was posted at www.healtheffects.org in June 2012. Citation for document: HEI Collaborative Working Group on Air Pollution, Poverty, and Health in Ho Chi Minh City. 2012. Effects of Short-Term Exposure to Air Pollution on Hospital Admissions of Young Children for Acute Lower Respiratory Infections in Ho Chi Minh City, Vietnam. Research Report 169. Health Effects Institute, Boston, MA. © 2012 Health Effects Institute, Boston, Mass., U.S.A. Cameographics, Belfast, Me., Compositor. Printed by Recycled Paper Printing, Boston, Mass. Library of Congress Catalog Number for the HEI Report Series: WA 754 R432. Cover paper: made with at least 55% recycled content, of which at least 30% is post-consumer waste; free of acid and elemental chlorine. Text paper: made with 100% post-consumer waste recycled content; acid free; no chlorine used in processing. The book is printed with soy-based inks and is of permanent archival quality. CONTENTS About HEI vii About This Report ix HEI STATEMENT 1 INVESTIGATORS’ REPORT HEI Collaborative Working 5 Group on Air Pollution, Poverty, and Health in Ho Chi Minh City ABSTRACT 5 INTRODUCTION 7 Air Pollution and ALRI 7 Background 7 Evidence from Short-Term Studies 8 Air Pollution, Poverty, and Health 9 Study Location 9 Major Air Pollution Sources in HCMC 9 Pover ty in HCMC 11 SPECIFIC AIMS 12 METHODS 12 Patient Population 12 Respiratory Outcome Data 13 Criteria for ALRI Diagnosis and Hospital Admission 13 Air Quality Data 16 Data Collection and Management 16 Meteorologic Data 17 Assessment of SEP 17 Individual-Level Data on SEP 18 District-Level Data on SEP 19 Statistical Methods 19 Time-Series Analysis 20 Case–Crossover Analysis 20 Effect Modification by SEP 21 RESULTS 21 Hospital Admissions 21 Daily, Monthly, and Seasonal Variations 21 Admissions by ICD-10 Code at Discharge and Patient Demographics 22 Quality Assurance for Hospital Data 24 Air Quality Data 28 Station-Specific Pollutant Concentrations and Correlations 28 Interstation Correlations 28 Citywide Daily Average Concentrations 28 Meteorologic Data 36 Socioeconomic Data 36 Individual-Level Indicator of SEP 36 District-Level Indicator of SEP 39 Research Report 169 STATISTICAL ANALYSES 40 Presentation of Results 40 ALRI Admissions and Pollutant Levels 48 PM10 Results 48 O3 Results 48 NO2 Results 48 SO2 Results 48 Sensitivity Analyses 52 Effect Modification by SEP 55 Individual-Level Indicator of SEP 55 District-Level Indicator of SEP 55 DISCUSSION 57 ALRI Admissions and Pollutant Levels 57 Effect Modification by SEP 57 Case–Crossover vs. Time-Series Analyses 57 Comparison with Other Studies 57 Disease Classifications 58 Averaging Times 58 Seasonal Definitions 58 Differentiating PM10 and. NO2 Effects 58 ACKNOWLEDGMENTS 58 REFERENCES 59 APPENDIX A. HEI Quality Assurance Statement 62 APPENDIX B. Exploring the Potential Influence of RSV as an Unmeasured, Time-Varying Confounder 63 APPENDIX C. Time-Series Results Based on SAS Analyses 68 APPENDIX D. Effect Modification by Indicators of SEP in Time-Series Analyses 70 APPENDICES AVAILABLE ON THE WEB 71 ABOUT THE AUTHORS 71 OTHER PUBLICATIONS RESULTING FROM THIS RESEARCH 72 ABBREVIATIONS AND OTHER TERMS 72 CRITIQUE Health Review Committee 73 INTRODUCTION 73 Role of HEI 73 Scientific Context 74 STUDY DESIGN AND METHODS 74 ALRI Data 74 Air Pollution Data 75 Socioeconomic Information 75 Data Analysis 76 Sensitivity Analysis of Respiratory Syncytial Virus 76 CONTENTS SUMMARY OF RESULTS 76 PM10 Results 78 NO2 Results 78 SO2 Results 78 O3 Results 78 Two-Pollutant Analyses 78 Socioeconomic Indicators 78 RSV Confounding of ALRI Results 79 HEI HEALTH REVIEW COMMITTEE EVALUATION 79 Conduct of the Study 79 Study Results 79 CONCLUSIONS 82 ACKNOWLEDGMENTS 82 REFERENCES 82 Related HEI Publications 85 HEI Board, Committees, and Staff 87 ABOUT HEI The Health Effects Institute is a nonprofit corporation chartered in 1980 as an independent research organization to provide high-quality, impartial, and relevant science on the effects of air pollution on health. To accomplish its mission, the institute • Identifies the highest-priority areas for health effects research; • Competitively funds and oversees research projects; • Provides intensive independent review of HEI-supported studies and related research; • Integrates HEI’s research results with those of other institutions into broader evaluations; and • Communicates the results of HEI’s research and analyses to public and private decision makers. HEI receives its core funds for the Health Effects of Air Pollution program from the U.S. Environmental Protection Agency and the worldwide motor vehicle industry. Frequently, other public and private organizations in the United States and around the world support major projects and research programs. The study by the HEI Collaborative Working Group on Air Pollution, Poverty, and Health in Ho Chi Minh City was supported with funds from HEI’s Public Health and Air Pollution in Asia (PAPA) Program, the Poverty Reduction Cooperation Fund of the Asian Development Bank (Technical Assistance 4714-VIE), and in-kind support from the government of Vietnam. HEI has funded more than 280 research projects in North America, Europe, Asia, and Latin America, the results of which have informed decisions regarding carbon monoxide, air toxics, nitrogen oxides, diesel exhaust, ozone, particulate matter, and other pollutants. These results have appeared in the peer-reviewed literature and in more than 200 comprehensive reports published by HEI. HEI’s independent Board of Directors consists of leaders in science and policy who are committed to fostering the public–private partnership that is central to the organization. The Health Research Committee solicits input from HEI sponsors and other stakeholders and works with scientific staff to develop a Five-Year Strategic Plan, select research projects for funding, and oversee their conduct. The Health Review Committee, which has no role in selecting or overseeing studies, works with staff to evaluate and interpret the results of funded studies and related research. All project results and accompanying comments by the Health Review Committee are widely disseminated through HEI’s Web site (www.healtheffects.org), printed reports, newsletters and other publications, annual conferences, and presentations to legislative bodies and public agencies. vii ABOUT THIS REPORT Research Report 169, Effects of Short-Term Exposure to Air Pollution on Hospital Admissions of Young Children for Acute Lower Respiratory Infections in Ho Chi Minh City, Vietnam, presents a research project supported by HEI and others; it was conducted by the HEI Collaborative Working Group on Air Pollution, Poverty, and Health in Ho Chi Minh City. This report contains three main sections. The HEI Statement, prepared by staff at HEI, is a brief, nontechnical summary of the study and its findings; it also briefly describes the Health Review Committee’s comments on the study. The Investigators’ Report, prepared by the HEI Collaborative Working Group, describes the scientific background, aims, methods, results, and conclusions of the study. The Critique is prepared by members of the Health Review Committee with the assistance of HEI staff; it places the study in a broader scientific context, points out its strengths and limitations, and discusses remaining uncertainties and implications of the study’s findings for public health and future research. This report has gone through HEI’s rigorous review process. When an HEI-funded study is completed, the investigators submit a draft final report presenting the background and results of the study. This draft report is first examined by outside technical reviewers and a biostatistician. The report and the reviewers’ comments are then evaluated by members of the Health Review Committee, an independent panel of distinguished scientists who have no involvement in selecting or overseeing HEI studies. During the review process, the investigators have an opportunity to exchange comments with the Review Committee and, as necessary, to revise their report. The Critique reflects the information provided in the final version of the report. ix HEI STATEMENT Synopsis of Research Report 169 Air Pollution and Ho Chi Minh City Pediatric Hospital Admissions for Acute Lower Respiratory Infections BACKGROUND health, and related issues. Although the studies are In the past decade HEI has made a substantial designed to be achievable within the constraints of commitment to furthering air pollution science in data and technical capacity often found in devel- Asia by funding studies that provide science for oping countries, they are subject to the full peer- decision making as they develop the abilities of review procedures of HEI, which are intended to local scientists to conduct research on air pollution assess the quality and utility of the study. and public health. This report describes a study by The HEI International Scientific Oversight Com- the HEI Collaborative Working Group on Air Pollu- mittee (ISOC) reviewed the Collaborative Working tion, Poverty, and Health in Ho Chi Minh City, Group’s original proposal and provided technical Vietnam, that was financed by HEI, the Poverty expertise and oversight for this project.