The Health Effects of Air Pollution in Asia: Epidemiologic Studies of Acute and Chronic Effects

Abstract:

In 2004 the Health Effects Institute (HEI) published Special Report 15: Health Effects of Outdoor Air Pollution in Developing Countries of Asia: a Literature Review, the first review of the peer-reviewed Asian literature on the health effects of air pollution, a literature that at that time comprised over 100 studies in 9 countries (HEI 2004). Since then that literature has more than quadrupled in size and now includes coordinated multi-city studies of air pollution and daily mortality conducted as part of the PAPA program. HEI’s upcoming comprehensive review, Outdoor Air Pollution and Health in the Developing Countries of Asia: a Review and Research Needs Assessment, describes the current scope of the Asian literature on the health effects of air pollution, which now includes 421 studies identified through 2007 via HEI’s web-based PAPA-SAN literature survey, and reassesses the Asia time-series studies of short-term exposure to air pollution and daily mortality and morbidity. A companion meta-analysis of Asian studies of the chronic effects of air pollution is in progress and will be published separately in 2009. Time series studies were identified by literature searching procedures developed for the PAPA-SAN and APED systematic review databases and identified over 100 studies published in the peer-reviewed literature as of September 2007. Of these, over 70 studies were suitable for quantitative meta-analysis; a substantial increase over the 28 studies included in HEI’s first meta-analysis. Time-series studies of air pollution have been reported from China, India, Japan, Republic of Korea, Singapore, Malaysia, Taiwan and Thailand, and now include the coordinated multi-city analyses conducted under the PAPA program. Estimated increases in daily mortality and hospital admissions for selected combinations of pollutants and diseases will be presented and compared to previous estimates from Asia, Europe and North America. A 10μg/m3 increase in PM10 was associated with a 0.27% (0.12, 0.42 95% CI) increase in daily mortality based on combining results from 8 Asian studies, an estimate comparable to those from other regions. Analyses will be presented that describe how the estimates vary according to factors such as age and long-term average levels of air pollution. The extent to which the available evidence may have been affected by publication bias (e.g., selective publication by journals of positive results) will also be discussed. The first comprehensive review of Asian studies of the chronic effects of exposure to air pollution is in progress. Using the PAPA SAN data base, 103 studies from 9 countries were identified that estimated effects of exposure on respiratory illness and symptom prevalence, lung cancer, and the pregnancy outcomes low birth weight and pre-term delivery. Preliminary results for selected outcomes, including chronic respiratory symptoms, adverse reproductive outcomes, and lung cancer, will be presented.Implications for health impact assessment of air pollution in Asia will be discussed in light of results of the time-series and chronic effects studies.