Vulnerability to Environmental Exposure in the Context of Air Pollution Changes and Daily Out-Patient Visits in Chiang Mai, Thailand

Abstract

Compared to the developed countries of North America and Europe, few studies have been conducted on the effects of air pollution on daily morbidity (hospital visits/admissions) in developing countries, particularly in Southeast Asia with its tropical climate. This study aims to identify those groups of people who are more susceptible to daily changes in air pollution in a developing, tropical country such as Thailand.
Generalised negative binomial regression was used to assess the short-term effects of air pollution (SO2, NO2, CO, O3, PM10, and PM2.5) on daily outpatient visits (all-cause and respiratory: ICD-10 J00-J99) in Chiang Mai from 2002 to 2006, controlling for seasonality and potential confounders. Lag effects of exposure and modification by age, sex, and occupation were also examined. The results showed that the effects of SO2 were higher than other pollutants (using wide CIs), with higher all-cause visits among the elderly (11.8% increase, 95% CI: -4.2 to 30.5), males (6.3% increase, 95% CI: -7.8 to 22.4), and manual workers (31.2% increase, 95% CI: 4.4 to 64.9) per 10ppb increase in SO2. Despite no statistical significant difference being observed in morbidity risk between subgroups, the elderly seemed to be more vulnerable to daily changes in air pollution than other groups. It is recommended therefore that public health interventions be targeted at this group of people.