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Several studies in North American cities have reported associations between air pollution and respiratory symptoms. Replicating these studies in cities with very different population and weather characteristics is a useful way of addressing uncertainties and strengthening inferences of causality. To this end we examined the responses of three different panels to particulate matter (PM) air pollution in Bangkok, Thailand, a tropical city characterized by a very warm and humid climate. Panels of schoolchildren, nurses, and adults were asked to report daily upper and lower respiratory symptoms for 3 months. Concentrations of daily PM(10) (PM with a mass median aerodynamic diameter less than 10 microm) and PM(2.5) (airborne particles with aerodynamic diameters less than 2.5 microm) were collected at two sites. Generally, associations were found between these pollution metrics and the daily occurrence of both upper and lower respiratory symptoms in each of the panels. For example, an interquartile increase of 45 microg/m(3) in PM(10) was associated with about a 50% increase in lower respiratory symptoms in the panel of highly exposed adults, about 30% in the children, and about 15% in the nurses. These estimates were not appreciably altered by changes in the specification of weather variables, stratification by temperature, or inclusion of individual characteristics in the models; however, time trends in the data cause some uncertainty about the magnitude of the effect of PM on respiratory symptoms. These pollutants were also associated with the first day of a symptom episode in both adult panels but not in children. The estimated odds ratios are generally consistent with and slightly higher than the findings of previous studies conducted in the United States.

This paper studies the relevance between carbon dioxide (CO2) absorption rates of common trees in Chulalongkorn University (Thailand), and environmental factors -- light intensity, air temperature, leaf temperature, and CO2 concentration in air -- by forming non-linear models. The common tree species are Pterocarpus indicus, Samanea saman, Peltophorum pterocarpum, and Terminalia catappa. Measuring CO2 absorption was done by chamber analysis approach. The experiment was carried out by gauging 10 leaves, 7 hours per day, and 2 days per species. According to the models, it is obvious that light intensity is the most influential factor to CO2 absorption for all studied species. Peltophorum pterocarpum and Samanea saman reach their maximum CO2 uptake rates of 24.5 and 20.9 CO2 µmol m-2s-1, when photosynthetically active radiation is 1100 and 1500 µmol m-2s-1 respectively. The other two do not reach their maximum rate within model data range. The regressions were best fitted with Gaussian function and Sigmoidal function. It is also suggested that Peltophorum pterocarpum and Samanea saman are good carbon sink and they should be planted more in the city for optimal CO2 absorption.