The Tibetan Plateau is one of the highest regions in the world, exerting profound influence on the large‐scale atmospheric circulation of Asia and the global climate. Here we report ambient concentrations of black carbon (BC), aerosol mass (PM2.5 and PM10) and associated carbonaceous species and water‐soluble inorganic ions from a remote mountain site in the southeastern part of the Tibetan Plateau during spring, in order to characterize the major sources contributing to the ambient aerosol in the background atmosphere of Southeast Asia. Significant build‐up of aerosol and BC concentrations was observed during a dry period, accompanied by the occurrence of fires and transport of pollution from the nearby regions of Southeast Asia and the northern part of the Indian Peninsula. The concentrations of BC, PM2.5 and PM10 mass reached maximum hourly values of 1470 ng m–3, 107 and 117 μg m–3, respectively. Organic carbon (OC), elemental carbon (EC) and sulfate were the predominant aerosol components. OC showed strong correlations with EC (R2= 0.93 for PM2.5 and 0.74 for PM10) and non‐sea‐salt potassium, especially in fine aerosol (R2= 0.95). In addition, the relative change rates of K+ against OC reached characteristically high values, highlighting the important contributions of biomass‐burning smoke.

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Aims/hypothesis Information on the associations of long-term exposure to fine particulate matter (with an aerodynamic diameter less than 2.5 μm; PM 2.5) with the development of type 2 diabetes is scarce, especially for southeast Asia, where most countries are experiencing serious air pollution. This study aimed to investigate the long-term effects of exposure to ambient PM 2.5 on the incidence of type 2 diabetes in a population of Taiwanese adults. Methods A total of 147,908 participants without diabetes, at least 18 years of age, were recruited in a standard medical examination programme between 2001 and 2014. They were encouraged to take medical examinations periodically and underwent at least two measurements of fasting plasma glucose (FPG). Incident type 2 diabetes was identified as FPG ≥7 mmol/l or self-reported physician-diagnosed diabetes in the subsequent medical visits. The PM 2.5 concentration at each participant's address was estimated using a satellite-based spatiotemporal model with a resolution of 1 × 1 km 2. The 2 year average of PM 2.5 concentrations (i.e. the year of and the year before the medical examination) was treated as an indicator of longterm exposure to ambient PM 2.5 air pollution. We performed Cox regression models with time-dependent covariates to analyse the long-term effects of exposure to PM 2.5 on the incidence of type 2 diabetes. A wide range of covariates were introduced in the models to control for potential effects, including age, sex, education, season, year, smoking status, alcohol drinking, physical activity, vegetable intake, fruit intake, occupational exposure, BMI, hypertension and dyslipidaemia (all were treated as timedependent covariates except for sex). Results Compared with the participants exposed to the first quartile of ambient PM 2.5 , participants exposed to the second, third and fourth quartiles of ambient PM 2.5 had HRs of 1.28 (95% CI 1.18, 1.39), 1.27 (95% CI 1.17, 1.38) and 1.16 (95% CI 1.07, 1.26), respectively, for the incidence of type 2 diabetes. Participants who drank occasionally or regularly (more than once per week) or who had a lower BMI (<23 kg/m 2) were more sensitive to the long-term effects of exposure to ambient PM 2.5. Conclusions/interpretation Long-term exposure to ambient PM 2.5 appears to be associated with a higher risk of developing type 2 diabetes in this Asian population experiencing high levels of air pollution.

ABSTRACT1 Research Center for Environmental Changes, Academia Sinica, Taipei, Taiwan, ROC.* Corresponding author address: Dr. Shih-Chieh Hsu, Research Center for Environmental Changes, Academia Sinica, Taipei, Taiwan, ROC; E-mail: schsu@rcec.sinica.edu.tw Ambient aerosols, collected in Taipei in spring 2002, were measured for concentrations of 15 metals (Al, Ca, Na, Mg, K, Ti, Sr, Ba, Mn, Co, Zn, Pb, Cu, Cd, and Sb). Al was used as a mineral aerosol particle indicator, and based on temporal variations of Al concentration, seven Asian dust storm episodes were identified. The fraction of mineral dust in PM 10 was estimated to be around 80% during Asian Dust Storm (ADS) episodes and 15% in non-ADS periods. The metals were categorized into three groups based on their source of origin. The first group consisted of metals from crustal sources, Al, Ca, Sr, Ba, Ti, and Co, the second group was from anthropogenic sources, Pb, Zn, Cd, Cu, and Sb; and the third group was of mixed origins; Na and Mg from sea salt and crustal sources, and K and Mn from crustal and anthropogenic sources. The results of this study demonstrated significant variation in concentrations of metals during spring. Sharp increases in concentration were observed during ADS episodes, particularly for crust-derived elements, Al, Ca, Na, Mg, K, Sr, Ti, Ba, and Co. Metals of anthropogenic origin, Pb, Sb, Cd, and Zn, also increased with ADS episodes, which indicates that significant amounts of pollutant were transported with dust to reach Taiwan. Size-distribution analysis revealed that metals derived from crust and seawater sources (Al, Fe, Sr, Ba, Ti, Na, and Mg) tend to reside in coarse particles, and anthropogenic metals (Pb, Zn, and Cd) in fine particles. Air mass backward trajectory analysis suggested that deserts around Mongolia and the Loess Plateau were the dominant source regions of dust aerosols for ADS. Concentrations of metals in dust were found to change and the wet scavenging affect was strongly indicated. TAO, Vol. 15, No. 5, December 2004 926