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Severe air pollution in the form of smoke haze in the northern part of Southeast Asia (SEA) occurs annually in the dry season due to huge open area burning. Molecular markers of biomass burning were investigated by characterization of fine particles (PM 2.5 ) collected in the dry season (23 February-28 April 2016). The average PM 2.5 , organic carbon (OC) and elemental carbon (EC) concentrations were 64.3 ± 17.6 μg m -3 , 23.6 ± 8.1 μg m -3 and 2.85 ± 0.98 μg m -3 , respectively. SO 4 2- was the dominant species (8.73 ± 2.88 μg m -3 ) of water-soluble ion, followed by NH 4 + (3.32 ± 1.01 μg m -3 ) and NO 3 - (2.70 ± 0.51 μg m -3 ). High concentrations of the biomass burning tracers K + (1.27 ± 0.38 μg m -3 ) and levoglucosan (1.22 ± 0.75 μg m -3 ) were observed. The ratios of levoglucosan/K + (0.92 ± 0.35) and levoglucosan/mannosan (20.4 ± 4.1) identified forest and agricultural waste burning as major contributors to the aerosol. Strong correlations (r > 0.800) between levoglucosan and OC, K + , anhydrosugar isomer (mannosan and galactosan) and other saccharides (mannose, arabitol and mannitol) verified that combustion of biomass was the major source of organic compounds associated with PM 2.5 aerosols. Oxalate was the most abundant (0.75 ± 0.17 μg m -3 ; 53%) of the carboxylates. The concentration of oxalate was strongly correlated to that of PM 2.5 (r = 0.799) and levoglucosan (r = 0.615), indicating that oxalate originates mainly from primary emissions from biomass burning rather than secondary formation from photochemical processes. Backward trajectories indicated that long-range transport air masses influencing air quality in Northern Thailand originated to the west and southwest., (Copyright © 2018. Published by Elsevier B.V.)

A large concentration of finer particulate matter (PM 2.5 ), the primary air-quality concern in northern peninsular Southeast Asia (PSEA), is believed to be closely related to large amounts of biomass burning (BB) particularly in the dry season. In order to quantitatively estimate the contributions of BB to aerosol radiative effects, we thoroughly investigated the physical, chemical, and optical properties of BB aerosols through the integration of ground-based measurements, satellite retrievals, and modelling tools during the Seven South East Asian Studies/Biomass-burning Aerosols & Stratocumulus Environment: Lifecycles & Interactions Experiment (7-SEAS/BASELInE) campaign in 2014. Clusters were made on the basis of measured BB tracers (Levoglucosan, nss-K + , and NO 3 ) to classify the degree of influence from BB over an urban atmosphere, viz., Chiang Mai (18.795°N, 98.957°E, 354m.s.l.), Thailand in northern PSEA. Cluster-wise contributions of BB to PM - ) to classify the degree of influence from BB over an urban atmosphere, viz., Chiang Mai (18.795°N, 98.957°E, 354m.s.l.), Thailand in northern PSEA. Cluster-wise contributions of BB to PM 2.5 , organic carbon, and elemental carbon were found to be 54-79%, 42-79%, and 39-77%, respectively. Moreover, the cluster-wise aerosol optical index (aerosol optical depth at 500nm≈0.98-2.45), absorption (single scattering albedo ≈0.87-0.85; absorption aerosol optical depth ≈0.15-0.38 at 440nm; absorption Ångström exponent ≈1.43-1.57), and radiative impacts (atmospheric heating rate ≈1.4-3.6Kd -1 ) displayed consistency with the degree of BB. PM 2.5 during Extreme BB (EBB) was ≈4 times higher than during Low BB (LBB), whereas this factor was ≈2.5 for the magnitude of radiative effects. Severe haze (visibility≈4km) due to substantial BB loadings (BB to PM 2.5 ≈79%) with favorable meteorology can significantly impact the local-to-regional air quality and the, daily life of local inhabitants as well as become a respiratory health threat. Additionally, such enhancements in atmospheric heating could potentially influence the regional hydrological cycle and crop productivity over Chiang Mai in northern PSEA., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Our research goal was to assess exposure to currently used pesticides among small-scale male farmers residing in two topographically different areas in Chiang Mai Province, Thailand. Farmers (N=136) were recruited from Pong Yaeng subdistrict (N=67) and Inthakhin subdistrict (N=69). Each farmer provided a morning urine void for the analysis of 30 urinary metabolites of insecticides, herbicides, and fungicides. Farmers in Pong Yaeng had significantly higher urinary concentrations of metabolites of organophosphorus insecticides and ethylene bisdithiocarbamates, while farmers from Inthakhin had significantly higher concentrations of malathion, 2,4-D, alachlor, and parathion or EPN metabolites. Based upon the metabolites measured in the urine of the farmers, chlorpyrifos and pyrethroid insecticides seemed to be commonly used across both communities; no significant differences in metabolite concentrations of these insecticides were observed between the two farmer groups. The presence of methamidaphos in the urine of farmers suggests that, despite a ban on its use, methamidaphos continues to be used in the communities. A similar finding with metabolites of methyl parathion must be further investigated. Overall, our results suggest that while each community may use different pesticides, Thai farmers are exposed to a wide variety of pesticides with a broad range in exposure magnitude. Furthermore, age, field size, crop production type, and the use of protective equipment were found to be potential factors influencing the degree of exposure.