Sukonthamut, Sujitra

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Sukonthamut, Sujitra
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sujitra.su@kmitl.ac.th

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    Size Distributions of Inhalable Particulate Matter and Particle-bound Heavy Metals and Their Potential Occupational Health Risk Related to Informal E-waste Recycling in Thailand
    (2022-02-08)
    Keawhanu, Thidarat
    ;
    Sukonthamut, Sujitra
    ;
    Suriyawong, Achariya
    ;
    Junyapoon, Suwannee
    Concentrations and size distributions of atmospheric particulates and particulate-bound heavy metals in different inhalable fractions were studied in working areas during manual dismantling, thermal cutting and cable sheath burning activities. The particulate samples were collected on quartz fiber filters using an eight-stage cascade impactor with flow rate of 28. 3 l min<sup>-1</sup>. Mass concentrations of the particles were measured in each size fraction. Heavy metals bound on the particles were extracted with acid digestion and then analyzed using Atomic Absorption Spectrophotometer. Risk assessment of worker exposure to the particles was determined. The results indicated that the concentrations of ultrafine (d<inf>ae</inf> < 0.43 μm), fine (0.43 < d<inf>ae</inf> < 2.1 μm) and coarse (2.1 < d<inf>ae</inf> < 10 μm) particles were in the ranges of 14.49-62.04, 57.51-120.26 and 153.26–646.99 μg m<sup>−3</sup> during manual dismantling, 363.41-1,011.95, 2,105.40-4,899.11 and 1,698.54-7,075.61 μg m<sup>−3</sup> during thermal cutting and 364.73-1,694.72, 1,953.33-4,431.41 and 1,385.97-6,126.13 μg m<sup>−3</sup> during cable sheath burning, respectively. The concentrations of PM<inf>2.1</inf> and PM<inf>10</inf> released from these activities did not exceed the OSHA PEL threshold limits. Heavy metals adsorbed on the particles (Fe, Cr, Zn, Cu, Pb, Mn) detected during manual dismantling did not exceed the TWA standard. Concentrations of Cr and Pb during cable sheath burning highly exceeded the standards whereas Pb concentrations during thermal cutting slightly exceeded the standard. The heavy metals released from these recycling activities were more enriched on coarse mode than fine mode. Inhalation exposure to Cr, Pb and Mn posed a potential health risk to the workers.
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    Evaluation of nutrient content and antioxidant, neuritogenic, and neuroprotective activities of upland rice bran oil
    (2018-08-01)
    Ruen-ngam, Duangkamol
    ;
    Thawai, Chitti
    ;
    Sukonthamut, Sujitra
    ;
    Nokkoul, Raumjit
    ;
    Tadtong, Sarin
    Upland rice bran is an abundant and valuable antioxidant by-product of rice milling. This study compares the content of γ-oryzanol, γ-tocopherol, and phytochemicals in rice bran oil from 4 varieties of upland rice; Dok-kham (DK), Dok-kha (D), Khem-ngen (KN), and Nang-dam (ND); with that of a conventional variety, Khao Dowk Mali 105 (MA). The extraction was done by shaking rice bran in ethanol in 250 ml flask with a rice bran to a solvent ratio of 1:5 (w/v) at 200 rpm (0.447g) and 30°C in the dark for 30 min. The antioxidant capacity of the extracted oil was evaluated by several methods; DPPH, ferric reducing ability power, and ABTS'<sup>+</sup> assays. The colour of upland rice bran oil was dark from its phenolic and flavonoid contents. The highest contents of γ-oryzanol and γ-tocopherol were found in the bran oil from KN. The highest phytochemical content was found in the bran oil from DK. DK provided the highest antioxidant activity among the varieties mentioned. The neuroprotective and neuritogenic effects of rice bran extracts were also evaluated. D and KN extracts were the best two neuroprotective and neuritogenic extracts because they had the highest contents of γ-oryzanol and colour pigments. Thus Thai rice bran oil has the potential to be an excellent food supplement product due to its high antioxidant contents.