We measured levels of VOCs and determined the distributions of benzene concentrations over the area of two petrol stations in all three seasons. Using the concentrations and sampling positions, we created isoconcentration contour maps. The average concentrations ranged 18-1288 μg m(-3) for benzene and 12-81 μg m(-3) for toluene. The contour maps indicate that high-level contours of benzene were found not only at the fuel dispenser areas but also at the storage tank refilling points, open drainage areas where gasoline-polluted wastewater was flowing, and the auto service center located within the station area. An assessment of the benzene to toluene ratio contour plots implicates that airborne benzene and toluene near the fuel dispenser area were attributed to gasoline evaporation although one of the studied stations may be influenced by other VOC sources besides gasoline evaporation. Additionally, during the routine refilling of the underground fuel storage tanks by a tank truck, the ambient levels of benzene and toluene increased tremendously. The implementation of source control by replacing old dispensers with new fuel dispensers that have an efficient cutoff feature and increased delivery speed can reduce spatial benzene concentrations by 77%. Furthermore, a questionnaire survey among 63 service attendants in ten stations revealed that headache was the most reported health complaint with a response rate of 32%, followed by fatigue with 20%. These prominent symptoms could be related to an exposure to high benzene concentrations.
Formaldehyde is commonly used in embalming solution in medical fields to preserve tissues. Formaldehyde vapor released from cadavers during dissection practice can adversely affect students and instructors in gross anatomy laboratories. Therefore, this study investigated formaldehyde concentrations in a gross anatomy laboratory of Mahasarakham University, Thailand. Area-based sampling was conducted for three scenarios: (1) a laboratory cleaning period, (2) three periods of teaching classes and (3) a non-teaching class period. Personal samples were also collected for five consecutive working days from two anatomy lab instructors and a non-lab instructor. Measurements were conducted during May to October 2016 using cartridges filled with dinitrophenylhydrazine coated silica gel. Samples were desorbed and analyzed by high performance liquid chromatography. Results showed that the average area-based concentrations during the dissection classes ranged from 9.3 to 17.6 ppb, while the non-teaching class concentration was 5.5 ppb. The concentration increased to 3.1×103 ppb during the laboratory cleaning. The five-day average exposure concentrations were 7.6 ppb and 4.7 ppb for the two lab instructors and 1.1 ppb for the non-lab instructor. The lifetime cancer risk estimates were 5.8×10-6, 2.9×10-6 and 8.1×10-7, respectively. The three most reported clinical symptoms by the gross anatomy students were associated with formaldehyde concentrations above 16 ppb at the significance level of 0.05. These included unpleasant odor, general fatigue or fatigue after awakening and dizziness with response rates of 57.5 %, 38.5 % and 33.1 %, respectively. Improvement of the ventilation and source control measures are essential for reducing formaldehyde emissions in the gross anatomy laboratory.
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