AIR POLLUTANTS IN SCHOOL, URBAN, AND INDUSTRIAL ENVIRONMENTS OF HAWASSA CITY, ETHIOPIA: LEVELS AND POSSIBLE HUMAN HEALTH RISK ASSESSMENT

Abstract

Air pollution has received enormous attention globally due to its detrimental effects on human health, especially on susceptible populations such as children. However, there is scarce data on concentrations and sources of volatile organic compounds (VOCs), inorganic gaseous pollutants (NO2, CO, and SO2), and particulate matter (PM2.5 and PM10) in Ethiopia, particularly Hawassa City. The objective of this PhD work was to determine the indoor and outdoor concentrations of VOCs, PM2.5, PM10, NO2, CO, and SO2 in schools, urban, and industrial environments in Hawassa City, Ethiopia, and evaluate potential health concerns. VOC samples were taken via the passive sampling method using Tenax TA as a sorbent and analyzed using thermal desorption-gas chromatography-mass spectrometry (TD-GCMS). The concentrations of PM10 and PM2.5 were measured using a portable gas monitor device (HoldPeak Laser PM meter, HP 5800D). Levels of NO2, CO, and SO2 were measured using the Aeroqual Series 500 Portable Air Quality Monitor (Aeroqual Ltd., New Zealand). Concentrations of 76 VOCs were determined in air samples from the classrooms and playgrounds of eight primary schools in Hawassa. Concentrations of PM2.5, PM10, NO2, CO, and SO2 were also measured in the outdoor and indoor environments of ten primary schools in Hawassa, Ethiopia. Additionally, indoor and outdoor concentrations of PM2.5, PM10, NO2, CO, and SO2 were measured in urban and industrial areas of Hawassa City, Ethiopia, in the dry and wet seasons. xxiii The highest total VOCs (TVOCs) concentration (83 μg/m3 ) was observed in a classroom of School 2, followed by a classroom of School 1 (76 μg/m3 ), while the smallest TVOC concentration, 37 μg/m3 , was recorded in the playground of School 8. Among the BTEX, toluene was the most dominant in all samples, ranging from 33% in School 4 to 38% in School 1 of ∑BTEX. The I/O ratios of individual VOC in the schools ranged from 0.44 in School 4 to 9.21 in School 2. The highest cumulative cancer risk (CCR×106 ) and the total hazard ratio indicator (THRI) values were 126 and 1.58E-01, respectively, in a classroom of School 4. The concentrations of PM2.5, PM10, and NO2 in the ten primary schools ranged 11–66.3, 30.8–399.7, and 60.5–152 µg/m3 , respectively, and CO and SO2 were not detected in any of the schools. The hazard quotient (HQ) for PM2.5 and PM10 was greater than one in 20% and 50% of the indoor sampling locations, respectively, suggesting moderate risks. The Air Quality Index (AQI) at 40% and 30% of the outdoor sampling sites were unhealthy for sensitive groups due to exposure to PM2.5 and PM10, respectively. The concentrations of PM2.5 and PM10 were found to be above the WHO mean guidelines in 55% and 85% of the sampling sites, respectively, indicating poor quality of the air. In the urban and industrial areas, PM2.5, PM10, and NO2 were detected during both seasons and at all sampling sites. CO was detected during the wet season but not detected at all during the dry season at any of the sites. SO2 was detected only at one site, S17 (ambient of industry 1), during both studied seasons. During the dry season, the average concentrations of PM2.5, PM10, and NO2 ranged from 8.8–310.7, 20.1–515.8, and 40.0– 123.7 µg/m3 , respectively. In the wet season, the ranges for PM2.5, PM10, NO2, and CO levels were 17.2–117.4, 24.3–167.2, 31.8–111.3, and 77–33312 µg/m3 , respectively. xxiv In both the wet and dry seasons, the hazard quotient for PM2.5 and PM10 was greater than one, suggesting a non-carcinogenic effect. The PM2.5 excess lifetime cancer risk ranged from 0.1 to 0.7, which was greater than the recommended range by the WHO and the US EPA, implying a considerable health risk in urban and industrial areas. The CCR and THRI values indicated that the exposure of children to the measured concentrations of benzene may have potentially harmful effects. Additionally, the AQI, HQ values, and concentrations of PM2.5 and PM10 indicated poor air quality in the schools and suggested a significant health risk for all populations around the schools.