Measurement of indoor and outdoor SO2 and NO2 and indoor BTEX/VOC concentrations at pre-schools in Mabopane Township, Tshwane Metropolitan Municipality, Gauteng Province, South Africa

Abstract

Introduction: Children spend approximately 7 hours a day at pre-schools, mostly indoors. The aim of the study was to assess indoor and outdoor SO2 and NO2 and indoor BTEX/VOC at pre-schools situated in Mabopane, Tshwane Metropolitan Municipality, Gauteng Province, South Africa Methodology: Six pre-schools in the study area were purposively selected to participate in the study. Indoor and outdoor levels of SO2 and NO2, and indoor BTEX/VOC were assessed over 24hrs for two weeks using Radiello passive samplers. Indoor temperature and relative humidity were also monitored using temperature data loggers. The outdoor temperature and relative humidity data was provided by South African Weather Services. Results: The indoor and outdoor SO2 median levels were 0.22 μg.m-3 and 1.12 μg.m-3 The indoor and outdoor NO2 median levels were 21.10 μg.m-3 and 17.22 μg.m-3, respectively. The indoor/outdoor ratios for NO2 and SO2 were 0.20 and 1.07, respectively. The infiltration factor parameter estimates of NO2 and SO2 were 0.48 and 0.01. The indoor and outdoor temperature and relative humidity levels were 2.11 °C and 22.4 °C, and 43.14% and 57%. The median concentrations of BTEX ranged from 0.5µg/m3 to 43.19µg/m3. The Kruskal-Wallis test showed that the level of benzene in the six schools differed significantly - χ^2=13.87,p-value=0.016. The levels of toluene at the six school did not differ significantly - χ^2=5.96,p-value=0.310. There was no statistically significant difference between the six schools in terms of ethylbenzene - χ^2=6.30,p-value=0.2710. The p-value for Xylene showed there was no statistically significant difference between the six schools - χ^2=6.01,p-value=0.2967.. Conclusion: The levels of outdoor NO2, SO2 and BTEX/VOC were below the South African National Ambient Air Quality Standards and WHO Air Quality Guidelines. However, they still pose a health risk for children attending pre-school in the area. Keywords: Air pollution; SO2, NO2, BTEX/VOC, Temperature; Relative humidity; South African