Deriving Optimal Mean Indoor Concentration Threshold Levels of PM2.5 and VOC for Detecting Respiratory Symptoms among Pregnant Women in Ndola and Masaiti, Zambia

The burden of air pollution-related morbidity and mortality in developing countries will continue if limited air monitoring and lack of air quality standards continue. This paper focuses on deriving optimal mean indoor threshold concentration levels of particulate matter (PM2.5) and volatile organic compounds (VOCs) for detecting respiratory symptoms among pregnant women in Ndola and Masaiti, Zambia. The study involved 1,170 consenting pregnant women in a cross sectional study using a standard questionnaire. Lung function tests were conducted and indoor PM2.5 and VOCs monitored in houses. Biomass was the main cooking fuel. Indoor air quality monitoring results during cooking and daily average were 501(411, 686) μg/m3 and 393 (303,578) μg/m3 respectively for PM2.5 and 340(318,360) ppb and 343(320, 363) ppb respectively for VOCs. Significant difference in the distribution of PM2.5 (p-value = 0.001) and VOC (p-value = 0.017) between rural and urban area were observed. Mean indoor PM2.5 and VOC varied significantly by cooking activity in both rural (p-value < 0.001) and urban (p-value < 0.001) areas. Similarly, fuel type for PM2.5 at p-value = 0.005 but no significant difference for VOC at p-value = 0.779. However, there was a significant association between mean indoor VOC and forced vital capacity (FVC). Mean indoor PM2.5 was significantly higher in households that presented with respiratory symptoms than those without respiratory symptoms for both rural (p-value = 0.011) and urban areas (p-value < 0.001). Exposing a pregnant woman to mean indoor PM2.5 of 418μg/m3 in rural areas and 372.3μg/m3 in urban areas increased the risk of having at least one respiratory symptom. Statistical significant associations were observed between mean indoor PM2.5 and respiratory symptoms. Household air pollution levels in Zambian homes are high. Therefore, systematic PM and VOCs monitoring is critical in order to develop strategies and policies relating to improvement of air quality and respiratory health.