Seasonal levels and size fractions of indoor air bioaerosols as predictors of respiratory morbidities among school pupils in Ibadan, Nigeria.

Introduction: Bioaerosols are among pollutants that impair indoor air quality in schools and have been associated with increased respiratory morbidities. Knowledge of bioaerosols' sizes and the likely deposition sites within the child's respiratory tract are essential for the identification of associated risks. This study was designed to determine bioaerosols' size distribution and associated respiratory morbidities among school pupils in Ibadan North Local Government Area (INLGA), Ibadan. Methods: A descriptive cross-sectional study design was adopted. In nine randomly selected public primary schools in INLGA, indoor air sampling (when occupied and unoccupied) was conducted thrice weekly for 3 months each in the wet and dry seasons, respectively. Airborne Bacterial Respirable Fraction (BRF) and Fungal Respirable Fraction (FRF) of aerodynamic diameter of 1.1-4.7 μm which corresponds to regions between the human primary bronchus and the alveolar duct were sampled using a six-stage cascade impactor. The BRF and FRF were estimated and dichotomised into high (>median) and low (≤median) categories. A standardized questionnaire was adapted to elicit information from 554 randomly selected pupils on socio-demographic characteristics and self-reported respiratory morbidities. Data were analyzed using descriptive and inferential statistics at α0.05. Results: Median BRF and FRF during the wet season (2,890 and 283 cfu/m3) were significantly higher than dry season (1,661 and 196 cfu/m3), respectively and above WHO standards. Median BRF and FRF were significantly higher when classrooms were occupied (3,906 and 230 cfu/m3) than unoccupied (2,800 and 214 cfu/m3), respectively. About 67.5% of total bacterial and 77.8% fungal aerosols were respirable fractions. Age of pupils was 10.8 ± 1.35 years and 57.4% were males. Exposure to high BRF and FRF was significantly associated with current rhinitis (aOR = 1.78, 95%CI: 1.11-2.85 and aOR = 1.83, 95%CI: 1.14-2.93) and current wheeze (aOR = 2.77, 95%CI: 1.73-4.43 and aOR = 1.88, 95%CI: 1.18-3.00), respectively. Male pupils were more likely to experience current rhinitis (aOR = 1.09, 95%CI: 1.15-1.58) and current wheeze (aOR = 1.11, 95%CI: 1.22-1.62) than females. Conclusion: Exposure to high levels of respirable bacterial and fungal fractions was associated with respiratory health outcomes among pupils.