Background: To explore the inflammation phenotypes following indoor pollutants exposure based on marker expression on eosinophils and neutrophils with the application of chemometric analysis approaches. Methods: A cross-sectional study was undertaken among secondary school students in eight suburban and urban schools in the district of Hulu Langat, Selangor, Malaysia. The survey was completed by 96 students at the age of 14 by using the International Study of Asthma and Allergies in Children (ISAAC) and European Community Respiratory Health Survey (ECRHS) questionnaires. The fractional exhaled nitric oxide (FeNO) was measured, and an allergic skin prick test and sputum induction were performed for all students. Induced sputum samples were analysed for the expression of CD11b, CD35, CD63, and CD66b on eosinophils and neutrophils by flow cytometry. The particulate matter (PM2.5 and PM10), NO2, CO2, and formaldehyde were measured inside the classrooms. Results: Chemometric and regression results have clustered the expression of CD63 with PM2.5, CD11b with NO2, CD66b with FeNO levels, and CO2 with eosinophils, with the prediction accuracy of the models being 71.88%, 76.04%, and 76.04%, respectively. Meanwhile, for neutrophils, the CD63 and CD66b clustering with PM2.5 and CD11b with FeNO levels showed a model prediction accuracy of 72.92% and 71.88%, respectively. Conclusion: The findings indicated that the exposure to PM2.5 and NO2 was likely associated with the degranulation of eosinophils and neutrophils, following the activation mechanisms that led to the inflammatory reactions.

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A cross-sectional study of 470, 14-year-old students from 8 secondary schools located in suburban and urban areas in Hulu Langat district, Selangor, Malaysia was undertaken to determine the impact of atmospheric indoor air pollutants on atopy, asthma, respiratory symptoms and lung inflammation among school children. The students were surveyed using ISAAC and ECRHS questionnaires, their FeNO levels were measured and allergic skin prick tests were conducted. Active and passive sampling was used to measure the classroom indoor air concentration of NO 2 , CO 2 , formaldehyde, PM 10 , PM 2.5 , temperature and relative humidity. Linear mixed model, two-levels multiple logistic regression, PCA and SPC were applied to determine the complex relationship between respiratory symptoms, personal factors, FeNO levels and atmospheric indoor pollutants. 20.6% of students reported daytime breathlessness and 55.5% reported having rhinitis in the last 12 months. Atopy was prevalent in 57.7% of students, with predominant sensitization to Derp1 (51.9%) and Derf1 (47.9%) among doctor's diagnosed asthmatic students. Indoor air pollutants in urban area schools were significantly higher than those in suburban areas (p < 0.001). There was a significant association between exposure to PM 10 (OR = 2.66, 95% CI: 1.33-5.30) with skin allergy symptoms in the past 12 months. The PCA suggested that the most prominent factor associated with increasing FeNO levels was PM 10 , with 73.5% of the variation. SPC predicted the pattern of FeNO at an upper confidence limit (UCL) of 104.21 ppb with increasing PM 10 concentration in the classroom (UCL = 40.23 µg m-3). Exposure to PM 10 and PM 2.5 significantly influenced the inflammation of the school children's lungs. Moreover, there were associations between self-reported wheezing, daytime and nocturnal attack of breathlessness with doctor's diagnosed asthma among school children.

Numerous epidemiological studies have evaluated the association of fractional exhaled nitric oxide (FeNO) and indoor air pollutants, but limited information available of the risks between schools located in suburban and urban areas. We therefore investigated the association of FeNO levels with indoor particulate matter (PM10 and PM2.5), and nitrogen dioxide (NO2) exposure in suburban and urban school areas. A comparative cross-sectional study was undertaken among secondary school students in eight schools located in the suburban and urban areas in the district of Hulu Langat, Selangor, Malaysia. A total of 470 school children (aged 14 years old) were randomly selected, their FeNO levels were measured, and allergic skin prick tests were conducted. The PM2.5, PM10, NO2, and carbon dioxide (CO2), temperature, and relative humidity were measured inside the classrooms. We found that the median of FeNO in the school children from urban areas (22.0 ppb, IQR = 32.0) were slightly higher as compared to the suburban group (19.5 ppb, IQR = 24.0). After adjustment of potential confounders, the two-level hierarchical multiple logistic regression models showed that the concentrations of PM2.5 were significantly associated with elevated of FeNO (>20 ppb) in school children from suburban (OR = 1.42, 95% CI = 1.17–1.72) and urban (OR = 1.30, 95% CI = 1.10–1.91) areas. Despite the concentrations of NO2 being below the local and international recommendation guidelines, NO2 was found to be significantly associated with the elevated FeNO levels among school children from suburban areas (OR = 1.11, 95% CI = 1.06–1.17). The findings of this study support the evidence of indoor pollutants in the school micro-environment associated with FeNO levels among school children from suburban and urban areas.