Association Between PM2.5 Exposure in Child Care Centers and Wheeze Among Young Children in Singapore

Abstract

ISEE-440 Objective: Numerous epidemiologic studies have reported adverse effects of air PM2.5 on children's health. The objective of this study was to determine the associations between current wheeze symptom among children attending child care centers (CCCs) in Singapore and exposures to PM2.5. Material and Methods: From a large survey using the International Study on Asthma and Allergies in Childhood (ISAAC) questionnaire on 4759 children attending 104 CCCs, 15 high- and 15 low-current wheeze prevalence CCCs were selected. A total of 1551 children participated in this study. PM2.5 exposure measurements were performed indoors as well as outdoors of the CCCs. The concentrations were computed into quartiles. Prevalence ratios (PR) and 95% confidence interval (95% CI) were evaluated using Cox proportional hazard regression assuming a constant risk period controlled for the influence of confounders such as age, gender, race, familial atopy, socioeconomic status, preterm births, breast-feeding, respiratory infections, ETS, home dampness, and CCC status. Results: We found higher indoor concentrations of PM2.5 in high-prevalence CCCs than in low-prevalence CCCs (mean: 79.3 vs. 77.3 mg/m3). We found that current wheeze was associated with outdoor PM2.5 levels, as well as indoor PM2.5 levels. Comparing the categories of fourth, third, and second quartiles of indoor PM2.5, respectively, with first quartile, the adjusted PRs (95% CIs) for wheeze were 1.52 (1.00–2.31), 1.28 (0.79–2.06), and 1.13 (0.70–1.84). The corresponding adjusted PRs (95% CIs) for outdoor PM2.5 were 1.57 (1.03–2.39), 1.21 (0.80–1.84), and 1.15 (0.75–1.77). Conclusions: The slightly stronger association found for outdoor PM2.5 with wheeze symptoms suggests outdoor source of causal agent and reduction of toxicity as it is transported indoors. Given that fine particulate matter exposures of children have been considered a health risk from ambient data, the results from this study of Singapore children revealed that indoor exposures within CCC needs to be equally addressed. Therefore, CCCs should consider mitigation strategies to reduce indoor PM2.5 exposures of outdoor origin via ventilation and/or filtration.