Household indoor air quality and its associations with childhood asthma in Shanghai, China: On-site inspected methods and preliminary results.

Few studies were conducted for associations of home environment with childhood health by on-site inspection in China. During 2013-2014, we conducted a case-control study with home inspection among 454 children (186 asthma children and 268 non-asthma children) in Shanghai, China. In this paper, we detailedly described the inspected methods and analyzed the preliminarily collected data. Except in winter, most residences meet the national standard for indoor temperature and relative humidity. Most living rooms had ≤1000ppm CO2, whereas over half of the child's bedrooms had slightly >1000ppm CO2 during night. Most residences had notably lower than 2500cfu/m3 airborne culturable fungi and ≤100μg/m3 formaldehyde. More than 70% of the child's bedrooms had ≤75μg/m3 PM2.5 and ≤150μg/m3 PM10. Indoor and outdoor concentrations of particulate matters had strong linear correlations (r=0.891-0.922; p-value <0.001). Most differences between cases and controls were not significant with respect to CO2, culturable fungi, formaldehyde, and particulate matters. Before and after adjusted for potential confounders, indoor averaged concentration of CO2 and particulate matters generally had negative associations with childhood history of doctor-diagnosed asthma in spring, summer, and autumn. Only in winter, indoor CO2 concentration was significantly associated with the increased odds of childhood asthma. Our results indicated that air quality among most residences in Shanghai could meet the national standard for indoor air quality in warm seasons; but household air quality and ventilation status in winter should be greatly improved. We suspected that those "unexpected" negative associations could exist due to changes in lifestyle behaviors regarding indoor air quality after the child being diagnosed asthma by a doctor.