2.3 Exposure assessment of the air pollutants
The ambient air pollutant data were obtained from dynamic monitoring data of air pollutants collected at 17 ambient air quality monitoring stations in Jinan. Daily 24-hour average concentrations of SO2, NO2, CO, PM10, PM2.5, and daily maximum 8-hour average concentrations of O3 were obtained for the birth cohort population between the date of the last menstrual period of the earliest pregnant mother and the date of birth of the latest child who had reached the age of 2 years. Then obtained the PM2.5-10 concentration by subtracting the PM2.5 concentration from the PM10 concentration. The residence address of the mother during pregnancy and after the birth of the child, the date of the mother’s last menstrual period for the current pregnancy and the date of birth of the child were collected through questionnaires at the baseline and follow-up surveys of the cohort study, and the pollutant concentrations measured at 17 monitoring stations were weighted according to the spatial distance between the home address and the concentration at the monitoring station using the Inverse Distance Weighting (IDW) model to obtain the individual pollutant concentrations for each study subject(Rishikeshan, Katiyar, Mahesh, & Ieee, 2014).
2.4 Covariate
Child information Gender, birth weight, breastfeeding, birth mode, use of masks, and preterm birth.
Parental information Parental atopy, maternal age at delivery, work during pregnancy, maternal primipara.
Family information House decoration, home dampness, use of carpet, pets, monthly household income, open windows often, air purifier use.
Parental atopy was defined as either parent having had an allergic disease, including eczema, allergic rhinitis, food and drug allergy, or asthma. Working during pregnancy was defined as the act of the mother continuing to work in the workplace during pregnancy. Home dampness was defined as having at least one of the following dampness-related exposures in the dwelling environment: visible mold stains, visible damp stains, damp clothing/bedding, condensation on windows, or moldy odors. Open windows often was defined as three or more window openings in a week by the child’s cohabitants.