Odd ratios were calculated per IQR increase in exposure.
Model 1, single-pollutant mode. No adjustment for other pollutants and
covariates. The role of each pollutant in the mixing effect was
obtained.
In the multi-pollutant models, the VIF value of PM10,
PM2.5-10 and PM2.5 was over 5, which was
multicollinearity and not included in the model at the same time.
PM10 model (Model 2), PM2.5-10 model
(Model 3), and PM2.5 model (Model 4) were adjusted for
paternal atopy, maternal work during
pregnancy,
maternal primipara, monthly
household income, open windows often, and use an air purifier.
In the multiple logistic regression model of the effect of pollutants
during pregnancy on childhood eczema, results from the single-pollutant
model showed that O3 exposure was significant for the
risk of developing eczema at age 1 year only [1.11(1.04-1.19)] and
age 2 years only [1.23(1.06-1.42)]. After adjusting for other
pollutants and covariates in the multi-pollutant model, the results
showed that PM10 exposure was significant for
1-year old eczema only
[1.25(1.11-1.40)] and 2-years old eczema only [1.51(1.16-1.95)].
Dividing PM10 into PM2.5 and
PM2.5-10, PM2.5-10 remained positively
associated with the risk of 1-year old eczema only [1.32(1.20-1.45)]
and 2-year-old eczema only [1.24(1.00-1.54)], while
PM2.5 had no significant effect (Table 5).
In the multivariate logistic regression model in the first year of
life(Table 5), the results of the single-pollutant model showed that
PM10[1.08(1.02-1.15)], CO[1.07(1.00-1.14)], and
SO2 [1.07(1.00-1.14)]exposure were all positively
associated with only eczema at
age 1, and after dividing PM10 into
PM2.5 and PM2.5-10, both
PM2.5[1.08(1.01-1.15)]and
PM2.5-10[1.07(1.00-1.14)] were still positively
associated with only eczema at age 1, and in the multi-pollutant model,
CO [1.08(1.00-1.18)]was still positively associated with only eczema
at age 1. O3 concentration was positively associated
with only eczema at age 2, in both the single-pollutant model
[1.26(1.09-1.46)] and the multi-pollutant model
[1.24(1.03-1.50)] with statistical significance.
Table 5 OR and 95% CI for the effect of air pollutant
exposure during pregnancy on childhood
eczema in the multiple logistic
regression model.