Associations between measured air pollutants and children’s health

Associations between the measured air pollutants or other characteristics of the school environment and children’s health were analysed using linear or logistic regression, Student’s t-test, or the non-parametric Mann-Whitney test. For the logistic regression analysis, we calculated the adjusted (corrected) associations (odds ratios) using age, gender, parental smoking at home, living density at home, and country as correction factors. Statistical significance was established at a probability level of 0.05 (p<0.05), although borderline significance (p<0.1) was also mentioned (p: ~).

One of the asthma-related symptoms (wheezing after exercise) was significantly associated with indoor CO2 concentrations measured in the classrooms: children in classrooms with CO2 concentrations above 2,000 ppm experienced a 99 percent increased risk of wheezing after exercise, compared to those in classrooms with lower indoor levels of CO2 (

Figure 9).

Prevalence (%) of children wheezing after exercise in classrooms with indoor concentrations of CO2 below or above 2,000 ppm

In the figure, cOR is the corrected odds ratio. Odds refers to the ratio of probability of occurrence of an event to that of non-occurrence: OR=1.0 means there is no difference. OR=1.88 means an 88 percent increase in risk. CI=95% (confidence intervals) means a 95 percent probability that the given value is within the given range.

Significant differences can be observed in the prevalence of children woken up by wheezing and of children with any doctor-diagnosed allergy between classrooms with indoor benzene concentrations above or below 5 μg/m3

Figure 10).

Prevalence of children woken by wheezing or with any doctor-diagnosed allergy in classrooms with indoor concentrations of benzene below or above 5 µg/m3

Similar differences were found with respect to the prevalence of children with a regular day/night cough between classrooms with indoor concentrations of xylenes above or below 10 μg/m3

Figure 11).

Prevalence (%) of children with regular day/night cough in classrooms with indoor concentrations of xylenes below or above 10 µg/m3

Ministero Dell'ambiente Italian Trust Fund