Table 6 Mean odds ratios (per 10 μg/m³ increase in NO₂, from single‐pollutant model), categorised by potential effect modifiers for selected outcomes.

	Pet allergy	Hay fever	Itchy rash	Asthma	Bronchitis
Asthmatic status (parent)
Asthmatic	1.26 (0.94–1.69)	1.11 (0.98–1.25)	1.00 (0.91–1.10)	1.05 (0.86–1.28)	1.07 (0.73–1.55)
Non‐asthmatic	1.14 (0.93–1.39)	1.04 (0.92–1.17)	1.06 (0.96–1.17)	1.02 (0.95–1.08)	0.97 (0.89–1.07)
Sex
Male	1.15 (0.96–1.37)	1.01 (0.89–1.15)	1.10 (0.98–1.24)	1.02 (0.91–1.15)	0.99 (0.90–1.08)
Female	1.10 (0.97–1.24)	1.09 (1.00–1.18)	0.99 (0.94–1.04)*	1.03 (0.96–1.11)	0.99 (0.86–1.13)
Age (years)
6–8	1.07 (0.96–1.20)	1.00 (0.93–1.08)	1.03 (0.99–1.08)	0.97 (0.91–1.04)	0.98 (0.84–1.15)
9–12	1.15 (0.96–1.37)	1.08 (1.01–1.16)	1.04 (0.94–1.14)	1.10 (0.96–1.25)	1.00 (0.91–1.10)

“H” indicates heterogeneity between study‐specific results (p<0.10).

*Borderline significant effect modification (p<0.10).