Table 7

Analysis of subgroups based on atopic status (Birmingham n=27, Sandwell n=23) and parental history of recent wheezing (Birmingham n=23, Sandwell n=16) subgroups. Results are only shown for selected pollutants and morning ΔPEF (l/min)

		Subgroup with atopy or history of recent wheezing		Subgroup without atopy or history of wheezing
Pollutant	Lag (days)	Effect size†	95% CI	Effect size†	95% CI	Difference between subgroups
*Effect estimate significantly different from zero (p<0.05).
†Effect size=ΔPEF per μg/m³ increase in pollutant.
Subgroups based on atopic status:
PM₁₀	0	−0.088	−0.403 to 0.226	0.086	−0.285 to 0.456
	1	−0.105	−0.407 to 0.198	0.008	−0.363 to 0.379
	2	0.118	−0.220 to 0.456	−0.014	−0.439 to 0.412
	3	−0.034	−0.363 to 0.295	−0.005	−0.399 to 0.388

PM_2.5	0	−0.072	−0.527 to 0.383	0.126	−0.413 to 0.666
	1	−0.271	−0.701 to 0.159	0.193	−0.340 to 0.728
	2	0.127	−0.354 to 0.608	−0.170	−0.788 to 0.447
	3	0.055	−0.391 to 0.501	−0.314	−0.846 to 0.216

HNO₃	0	3.506	−4.273 to 11.285	−5.964	−15.195 to 3.266	p<0.05
	1	−0.445	−8.083 to 7.192	−3.866	−12.741 to 5.010
	2	−7.616*	−14.989 to −0.242	2.588	−6.644 to 11.819	p<0.05
	3	3.240	−4.568 to 11.048	−5.384	−14.498 to 3.730

SO₄²⁻	0	0.200	−0.755 to 1.156	−0.613	−1.714 to 0.488
	1	−0.219	−1.318 to 0.881	−0.174	−1.423 to 1.075
	2	−0.431	−1.526 to 0.664	0.006	−1.243 to 1.253
	3	1.200*	0.095 to2.305	−1.080	−2.308 to 0.148	p<0.05

NO₃⁻	0	−0.036	−0.627 to 0.555	−0.434	−1.116 to 0.248
	1	0.142	−0.573 to 0.857	−0.201	−1.002 to 0.600
	2	0.000	−0.760 to 0.759	0.154	−0.703 to 1.010
	3	0.689	−0.061 to 1.439	−0.605	−1.422 to 0.210	p<0.05

Subgroups based on parental history of recent wheezing:
PM₁₀	0	0.072	−0.069 to 0.212	0.019	−0.235 to 0.273
	1	0.094	−0.045 to 0.233	−0.065	−0.324 to 0.193
	2	0.013	−0.139 to 0.166	0.031	−0.267 to 0.330
	3	−0.044	−0.189 to 0.102	−0.005	−0.276 to 0.265

PM_2.5	0	0.187	−0.008 to 0.382	0.026	−0.341 to 0.395
	1	−0.006	−0.207 to 0.195	0.068	−0.307 to 0.444
	2	−0.011	−0.226 to 0.204	−0.099	−0.535 to 0.335
	3	−0.037	−0.228 to 0.154	−0.252	−0.615 to 0.110

HNO₃	0	1.005	−2.115 to 4.124	−4.324	−10.556 to 1.907
	1	−2.266	−5.135 to 0.603	−2.982	−8.869 to 2.904
	2	−1.835	−4.775 to 1.105	−0.157	−6.499 to 6.183
	3	−0.442	−3.366 to 2.481	−3.445	−9.496 to 2.607

SO₄²⁻	0	0.457*	0.003 to 0.910	−0.622	−1.379 to 0.136	p<0.05
	1	0.078	−0.503 to 0.660	−0.272	−1.147 to 0.602
	2	−0.102	−0.656 to 0.452	−0.138	−1.005 to 0.728
	3	0.002	−0.609 to 0.613	−0.496	−1.359 to 0.367

NO₃⁻	0	0.228	−0.054 to 0.511	−0.482*	−0.952 to −0.012	p<0.05
	1	0.476*	0.060 to 0.892	−0.276	−0.846 to 0.294	p<0.05
	2	0.196	−0.202 to 0.594	0.078	−0.520 to 0.675
	3	0.083	−0.321 to 0.487	−0.298	−0.864 to 0.268