Table 2.

Distribution of PM_2.5 as the difference between the index^a and referent^b measures for each lag.

PM2.5 μg/m3	N	Mean	Standard Deviation	Median	Interquartile Range
Bronchiolitis
Lag 0	16359	0.17	7.34	0.13	8.20
Lag 1	16357	0.06	7.28	0.48	8.17
Lag 4	16281	0.11	7.37	0.10	8.11
Lag 7	16295	0.01	7.21	−0.02	8.10
Otitis Media
Lag 0	37040	0.01	7.64	0.03	8.11
Lag 1	37114	−0.08	7.50	−0.06	8.12
Lag 4	37090	0.06	7.61	0.08	8.23
Lag 7	37117	0.03	7.63	0.03	8.03

^aIndex days are days lagged in reference to date of clinical encounter of a case.

^bReferent day for each case is randomly assigned as one week before or after index day.