Table 1.

Case-crossover study. Mean concentrations (mean and Area Under the Curve) of air pollutants in the 60 days before low-disease activity visit and flare visit (DAS28-CRP difference >1.2)

Pollutant		Control period (low disease activity, n=440)	Hazard period (flare, n=440)	p value
CO μg/m³	Mean	0.38	0.42	0.001
CO μg/m³	AUC	22.00	24.53	0.001
NO μg/m³	Mean	19.23	24.11	0.002
NO μg/m³	AUC	1,120.53	1,403.88	0.002
NO₂ μg/m³	Mean	30.91	32.44	0.042
NO₂ μg/m³	AUC	1,800.96	1,892.05	0.040
NO_x μg/m³	Mean	60.34	69.35	0.004
NO_x μg/m³	AUC	3,515.77	4,041.06	0.004
PM10 μg/m³	Mean	31.21	33.65	0.011
PM10 μg/m³	AUC	1,789.22	1,942.52	0.005
O₃ μg/m³	Mean	31.08	33.79	0.002
O₃ μg/m³	AUC	1,776.37	1,934.35	0.001
PM2.5 μg/m³	Mean	23.08	24.74	0.018
PM2.5 μg/m³	AUC	1,272.61	1,403.60	<0.001