Table 3.

Average levels of the 1-h and 24-h ambient pollutants and meteorological parameters prior to the starting time of the clinical visits.

Time window	Variable	Unit	$n$a	Mean (SD)	Range	IQR
1 h	${\mathrm{PM}}_{2.5}$	${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$	503	72.8 (77.1)	0.7–350.6	87.1
	BC	${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$	503	6.1 (3.6)	0.5–15.7	6.3
	UFPs	${10}^3{/\mathrm{cm}}^3$	430	15.9 (6.7)	2.2–37.8	9.4
	Acc	${10}^3{/\mathrm{cm}}^3$	430	4.4 (3.2)	0.1–14.5	4.9
24 h	${\mathrm{PM}}_{2.5}$	${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$	503	74.7 (67.3)	1.0–325.4	63.4
	BC	${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$	503	5.3 (3.1)	0.5–12.7	4.8
	UFPs	${10}^3/{\mathrm{cm}}^3$	430	15.5 (4.5)	2.9–27.5	6.0
	Acc	${10}^3/{\mathrm{cm}}^3$	430	4.5 (3.0)	0.1–13.1	4.5
	Temperature	°C	547	13.6 (10.0)	−3.9–33.7	17.8
	Relative humidity	%	547	47.8 (19.4)	11.9–99.6	33.7

Note: Acc, accumulated-mode particles; BC, black carbon; IQR, interquartile range; ${\mathrm{PM}}_{2.5}$, particulate matter with an aerodynamic diameter of $\le 2.5\mathrm{\mu }\mathrm{m}$; SD, standard deviation; UFPs, ultrafine particles.

^an denotes the number of visits with valid matched pollution concentration out of a total number of 547 person-visits.