Table 3.

Missing data days and summary statistics of maximum daily pollutant levels in study period.

Variable (unit)		Mean	Standard Deviation	Minimum/24 hr	Maximum/24 hr	AAQC†	Number of Missing Days
SO2 (ppb)	London	3.35	2.96	0	28.63		12
	Windsor	7.36	5.06	0	37.50	100/24 hr	8
	Sarnia	9.72	12.72	0	110.17		4
NO2 (ppb)	London	18.10	7.86	0	53		54a
	Windsor	23.50	7.59	6	50	100/24 hr	11
	Sarnia	16.85	8.13	0	52		100c
O3 (ppb)	London	23.61	12.50	0	77		7
	Windsor	20.62	12.58	0	82	80/hr	6
	Sarnia	25.35	11.86	0	76		54d
CO (ppm)	London	0.16	0.30	0	3		9
	Windsor	0.60	0.44	0	3	3/hr	5
	Sarnia	0.27	0.29	0	1.4		87b

^†Ambient Air Quality Criteria (Ontario Ministry of the Environment, 2000).

a Seven or more missing days in a row: 2000 – Jan. 7–31; Feb. 1–10

b Seven or more missing days in a row: 1998 – Dec 2–31; 1999 – Jan 1–31

c Seven or more missing days in a row: 1997 – Oct. 8–16; 1998 – Sept. 24–30; Oct. 1–31; Nov. 1–10

d Seven or more missing days in a row: 2000 – Nov. 8–16

e Seven or more missing days in a row: 1997 – Jan. 17–23