Table 4.

Chi-square values and risk ratios^* for associations between various lags of each pollutant metric and respiratory emergency department visits

POLLUTANT	Metric	χ2 lag 0	χ2 lag1	χ2 lag2	χ2 lag3
CO	1-hr max	36.8 (1.018)	30.6 (1.014)	27.3 (1.013)	26.8 (1.013)
	24-hr ave	44.6 (1.019)	39.4 (1.015)	29.4 (1.012)	21.8 (1.011)
	commute	15.6 (1.011)	10.6 (1.007)	10.1 (1.007)	4.1 (1.004)
	day-time	4.6 (1.007)	2.0 (1.004)	4.2 (1.005)	0.9 (1.002)
	night-time	60.6 (1.020)	46.8 (1.011)	23.9 (1.008)	24.7 (1.008)
NO2	1-hr max	48.7 (1.020)	22.1 (1.011)	45.9 (1.014)	50.9 (1.015)
	24-hr ave	50.4 (1.021)	21.8 (1.012)	47.2 (1.016)	49.6 (1.017)
	commute	34.3 (1.017)	11.1 (1.008)	32.3 (1.013)	23.9 (1.012)
	day-time	7.4 (1.009)	1.2 (1.003)	9.3 (1.008)	10.2 (1.008)
	night-time	97.1 (1.027)	42.4 (1.016)	59.1 (1.018)	48.1 (1.016)
O3	8-hr max	28.7 (1.027)	23.9 (1.020)	33.2 (1.021)	40.1 (1.022)
	1-hr max	28.4 (1.026)	22.7 (1.018)	35.1 (1.020)	37.0 (1.020)
	24-hr ave	3.4 (1.009)	3.4 (1.007)	3.1 (1.007)	9.3 (1.011)
	commute	1.8 (1.007)	2.2 (1.006)	6.1 (1.009)	14.5 (1.014)
	day-time	19.5 (1.024)	18.3 (1.018)	23.7 (1.019)	28.3 (1.019)
	night-time	4.3 (0.993)	8.6 (0.991)	3.6 (0.994)	1.7 (0.996)
PM2.5	1-hr max	1.3 (0.996)	2.9 (1.004)	0.1 (0.999)	2.3 (1.004)
	24-hr ave	0.9 (0.996)	0.2 (1.004)	1.2 (1.003)	3.4 (1.006)
	commute	0.7 (0.996)	2.5 (1.005)	1.1 (1.003)	5.7 (1.007)
	day-time	2.6 (0.993)	0.8 (1.003)	0.4 (1.002)	3.8 (1.006)
	night-time	0.3 (0.998)	2.3 (1.004)	1.7 (1.004)	1.4 (1.003)

^*RR per interquartile increase in pollutant metric