Table 3. Correlations of air pollutants across 14 communities.

	NO2	CO	SO2	PM2.5	O3
NO2	1.00	0.86*	0.55*	0.37	−0.07
CO		1.00	0.16	0.09	−0.33
SO2			1.00	0.68*	0.37
PM2.5				1.00	0.73*
O3					1.00

Abbreviations: NO₂, nitrogen dioxide; PM₁₀, particles with aerodynamic diameter 10 µm or less; SO₂, sulphur dioxide; O₃, ozone; CO, carbon monoxide.

^*Correlation is significant at the 0.05 level.