Table 4 Correlations between modelled outdoor air pollutant concentrations by postcode sector

	Survey year
	1995	1996	1997	2001
Number of postcode sectors	715	737	641	751
Correlation* between
PM₁₀ and NO₂	0.93	0.92	0.90	0.90
PM₁₀ and O₃	−0.20	−0.35	−0.28	−0.47
PM₁₀ and SO₂	0.34	0.17	0.13	0.17
NO₂ and O₃	−0.20	−0.40	−0.39	−0.40
SO₂ and O₃	−0.29	−0.36	−0.30	−0.16
NO₂ and SO₂	0.31	0.31	0.29	0.18

*Pearson correlation coefficient.
PM₁₀, particulate matter <10 μm in diameter.