Table 2

Correlations between participant air pollution estimates and potential confounders

	BS 1971	SO₂ 1971	BS 1981	SO₂ 1981	BS 1991	SO₂ 1991	PM₁₀ 2001	Age	Population density	RR lung cancer
BS 1971 n=367 658	1.000
SO₂ 1971 n=367 658	0.730	1.000
BS 1981 n=305 471	0.696	0.531	1.000
SO₂ 1981 n=305 471	0.519	0.720	0.762	1.000
BS 1991 n=259 649	0.651	0.405	0.769	0.538	1.000
SO₂ 1991 n=259 649	0.645	0.452	0.750	0.600	0.866	1.000
PM₁₀ 2001 n=221 148	0.195	0.411	0.200	0.413	0.077	0.190	1.000
Age n=367 658	−0.002	0.012	−0.020	−0.005	−0.035	−0.034	−0.014	1.000
Population density n=367 658	0.441	0.689	0.252	0.438	0.044	0.107	0.380	0.031	1.000
RR lung cancer n=221 148	0.059	−0.162	0.010	−0.202	0.007	0.047	−0.191	0.004	−0.150	1.000

Population Density—population density 1 km grid. Source: Office for National Statistics Longitudinal Study (authors’ own work).
BS, black smoke.