Table 3

Studies of long-term relationships between air pollution and mortality

Author	Population	Health variable(number of cases)	Exposure variables(resolution)	Adjustment variables	SES variables(resolution)	Method of evaluation of effect modification	Relative risks(95% confidence intervals)
BMI, body mass index; BS, black smoke; FEV₁, forced expiratory volume in 1 s; FVC, forced vital capacity; HS, high school; NO₂ nitrogen dioxide; PM_2.5, particulate matter with an aerodynamic diameter of up to 2.5 μm; SO₂, sulfur dioxide; TSP, total suspended particulates.
Krewskiet al⁴⁴	8111 subjects of the Six Cities cohort,25–74 years at enrollment,follow-up:1974–1991	Non-trauma mortality(1430)Cardio-pulmonary mortality(unknown)	PM_2.5^,Sulfates(city)	Active and passive smoking,BMI, alcohol consumption,occupational exposures to dust and fumes	Educational attainment:<HS HS>HS (individual)	Stratified analysis	All-cause mortality (PM_2.5)<HS 1.45 (1.13 to 1.85)HS 1.30 (0.98 to 1.73)>HS 0.97 (0.71 to 1.34)Cardiopulmonary mortality (PM_2.5)<HS 1.28 (0.92 to 1.77)HS 1.42 (0.98 to 2.08)>HS 1.40 (0.88 to 8.23)All-cause mortality (sulfates)<HS 1.47 (1.14 to 1.89)>HS 0.99 (0.72 to 1.36)Cardiopulmonary mortality (sulfates)<HS 1.28 (0.91 to 1.79)>HS 1.47 (0.90 to 2.24)
Krewskiet al⁴⁴	Subjects of the American Cancer Society(ACS) cohort,⩾30 years at enrollment,follow-up:1982–1989;295 223 subjects for the PM_2.5 cohort;552 138 subjects for the sulfate cohort	Non-trauma mortality(20 765)Cardio-pulmonary mortality(unknown)	PM_2.5^,Sulfates(city)	Active and passive smoking,BMI, alcohol consumption,occupational exposures to dust and fumes	Educational attainment:<HS HS>HS(individual)	Stratified analysis	All-cause mortality (PM_2.5) <HS 1.35 (1.17 to 1.56) HS 1.23 (1.07 to 1.40) >HS 1.06 (0.95 to 1.17) <HS 1.47 (1.21 to 1.78) HS 1.35 (1.11 to 1.64) >HS 1.14 (0.98 to 1.34) All-cause mortality (sulfates) <HS 1.27 (1.13 to 1.42) >HS 1.05 (0.96 to 1.14) Cardiopulmonary mortality (sulfates) <HS 1.39 (1.20 to 1.62) >HS 1.11 (0.98 to 1.25)
Filleulet al⁴⁵	14 284 Residents of 7 French cities,25–59 years at enrollment,follow-up:1974–2000,living in one of 21 defined city sub-divisions,excluding manual workers	Non-trauma mortality(2396)	BS, TSP,NO₂ (18 city subdivisions:0.5–2.3 km in diameter)	Active smoking,smoking status of partner,BMI,occupational exposures to dust, gas and fumes	Educational attainment:-primary-secondary-university(individual)	Stratified analysis	Results in graphic form No trend as a function of educational level for any of the 3 pollutants
Hoek et al⁴⁶	4492 Dutch NLCS cohort subjects,55–69 years at enrollment,follow-up:1986–1994	Non-trauma mortality(489)	BS,3-component measurement(regional background,urban background and proximity to major roads) (residence address)	Active smoking,smoking status of partner,last occupation(not codable,never paid work,blue collar,upper white collar,other), alcohol intake, BMI(Quetelet index),total fat intake,vegetable and fruit consumption	Educational attainment-primary school-basic vocational education-⩾HS (individual)	Stratified analysis	Primary school 1.62 (0.97 to 2.70),lower vocational education 1.24 (0.79 to 1.94),⩾HS 1.16 (0.64 to 2.10)Differences not statistically significant (p = 0.434 for medium vs low and p = 0.403 for high vs low
Finkelsteinet al⁴⁷	5228 residents of Hamilton-Burlington,(Canada)>40 years who had a lung function test follow-up:1992–2001	Non-trauma mortality(604)	TSP, SO₂(means for 3 years transposed to entire study period)above or below the median concentrations measured(41 μg.m⁻³for TSP and 4.6 ppb for SO₂)(residence address)	BMI, lung function(FEV₁, FVC),chronic pulmonary diseases, chronic ischaemic heart disease, diabetes mellitus	Mean household income (above or below median for the area study)(enumeration area)	Stratified analysis	Relative risks higher for the low household income category:for TSP low household income 1.14 (1.07 to 1.20)high household income 1.04 (1.01 to 1.06)for SO₂low household income 1.18 (1.11 to 1.26)high household income 1.03 (0.83 to 1.28)
Finkelsteinet al¹⁶	5228 residents of Hamilton-Burlington,(Canada)>40 years who had a lung function test follow-up:1992–2001	Cardio-vascular mortality(252)	Pollution index(sum of standardised values of SO₂ and TSP concentrations)(residence address)- Traffic proximity(major urban road <50 m or highway<150 m) (residence address)	BMI, lung function(FEV₁, FVC),chronic pulmonary diseases, chronic ischaemic heart disease, diabetes mellitus	Deprivation index(composite)DI = −0.66log(income)+0.55unemployment rate+0.51*%of residents who did not complete high school)(enumeration area)	Introduction of deprivation index as interaction term	No statistically significant interaction for pollution index or traffic proximity(data not shown by authors)