Table 2

Characteristics of studies investigating the association of long-term exposure to outdoor particulate air pollution and FEV₁ in healthy adults (n=10)

Authors/date	Region/country	Population (n)	Age	Time period	Pollutants (µg/m³) and measurement method/resolution	Outcome (change or absolute level per 10 µg/m³ increase in pollutant when applicable)	Statistical model
Change in FEV₁
Rice et al 36	USA, multiple regions	Framingham cohort and Third Generation cohort: non-smoking adults (2222).	Mean age: 50.4 years.	2002–2005 and 2008–2011	Annual mean PM_2.5 (mean 10.8) Satellite based (10 km by 10 km) and land use regression to 50 m by 50 m resolution	−10.5 mL (95% CI −20.5 to 1.0).	Linear regression (yes).
Eckel et al 28	USA, multiple regions	Adults aged >65 years, part of Cardiovascular Health Study Cohort (3382).	Mean age: 73.6 years.	1989–1997	5 month mean particulate matter with aerodynamic diameter less than 10 µm (PM₁₀) (mean 31.5 µg/m³) Fixed site monitor interpolation	Men: −6.7 mL (95% CI −26.9 to 13.4). Women: −20.2 mL (95% CI −32.6 to −7.7).	General additive models (yes).
Agarwal et al 24	Punjab, India	Adults aged 13–59 years, non-smokers and no history respiratory disease (51).	Mean age: 30 years.	2007–2008	2 month mean PM₁₀ and PM_2.5 (mean 49 and 89) Fixed site 1 km by 1 km resolution	PM₁₀: −22.4 mL (95% CI −42.8 to 2.0). PM_2.5: −44.0 mL (95% CI −86.1 to 0.1).	Linear regression (yes).
Götschi et al 31	10 European countries	European Community Respiratory Health Survey (ECRHS) cohort; non-asthmatic adults aged aged 20–44 years (3772).	Mean age: 40 years.	1991–1993 and 2000–2002	Annual mean PM_2.5 (mean 16.8). Fixed site interpolation.	Women: 1.1 mL (95% CI −0.22 to 2.42). Men: 0.23 mL (95% CI −0.22 to 0.68).	Regression model (no).
Downs et al 27	Switzerland	Swiss Cohort Study on Air Pollution and Lung and Heart Diseases in Adults (SAPALDIA) Cohort; non-smokers aged 18–60 years (2213).	Mean age: 41.5 years.	1991–2002	Annual mean PM₁₀ (mean 21.6). Fixed site 200 m by 200 m resolution.	−4.2 mL (95% CI −8.50 to 0.30).	Mixed-model regression analysis (yes).
Sekine et al 42	Tokyo, Japan	Non-smoking women with no history respiratory disease aged 30–59 years (406).	Mean age: 45 years.	1987–1994	8 year mean PM₁₀ (mean 44.8). Fixed site 20 m near road and homes 20 m near road.	−5.01 mL (95% CI −7.89 to −2.13).	General linear model (yes).
Absolute FEV₁
Rice et al 36	USA, multiple regions	Framingham cohort and Third Generation cohort: non-smoking adults (2222).	Mean age: 50.4 years.	2002–2005 and 2008–2011	Annual mean PM_2.5 (mean 10.8). Satellite based (10 km by 10 km) and land use regression to 50 m by 50 m resolution.	−67.5 mL (95% CI 133.0 to −15.0)	Linear mixed-effects model (yes).
Forbes et al 29	England, multiple regions	Caucasian >16 (40 329).	92.2% <75.	1995–2001	Annual mean PM₁₀ (mean 18.8) Fixed site monitor 1 km by 1 km resolution	PM₁₀ among healthy: −81 mL (95% CI −118 to −44).	Fixed-effects regression model (yes).
Götschi et al 31	10 European countries	ECRHS cohort; non-asthmatic adults aged 20–44 years (3772).	Mean age: 40 years.	1991–1993 and 2000–2002	Annual mean PM_2.5 (mean 16.8) Fixed site interpolation	Women: 95.6 mL (95% CI −31.3 to 222.5). Men: 470.5 mL (95% CI 153.8 to 787.2).	Regression model (no).
Schikowski et al 41	Germany, multiple regions	Study on the influence of Air pollution on Lung function, Inflammation and Aging (SALIA) cohort: women with no history of asthma (4754).	Mean age: 54.5 years.	1985–1994	Five year mean PM₁₀ (mean 48). Fixed site within 8 km of residence.	−185.6 mL (95% CI −280.5 to −90.7).	Logistic regression models (yes).
Abbey et al 22	California, USA	Non-smoking, non-morbidly obese adults with no history of congestive heart failure (CHF) (1391).	Mean age: 65.6 years.	1977–1993	20 year mean PM₁₀ (mean 53). Fixed site monitor interpolation.	Men: −0.67 mL (95% CI −354.09 to 352.75). Women: +3.15 mL (95% CI −19.63 to 25.93).	Sex-specific multiple linear regressions (yes).
Ackermann-Liebrich et al 23	Switzerland, multiple regions	SAPALDIA cohort: healthy never-smokers aged 18–60 years (9651).	46.4% <40	1991	Annual mean PM₁₀ (mean 21.2). Fixed site 200 m by 200 m resolution.	−56.00 mL (95% CI −79.65 to −32.35).	Regression analysis (yes).

FEV1, forced expiratory volume in 1 s.