Table 1

Characteristics of studies investigating the association of acute exposure to outdoor particulate air pollution and FEV₁ in healthy adults (n=13)

Authors/date	Region/country	Population (n)	Age	Time period	Pollutants (µg/m³) and measurement method/resolution	Outcome (change per 10 µg/m³ increase in pollutant when applicable)	Statistical model (adequate control for confounding)
Change in FEV₁
Stieb et al 44	Ontario, Canada	Healthy adults ages 55+ years (77).	Mean age: 64 years.	2013–2014	Daily mean PM_2.5 (mean 12.3–15.9). Fixed site 1 km by 1.5 km resolution (on site).	−9.38 mL (95% CI −18.02 to −0.74).	Linear mixed-effect regression models (yes).
Int Panis et al 43	Belgium	Healthy adults (2449).	Mean age: 37 years.	2011–2015	Daily mean PM₁₀ (mean 24.3). Fixed site 6 km away.	−15.8 mL (95% CI −21.9 to −9.6).	Random intercept model (yes).
Hao et al 32	Junan County, China	Healthy adults (42).	Mean age: 55 years.	2011–2012	Daily mean PM_2.5 (mean 146.5). Personal sampler pump.	−1.73 mL (95% CI −5.90 to 2.41).	Linear mixed-effects models (yes).
Huang et al 33	Beijing, China	Healthy non-smoking university students (40).	Mean age: 24 years.	2012	Daily mean PM_2.5 (mean 162.1). Personal sampler backpack.	−0.39 mL (95% CI −8.20 to 7.812).	Mixed linear models (yes).
Santos et al 37	São Paulo, Brazil	Street/park workers, males, non-smokers aged 18–65 years (101).	Mean age: 48.4 years.	2008–2012	Daily mean PM_2.5 (mean 36.6). Personal sampler.	−53.00 mL (95% CI −112.0 to 6.0).	Multiple linear regressions (yes).
Kesavachandran et al 34	National Capital Area, India	Non-smokers aged 18–50 years with no history of respiratory disease (757).	Mean age: 31.4 years.	Not specified	Daily mean PM_2.5 (median 238). Personal sampler.	−10.00 mL (95% CI −14.71 to −5.29).	Regression models (no).
Girardot et al 30	Tennessee, USA	Non-smoking adults (354).	Mean age: 43.2 years.	2002–2003	1 hour mean PM_2.5 (mean 15.0). Fixed monitor on site.	−1.01 mL (95% CI −22.88 to 20.85).	Multiple linear regressions (yes).
Trenga et al 39	Seattle, USA	Elderly non-smokers (33).	Median age: 76 years.	1999–2002	Daily median PM_2.5 (median 8.6). Personal monitor.	−29.00 mL (95% CI −62.50 to 4.50).	Mixed-effects random intercepts regression model (yes).
Korrick et al 35	New Hampshire, USA	Non-smoking adults (530).	Mean age: 35 years.	1991–1992	Daily mean PM_2.5 levels (mean 15). Fixed site monitor on site.	−13.90 mL (95% CI −26.00 to −1.80).	Logistic regression model (yes).
Absolute FEV₁
Borlée et al 25	The Netherlands, multiple regions	Adults from general population (10% COPD) (2308).	Mean age 54.7	2014–2015	Weekly mean PM₁₀ (median 18.9). Fixed site monitor.	PM₁₀: −12.5 mL (95% CI −36.0 to 10.5).	Mixed generalised additive model (yes).
Zhou et al 40	China, multiple regions	Lifelong non-smoking females (1694).	Mean age: 56.0 years.	2014–2015	Daily mean PM₁₀ and PM_2.5 (112.3 and 60.71). Fixed site monitor.	PM₁₀: 0.05 mL (95% CI −0.13 to 0.2). PM_2.5: 0.13 mL (95% CI −0.26 to 0.51).	Linear mixed model (yes).
Cakmak et al 26	Canada, multiple regions	Canadian Health Measures Survey (CHMS) cohort: ages 6–79 years (5011).	Mean age: 39.3.	2007–2009	Daily mean PM_2.5 (mean 6). Fixed site monitor.	−40.29 mL (95% CI −71.89 to 8.50).	Generalised linear mixed model (yes).
Steinvil et al 38	Tel Aviv, Israel	Tel Aviv Sourasky Medical Center Inflammation Survey (TAMCIS) cohort: never-smokers with no respiratory or cancer history (2380).	Mean age: 43 years.	2002–2007	Daily and weekly mean PM₁₀ (mean 61.8). Fixed site monitor.	Daily: −0.36 mL (95% CI −3.27 to 2.18).	Linear regression model (yes).

FEV1, forced expiratory volume in 1 s.