Table 1.

Characteristics of the 15 included studies on the association between air pollution and childhood obesity.

Study ID	Author (Year)	Country	Study Design	Study Period	Sample Size (Boy %)	Age	Quality a
1	Zheng et al. (2021)	China	Cross-sectional	2019	36,456 (52.1)	9–17	13
2	Zhang et al. (2021a)	China	Cross-sectional	2013–2014	44,718 (50.5)	7–18	13
3	Zhang et al. (2021b)	China	Cross-sectional	2013–2014	9897 (50.3)	10–18	13
4	Tamayo et al. (2021)	Mexico	Cross-sectional	2006 and 2012	4306 (51.5)	2–18	11
5	Bont et al. (2021)	Spain	Cohort	2006–2018	416,955 (51.4)	2–15	12
6	Vrijheid et al. (2020)	UK	Cross-sectional	2013–2016	1301 (54.7)	6–11	11
7	Guo et al. (2020)	China	Cross-sectional	2013–2014	40,953 (48.3)	6–17	13
8	Bont et al. (2020)	Spain	Cohort	2011–2016	79,992 (51.0)	0–5	13
9	Chen et al. (2020)	China	Cohort	2012–2014	5752 (52.5)	0–2	12
10	Bont et al. (2019)	Spain	Cross-sectional	2012	2660 (51.1)	7–10	13
11	Bloemsma et al. (2019)	Netherlands	Cohort	1996–2014	3680 (51.9)	3–17	12
12	Kim et al. (2018)	US	Cohort	2002–2003	2318 (50.6)	6.5 ± 0.7	13
13	Fioravanti et al. (2018)	Italy	Cohort	2003–2004	719 (50.6)	4–8	12
14	McConnell et al. (2015)	US	Cohort	2003–2014	3318 (49.6)	10.1 ± 0.59	13
15	Dong et al. (2014)	China	Cross-sectional	2009	30,056 (50.4)	2–14	11

Abbreviations: US, United States of America; UK, United Kingdom of Great Britain and Northern Ireland. ^a National Institutes of Health’s Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies (NIH-QAT)