Table 1:

Summary of six articles included in the systematic review.

Study citation information and setting					Exposure			Outcome
ID	Authors(year)	Location	Study design, Time-span	Study Size	Population (years old)	Mean/median concentration	Unit of increment (μg/m3)	Exposure type	Health outcome	Outcome level	Effect (95% CI)	Controlled variables
1	Wang et al. (2021b)	Hefei, China	Time series, 2016–2018	15683	0-17	31.00	10.00	Short-term, lag0	Pneumonia	Hospital admission, ICD-10	6.82(3.85–9.88) *	Yes
2	Zhang et al. (2021)	Wuhan, China	Cross-sectional, 2014–2018	5788	3-5	37.40	10.00	Long-term	Asthma	Incidence	1.54(0.82–2.90) **	Yes
3	Zhang et al. (2020)	Shenzhen, China	Case-crossover, 2015–2016	6078	All	19.00	10.00	Short-term, lag0-2	TRD	Hospital admission, ICD-10	1.09(1.04–1.14) ***	Yes
				147	All	19.00	10.00	Short-term, lag0-2	Asthma	Hospital admission, ICD-10	1.12(0.85–1.47) ***	Yes
				1661	All	19.00	10.00	Short-term, lag0-2	Pneumonia	Hospital admission, ICD-10	1.12(1.02–1.22) ***	Yes
4	Yu et al. (2020)	Liaoning, China	Cross-sectional, 2012–2013	59754	2-17	44.90	11.40	Long-term, 2009-2012	Current asthma	Prevalence	1.55(1.38–1.75) ***	Yes
5	Luong et al. (2016)	Hanoi, Vietnam	Case-crossover, 2010–2011	8934	0-5	54.00	42.00	Short-term, lag0	TRD	Hospital admission, ICD-10	1.03(1.01–1.04) ***	Yes
6	Michaud et al. (2004)	Hawaii, America	Time series, 1997–2001	4339	NA	1.97	10.00	Short-term, lag0	Asthma	Emergency department visit, ICD-9	1.03(0.90–1.42) ****	Yes

^*PC; ^**:HR; ^***OR; ^****Effect; TRD total respiratory diseases, PCpercentage change, OR odds ratio, HR hazards ratio.