Internal exposure levels of polycyclic aromatic hydrocarbons in children and adolescents: a systematic review and meta-analysis

Table 5 Urinary concentration of four PAH metabolites between living with higher environmental exposure group and living with lower environmental exposure group

Metabolites	No. of studies	Model	SMD (95%CI)	p	Heterogeneity
Metabolites	No. of studies	Model	SMD (95%CI)	p	χ²	p	I²
1-OHNap (Additional file 1: Figure S7)	2	Fixed effects	0.35 [− 1.28,1.99]	0.67	1.59	0.21	37%
2-OHPhe (Additional file 1: Figure S8)	2	Random effects	0.02 [− 0.11, 0.16]	0.75	5.30	0.02	81%
3-OHPhe (Additional file 1: Figure S9)	3	Random effects	− 0.16 [− 0.55,0.23]	0.42	6.46	0.04	69%
3-OHPhe (Additional file 1: Figure S9)	2^a	Fixed effects	− 0.34 [− 0.57, − 0.12]	0.003	0.29	0.59	0%
4-OHPhe (Additional file 1: Figure S11)	3	Fixed effects	− 0.48 [− 0.69, − 0.28]	< 0.01	1.45	0.48	0%

^aSensitivity analysis of meta-analysis on differences of levels of 3-OHPhe in children and adolescents with different living conditions (Additional file 1: Figure S10)

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