Table 1.

Descriptive Statistics of Biomarkers in Urine Samples in Beijing (BJ) and Los Angeles Before (LA₁) and After the Trip (LA₂)

biomarker	median (IQRa)			p valueb			Beijing/LA concentration ratio (95%CI;p value)c
	in LA1(n = 30)	in BJ(n = 47)	in LA2(n = 27)	LA1 vs BJ	LA2 vs BJ	LA1 vs LA2
exposure biomarker (ug/g creatinine)
1-hydroxynaphthalene	0.91 (0.35, 1.45)	1.91 (1.01, 2.62)	0.41 (0.29, 1.05)	< 0.001	< 0.001	0.08	2.6 (1.7–4.0; < 0.001)
2-hydroxynaphthalene	2.58 (1.13, 4.57)	2.74 (1.77, 5.00)	2.43 (1.36, 3.87)	0.34	0.28	0.95	1.1 (0.79–1.5; 0.67)
Σhydroxynaphthalenes	3.08 (1.85, 5.82)	5.01 (2.95, 7.94)	2.76 (1.87, 4.41)	< 0.05	< 0.05	0.57	1.3 (0.97–1.8; 0.08)
2-hydroxybiphenyl	0.45 (0.25, 1.16)	0.45 (0.24, 1.10)	0.66 (0.42, 1.46)	0.87	0.19	0.20	1.1 (0.66–1.7; 0.82)
4-hydroxybiphenyl	0.30 (0.17, 0.45)	1.29 (0.85, 1.98)	0.30 (0.18, 0.43)	< 0.001	< 0.001	0.87	3.7 (2.7–5.0; < 0.001)
4,4′-dihydroxybiphenyl	0.29 (0.18, 0.52)	0.91 (0.76, 1.29)	0.29 (0.18, 0.45)	< 0.001	< 0.001	0.89	2.7 (2.0–3.7; < 0.001)
Σhydroxybiphenyls	1.39 (0.72, 2.22)	2.93 (1.84, 4.79)	1.54 (0.94, 2.77)	< 0.001	< 0.01	0.33	2.3 (1.6–3.2; < 0.001)
2-hydroxydibenzofuran	0.25 (0.14, 0.47)	1.80 (1.24, 2.07)	0.25 (0.20, 0.34)	< 0.001	< 0.001	0.60	6.1 (4.6–7.9; < 0.001)
2-hydroxyfluorene	0.20 (0.10, 0.33)	1.21 (0.80, 1.64)	0.19 (0.12, 0.25)	< 0.001	< 0.001	0.99	5.7 (4.4–7.6; < 0.001)
3-hydroxyfluorene	0.08 (0.04, 0.14)	0.41 (0.31, 0.55)	0.07 (0.04, 0.11)	< 0.001	< 0.001	0.59	5.5 (4.0–7.5; < 0.001)
Σhydroxyfluorenes	0.29 (0.13, 0.49)	1.58 (1.17, 2.31)	0.26 (0.17, 0.34)	< 0.001	< 0.001	0.91	5.6 (4.3–7.4; < 0.001)
1-hydroxyphenanthrene	0.12 (0.06, 0.21)	0.41 (0.30, 0.73)	0.08 (0.06, 0.17)	< 0.001	< 0.001	0.29	3.9 (2.9–5.2; < 0.001)
2-hydroxyphenanthrene	0.08 (0.04, 0.13)	0.26 (0.15, 0.36)	0.06 (0.04, 0.12)	< 0.001	< 0.001	0.53	3.5 (2.7–4.6; < 0.001)
4-hydroxyphenanthrene	0.04 (0.02, 0.07)	0.12 (0.07, 0.20)	0.04 (0.02, 0.10)	< 0.001	< 0.001	0.87	2.7 (1.9–3.9; < 0.001)
Σhydroxyphenanthrenes	0.25 (0.15, 0.43)	0.92 (0.52, 1.26)	0.20 (0.13, 0.36)	< 0.001	< 0.001	0.48	3.5 (2.6–4.6; < 0.001)
1-hydroxypyrene	0.09 (0.05, 0.16)	0.32 (0.18, 0.46)	0.07 (0.05, 0.13)	< 0.001	< 0.001	0.99	3.3 (2.4–4.6; < 0.001)
Σ8hydroxylated PAHsd	3.76 (2.16, 7.06)	8.85 (4.99, 12.1)	3.27 (2.37, 5.54)	< 0.01	< 0.001	0.62	1.8 (1.3–2.4; < 0.001)
Σ12hydroxylated PAHse	5.77 (3.63, 10.6)	14.1 (7.68, 20.5)	5.78 (3.70, 10.5)	< 0.001	< 0.001	0.85	2.0 (1.5–2.7; < 0.001)
metabolite ratio
1/2-hydroxynaphthalene	0.29 (0.13, 0.55)	0.53 (0.34, 0.96)	0.15 (0.11, 0.34)	< 0.01	< 0.001	0.14	2.5 (1.7–3.5; < 0.001)
1 + 2/4-hydroxyphenanthrene	3.99 (2.88, 7.48)	5.08 (4.15, 8.15)	4.00 (2.91, 5.83)	0.07	< 0.01	0.46	1.4 (1.1–1.7; < 0.01)
effect biomarker (ug/g creatinine)
malondialdehyde	53.7(36.6, 72.5)	48.4 (39.4, 68.3)	49.6 (38.4, 90.8)	0.75	0.40	0.78	0.93 (0.77–1.2; 0.46)

^aIQR: interquartile range.

^bMann–Whitney test.

^cRatio =10^β, where β is the estimated slope for city in multivariate linear regression models with the enter approach and OH-PAHs is log-transformed. Ratios are adjusted by age, gender, and BMI.

^dSum of hydroxynaphthalenes, hydroxyfluorenes, hydroxyphenanthrenes, and 1-hydroxypyrene.

^eSum of hydroxynaphthalenes, hydroxybiphenyls, 2-hydroxydibenzofuran, hydroxyfluorenes, hydroxyphenanthrenes, and 1-hydroxypyrene.