Table 2. Relationship between air pollutant exposure and pubertal development

Author	Air pollutant exposure		Outcomes	Effect measure	Result with 95% CI	Adjusted variables	Average concentration of main air pollutants
Yang et al. [14]	PM10		The risk of precocious puberty	OR	1.95 (1.33–2.85)†	Age, sex, SO2, NO2, CO, O3	69.77±41.07 μg/m3
	PM2.5				1.72 (1.01–2.92)†		38.81±26.36 μg/m3
Wronka et al. [8]	PM10	Low*MediumHigh	The risk of early menarche	OR	3.18 (2.29–4.69)†	Urbanization, mother's education, father's education, number of siblings, financial conditions	NA
	PM2.5				3.25 (2.34–4.80)†
	Benzene				1.11 (0.90–1.64)
	SO2				1.22 (1.01–2.14)
	NO				1.47 (0.65–1.35)
Zhao et al. [15]	PM10	10 μg/m3 increase in pollutant concentrations	Pubertal development at age 10 years assessed with estradiol and testosterone	OR	Female: 0.896 (0.379–2.122)Male: 0.821 (0.383–1.759)	Age, sex, body mass index, secondhand smoke exposure, time spent outside and in front of a screen, physical activity level, season, and time of the blood sampling, household income, parental education, maternal age at birth, single parent status	21.95±3.26 μg/m3
	PM2.5				Female: 0.163 (0.022–1.166)Male: 1.089 (0.156–7.605)		14.76±2.13 μg/m3
	NO2				Female: 0.892 (0.581-1.369)Male: 1.152 (0.768–1.728)		22.03±3.86 μg/m3
	O3				Female: 0.900 (0.605–1.339)Male: 0.830 (0.573–1.203)		69.18±4.9 μg/m3
Jung et al. [9]	PM10	1 μg/m3 increase in PM10	The risk of early menarche	OR	1.08 (1.04–1.12)†	Body mass index, city size, household income level, maternal age at menarche, second-hand smoke exposure at home	NA
Huang et al. [16]	PM10	SD increase in pollutants	Pubertal stage at age 11 years assessed with Tanner stage	Mean difference in Tanner stage	FemaleIn utero: −0.05 (−0.08 to −0.02)†Infancy: −0.03 (−0.06 to −1.2)†	Neighborhood and household income per person, mother's migration status, highest parental educational level, age, maternal age at birth, parity, maternal smoking	NA
	SO2				MaleIn utero: −0.03 (−0.05 to −0.01)†Childhood: −0.06 (−0.08 to −0.04)†
	NO				Statistically insignificant
	NO2				MaleIn utero: −0.03 (−0.04 to −0.02)†Childhood: −0.02 (−0.04 to −0.01)†
McGuinn et al. [17]	Traffic metrics	Distance to road (meters)	Pubertal stage at 6−8 years assessed with Tanner stage	TR	Pubarche: 0.96 (0.93–0.99)†Thelarche: 0.99 (0.97–1.02)	Race/ethnicity, household income, girl's cotinine level	NA

PM, particulate matter; SO₂, sulfur dioxide; NO₂; nitrogen dioxide; CO, carbon monoxide; O₃, ozone; TR, time ratio; NA, not applicable.
Low: annual pollutant values and the number of days per year with exceedances were below the allowable limit; Medium: annual values below the permissible limit, but with the number of days exceeding the normal above the limit; High: included zones above the limit.
Statistically significant results.