Background: The role of passive smoking on cervical carcinogenesis remains controversial. We investigated the association of passive smoking with the risk of cervical intraepithelial neoplasia (CIN) and cervical cancer.

Methods: The study recruited 1,322 women, aged 18–65 with normal cytology (n = 592), CIN1 (n = 420), CIN2/3 (n = 165), and cervical cancer (n = 145) from 2006 to 2009. This study is a cross-sectional analysis using the baseline data from the Korean human papillomavirus (HPV) cohort study. Detailed information on smoking behaviors and lifestyles were collected using questionnaires. Multinomial logistic regression analysis was performed to estimate multivariable-adjusted odds ratios (ORs).

Results: Passive smoking was not statistically related to the risk of CINs and cervical cancer. However, passive smoking among non-smokers was associated with higher CIN 1 risk (OR 1.53; 95% confidence interval [CI], 1.07–2.18), compared to not passive smoking, after adjusting for demographic factors, lifestyles, and oncogenic-HPV infection status. CIN 1 risk increased with longer time exposed to passive smoking (P for trend <0.0003). Multivariate odds of <2 hours/day of passive smoking and that of ≥2 hours/day of passive smoking were 2.48 (95% CI, 1.49–4.14) and 2.28 (95% CI, 1.21–4.26) for CIN 1, compared to not passive smoking.

Conclusions: This study found that passive smoking among non-smoking women is associated with the risk of CIN 1.