BACKGROUND: Air pollution may cause specific genetic or epigenetic abnormalities and lead to the development of uterine fibroids (UFs). However, there have been limited studies evaluating the relationship between air pollutant exposure and the development of UFs. METHODS: We conducted a 10-year cohort-based case-control study in Taiwan from 2001 to 2010 using National Health Institute Research Database (NHIRD) to assess the association between air pollution and the UFs development among Taiwanese women. The case group consisted of 11,028 women newly diagnosed with UFs during the study period and the control group was 44,112 women aged 25-45 years using density sampling with a 1:4 matching on the date of birth from 224,675 women in 2001-2010. The average age of onset was 36+/-4.37 years old. Daily concentrations of PM2.5 were estimated by linear mixed-effects model integrating aerosol optical depth (AOD) and meteorological variables; daily concentrations of O3, CO, NO2 and SO2 were calculated by the Inverse Distance Weighting (IDW). The annual cumulative exposure to air pollutants during the study period was calculated corresponding to residential zip codes. RESULTS: In the conditional logistic regression adjusting for confounders, the adjusted odds ratio (aOR) for UFs per 10mug/m(3) increase in PM2.5 was 1.105 (95% confidence interval: 1.069, 1.141), per 10ppb increase in O3 was 1.075 (95% confidence interval: 1.039, 1.113), respectively. CONCLUSIONS: Our study suggests that exposure to PM2.5 and O3 may increase the risk of developing UFs. Further studies are needed to confirm this novel finding.