Figure 5.

Associations between daily fine particulate matter air pollution with aerodynamic diameter $\le 2.5\mathrm{\mu }\mathrm{m}$ (${\mathrm{PM}}_{2.5}$) levels (per interquartile range increase) over the last week of pregnancy and preterm birth, stratified according to below 25th percentile of glutathione-related oxidative potential (${\text{OP}}^{\text{GSH}}$) (left) and above the 75th percentile of ${\text{OP}}^{\text{GSH}}$ (right) in Ontario, Canada (2006–2012). Solid lines reflect point estimates, and gray areas reflect 95% confidence intervals. Models were adjusted for maternal age at delivery, marital status, maternal cigarette smoking during pregnancy, infant sex, parity, previous caesarean section delivery, maternal comorbidities (i.e., asthma, hypertension, type 1 and 2 diabetes mellitus, preeclampsia, and gestational diabetes), year of birth, month of birth, census dissemination-area (DA) median family income, census DA proportion of population who are visible minority, and census DA proportion of the adult female population aged 25–64 y old who completed postsecondary education, mean temperature, and mean relative humidity.