Figure 4.

Concentration–response curves using natural cubic splines with 3 degrees of freedom for the association between exposure to fine particulate matter air pollution with aerodynamic diameter $\le 2.5\mathrm{\mu }\mathrm{m}$ (${\mathrm{PM}}_{2.5}$) during the first trimester and term low birth weight, stratified according to below 25th percentile of glutathione-related oxidative potential (${\text{OP}}^{\text{GSH}}$) (solid line) and above the 75th percentile of ${\text{OP}}^{\text{GSH}}$ (dashed line) in Ontario, Canada (2006–2012). Dotted lines 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, census DA proportion of the adult female population aged 25–64 y old who completed postsecondary education, and gestational age.