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Spontaneous abortion (SAB), defined as a pregnancy loss before 20 weeks of gestation, affects up to 30% of conceptions, yet few modifiable risk factors have been identified. We estimated the effect of ambient air pollution exposure on SAB incidence in Pregnancy Study Online (PRESTO), a preconception cohort study of North American couples who were trying to conceive. Participants completed questionnaires at baseline, every 8 weeks during preconception follow-up, and in early and late pregnancy. We analyzed data on 4643 United States (U.S.) participants and 851 Canadian participants who enrolled during 2013–2019 and conceived during 12 months of follow-up. We used country-specific national spatiotemporal models to estimate concentrations of particulate matter <2.5 μm (PM 2.5), nitrogen dioxide (NO 2), and ozone (O 3) during the preconception and prenatal periods at each participant's residential address. On follow-up and pregnancy questionnaires, participants reported information on pregnancy status, including SAB incidence and timing. We fit Cox proportional hazards regression models with gestational weeks as the time scale to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association of time-varying prenatal concentrations of PM 2.5 , NO 2 , and O 3 with rate of SAB, adjusting for individual- and neighborhood-level factors. Nineteen percent of pregnancies ended in SAB. Greater PM 2.5 concentrations were associated with a higher incidence of SAB in Canada, but not in the U.S. (HRs for a 5 μg/m3 increase = 1.29, 95% CI: 0.99, 1.68 and 0.94, 95% CI: 0.83, 1.08, respectively). NO 2 and O 3 concentrations were not appreciably associated with SAB incidence. Results did not vary substantially by gestational weeks or season at risk. In summary, we found little evidence for an effect of residential ambient PM 2.5 , NO 2 , and O 3 concentrations on SAB incidence in the U.S., but a moderate positive association of PM 2.5 with SAB incidence in Canada. • We found a positive association of ambient PM 2.5 concentrations with spontaneous abortion in Canada, but not the USA. • NO 2 and O 3 concentrations were not appreciably associated with rate of SAB. • Results were relatively consistent across season and weeks of gestation. • Protection of pregnant individuals from air pollutionis an important measure to safeguard maternal and fetal health. [ABSTRACT FROM AUTHOR]

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals used in commercial and consumer goods. Black women are underrepresented in studies of PFAS exposure. We performed a cross-sectional analysis of correlates of plasma PFAS concentrations among 1499 Black women aged 23–35 participating in the Study of Environment, Lifestyle, and Fibroids (SELF), a Detroit-based cohort study. At baseline (2010–2012), participants provided questionnaire data on socio-demographics; behaviors; diet; and menstrual, contraceptive, and reproductive histories. Using mass spectrometry in non-fasting plasma samples collected at enrollment, we quantified several PFAS, including perfluorohexane sulfonate (PFHxS), perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), perfluorononanoate (PFNA), perfluorodecanoate (PFDA), perfluoroundecanoate (PFUnDA), and 2-N-methyl-perfluorooctane sulfonamido acetate (MeFOSAA). We used linear regression to calculate percentage differences (%D) and 95 % confidence intervals (CIs) for associations between selected correlates and PFAS concentrations, adjusting for all other correlates. PFHxS, PFOS, PFOA, and PFNA were detected in ≥97 % of women; PFDA in 86 %; MeFOSAA in 70 %; and PFUnDA in 52 %. Age, income, education, and intakes of water, alcohol, and seafood were positively associated with several PFAS. Current smoking was positively associated with MeFOSAA. Body mass index was inversely associated with most PFAS, except PFHxS. Strong inverse associations (%D; 95 % CI) were observed between parity (≥3 vs. 0 births) and PFHxS (−34.7; −43.0, −25.1) and PFOA (−33.1; −39.2, −26.3); breastfeeding duration (≥6 months vs. nulliparous) and PFOA (−31.1; −37.8, −23.7), PFHxS (−24.2; −34.5, −12.3), and PFOS (−18.4; −28.3, −7.1); recent birth (<2 years ago vs. nulliparous) and PFOA (−33.1; −39.6, −25.8), PFHxS (−29.3; −39.0, −18.1), PFNA (−25.2; −32.7, −16.8), and PFOS (−18.3; −28.3, −6.9); and intensity of menstrual bleed (heavy vs. light) and PFHxS (−18.8; −28.3, −8.2), PFOS (−16.4; −24.9, −7.1), PFNA (−10.5; −17.8, −2.6), and PFOA (−10.0; −17.2, −2.1). Current use of depot medroxyprogesterone acetate (DMPA) was positively associated with PFOS (20.2; 1.4, 42.5), PFOA (16.2; 1.5, 33.0), and PFNA (15.3; 0.4, 32.4). Reproductive factors that influence PFAS elimination showed strong associations with several PFAS (reduced concentrations with parity, recent birth, lactation, heavy menstrual bleeding; increased concentrations with DMPA use). [ABSTRACT FROM AUTHOR]

Previous research indicates an association between higher-chlorinated polychlorinated biphenyls (PCBs) and type 2 diabetes (T2D). However, less is known about the extent to which PCB exposure in indoor air, composed primarily of lower-chlorinated PCBs, affects T2D risk. We assessed the association between indoor air exposure to PCBs in residential buildings and T2D incidence. The register-based 'Health Effects of PCBs in Indoor Air' (HESPAIR) cohort comprises 51,921 Danish residents of two residential areas with apartments built with and without PCB-containing materials (reference apartments). We assessed exposure status by combining register-based information on relocation history with extrapolated values of exposure based on PCB-measurements in indoor air from subsets of the apartments. T2D cases were identified in the Danish registers during 1977–2018. We estimated adjusted hazard ratios (HR) and 95% confidence intervals (CI) using Cox regression analyses with time-varying exposure. We identified 2737 incident T2D cases during the follow-up. Exposure to ≥3300 ng/m3 PCB × year (3rd tertile of PCB year) was associated with higher risk of T2D (HR 1.15, 95% CI 1.02–1.30) compared with exposure to <300 ng/m3 PCB × year (reference). However, among individuals with lower cumulated PCB year , the risk was similar to residents with exposure <300 ng/m3 PCB × year (300–899 ng/m3 PCB × year: HR 0.98, 95% CI 0.87–1.11; 900–3299 ng/m3 PCB × year: HR 0.96, 95% CI 0.83–1.10). We observed a marginally higher risk of T2D, but there was no evidence of an exposure-response relationship. The results should be interpreted with caution until confirmed in other independent studies of PCB exposure in indoor air. • Residents may be exposed to PCBs in indoor air in their private homes • Airborne PCB exposure has previously been associated with type 2 diabetes • PCB exposure in indoor air is associated with slightly higher type 2 diabetes risk [ABSTRACT FROM AUTHOR]