BACKGROUND Air pollution is both a sensory blight and a threat to human health. Inhaled environmental pollutants can be naturally occurring or human-made, and include traffic-related air pollution (TRAP), ozone, particulate matter (PM) and volatile organic compounds, among other substances, including those from secondhand smoking. Studies of air pollution on reproductive and endocrine systems have reported associations of TRAP, secondhand smoke (SHS), organic solvents and biomass fueled-cooking with adverse birth outcomes. While some evidence suggests that air pollution contributes to infertility, the extant literature is mixed, and varying effects of pollutants have been reported. OBJECTIVE AND RATIONALE Although some reviews have studied the association between common outdoor air pollutants and time to pregnancy (TTP), there are no comprehensive reviews that also include exposure to indoor inhaled pollutants, such as airborne occupational toxicants and SHS. The current systematic review summarizes the strength of evidence for associations of outdoor air pollution, SHS and indoor inhaled air pollution with couple fecundability and identifies gaps and limitations in the literature to inform policy decisions and future research. SEARCH METHODS We performed an electronic search of six databases for original research articles in English published since 1990 on TTP or fecundability and a number of chemicals in the context of air pollution, inhalation and aerosolization. Standardized forms for screening, data extraction and study quality were developed using DistillerSR software and completed in duplicate. We used the Newcastle-Ottawa Scale to assess risk of bias and devised additional quality metrics based on specific methodological features of both air pollution and fecundability studies. OUTCOMES The search returned 5200 articles, 4994 of which were excluded at the level of title and abstract screening. After full-text screening, 35 papers remained for data extraction and synthesis. An additional 3 papers were identified independently that fit criteria, and 5 papers involving multiple routes of exposure were removed, yielding 33 articles from 28 studies for analysis. There were 8 papers that examined outdoor air quality, while 6 papers examined SHS exposure and 19 papers examined indoor air quality. The results indicated an association between outdoor air pollution and reduced fecundability, including TRAP and specifically nitrogen oxides and PM with a diameter of ≤2.5 µm, as well as exposure to SHS and formaldehyde. However, exposure windows differed greatly between studies as did the method of exposure assessment. There was little evidence that exposure to volatile solvents is associated with reduced fecundability. WIDER IMPLICATIONS The evidence suggests that exposure to outdoor air pollutants, SHS and some occupational inhaled pollutants may reduce fecundability. Future studies of SHS should use indoor air monitors and biomarkers to improve exposure assessment. Air monitors that capture real-time exposure can provide valuable insight about the role of indoor air pollution and are helpful in assessing the short-term acute effects of pollutants on TTP.

Individual differences in temperament (e.g., negative emotionality) are robust early predictors of emotional and behavioral health. Although temperament is often conceptualized as relatively stable across the lifespan, evidence suggests that it may change over time as a function of social context. Extant studies have been limited by cross-sectional or short-term longitudinal designs that have precluded tests of stability as well as factors that may influence stability across developmental periods. In addition, few studies have tested the impact of social contexts that are common for children living in urban and under-resourced environments, such as exposure to community violence. In the present study we hypothesized that levels of negative emotionality, activity, and shyness would decrease across development from childhood to mid-adolescence as a function of early exposure to violence in the Pittsburgh Girls Study, a community study of girls enriched for families living in low-resourced neighborhoods. Temperament was assessed by parent- and teacher-report on the Emotionality Activity Sociability Shyness Temperament Survey in childhood (5–8-years-old), early-adolescence (11-years-old), and mid-adolescence (15-years-old). Violence exposure (e.g., victim of or witness to violent crime, exposure to domestic violence) was assessed annually via child and parent report. Results showed that on average, combined caregiver and teacher reports of negative emotionality and activity level exhibited small but significant reductions from childhood to adolescence, whereas shyness remained stable. Violence exposure in early adolescence predicted increases in negative emotionality and shyness by mid-adolescence. Violence exposure was not associated with stability of activity level. Our findings suggest that exposure to violence, particularly in early adolescence, amplifies individual differences in shyness and negative emotionality, underlying an important pathway of risk for developmental psychopathology.