iRRRd: The impacts of outdoor and indoor air quality and temperature during pregnancy and early infancy on Rohingya and Bangladeshi infants’ temperament

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Temperament is conceptualized as an individual's innate, biologically-based, and consistently expressed style of emotional reactions and behavioral patterns that are present from birth, forming the foundation for personality. Yet, considerable evidence shows that experiences of environmental adversity in early life can shape the trajectories of temperament development in infancy and childhood, with potential implications for lifelong health and well-being. In this research, we will examine the predictive associations of prenatal and postnatal outdoor and indoor environmental conditions on the development of temperament in the first 6 months. The Infant Temperament Scale has been shown to be a valid and reliable measure of infant temperament in Majority World countries (Murray-Kolb et al., 2014; Pendergast et al., 2018), including Bangladesh (Tofail et al., 2019). Extensive research conducted in both high-income countries (HICs) and low- and middle-income countries (LMICs) have documented the adverse effects of air pollution and extreme heat on physical and mental health across the lifespan (Cuartas et al., 2024, 2026). This includes exposure to adverse environmental conditions in the prenatal and infancy periods, when the brain and other biological systems are undergoing rapid development and may be most susceptible to environmental risks. Increased exposure to air pollutants during pregnancy, as indexed both by climatic indicators of the external environment (Buthmann et al., 2026; Li et al., 2026; McGuinn et al., 2024) and assessment of local indoor air quality (DeSerisy et al., 2026; Liu et al., 2022, 2023), as well as postnatal exposure in infancy and early childhood (Cuartas et al., 2024; Odo et al., 2023; Rana et al., 2022), has been found to predict increased likelihood of evincing socioemotional, cognitive and behavioral difficulties as early as 6 months. Although associations between prenatal exposures to environmental adversity and subsequent well-being have been documented for exposures across all three trimesters, some studies suggest that such exposure in the second and third trimesters may convey particularly high risk (Bansal et al., 2021; Rahman et al., 2022; Lin et al., 2014). Yet, few if any analyses have accounted for both prenatal and postnatal exposures to both climatic/outdoor environment and indoor air quality in their analyses of impacts on infant adjustment. Whether exposures from conception through infancy are likely to influence temperamental development in additive, compounding, or indirect ways is unclear. An associated aspect of environmental conditions that frequently has been examined in relation to temperament is seasonality. More specifically, several studies have shown that when pregnancies predominantly encompass winter months, infants and young children are more likely to evince negative emotionality, irritability, fearfulness or shyness, and poor effortful control, compared to children for whom pregnancies were predominantly within summer months (Asano et al., 2016; Carskadon & Acebo, 2002; Grotmaker et al., 1997). Differences in hours of sunlight, and potential impacts of melatonin and other neurohormones and neurotransmitters, have been the most common explanation for these seasonal patterns, which is plausible given that these studies have been conducted in regions far enough from the equator that length of daylight in winter versus summer differs by several hours. For countries and regions in the tropical and equatorial zones, however, seasons vary less in sunlight than they do in such climatic conditions as heat, air quality and rainfall. Such is the case for Bangladesh, when the worst air quality tends to occur during the drier, cooler winter months (approximately November – March), but the most excessive heat occurs in summer prior to the onset of monsoons (approximately April – June). Excessive heat during pregnancy and infancy also has been identified as a risk factor for infants’ and young children’s well-being (Cuartas et al., 2025, 2026), but how heat and air quality together affect infant development has rarely been examined. We will examine this within the current analyses. This study will use the Infant Temperament Scale to examine how climatic environmental factors, including seasonal variation in exposure to climatic adversities (high temperatures; air pollution) and indoor air quality, during pregnancy and the first 6 months postnatal, are associated with temperamental difficulty of infants born to displaced Rohingya families living in refugee camps in Bangladesh, and Bangladeshi families in towns adjacent to the camps. Prenatal and postnatal data were collected from all mothers; archival administrative databases provided daily data on temperature and air quality indicators for the study area throughout the period of data collection; indoor air quality was assessed at 1 or 2 prenatal visits and at 1 and 6 month postnatal visits; and infant temperament was measured by mother-report at 1 and 6 months. Outdoor conditions were obtained from NASA POWER (NASA Prediction of Worldwide Energy Resources) and CAMS EAC4 (Copernicus Atmosphere Monitoring Service ECMWF Atmospheric Composition Reanalysis 4) for the period encompassing all mothers’ pregnancies and infants’ first 6 months. Air quality within homes was assessed using TemTop monitors and caregiver report of type of cooking fuel and smoking in the home. Mothers’ reports on the Infant Temperament Scale at 1 and 6 months provided data on six dimensions of infant temperament: activity, positive emotionality, negative emotionality, sociability, attention, and soothability. Temperamental difficulty is expected to be reflected in mother reports of greater negative emotionality and activity, dimensions indicative of more reactivity and poorer regulation, and less positive emotionality, sociability, attention and soothability, dimensions indicative of better regulation and more easy-going temperament. Both specific temperament dimension scores and global temperament scores will be examined. Findings from this study will provide important information on how extreme environmental conditions, which are becoming more prevalent within the Anthropocene epoch of rapid climate change, affect infants’ early temperament, a key foundation for, and predictor of, subsequent social-emotional and behavioral well-being. 6. 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