NEW YORK, August 22, 2025 — Individuals living in urban cities are experiencing the combined effect of increasing temperatures and poor air quality, often referred to as the urban heat dome. Pregnant mothers and their unborn children are especially at risk. New research from the City University of New York and Icahn School of Medicine at Mount Sinai suggests that the combined effect of summer heat and urban air pollution may trigger hormonal changes in children, with long term consequences on their behavioral development.
The study, published in Environmental Research , examined how combined environmental exposures during pregnancy affect children's hormone levels and behaviors years later. The findings suggest a biological pathway through which environmental-related stressors may influence mental health and well-being in children, particularly in urban communities with higher pollution levels.
Research Findings
"We're seeing that extreme heat and pollution are essentially programming children's stress responses before they're even born," said principal investigator Yoko Nomura , Ph.D., a Psychology professor at the City University of New York Graduate Center (CUNY Graduate Center) and Queens College . "Understanding these pathways could inform public health interventions and policies."
The study examined 256 children from birth through age 5, primarily from minority families in New York City. Researchers found that children whose mothers experienced combined heat and air-pollution exposure during pregnancy showed altered hormone levels and increased behavioral difficulties by ages 4 and 5.
"What makes this study unique is that we are able to explore how environmental exposures as early as conception may impact children's behavioral development" said Sameera Ramjan , MA, a Psychology doctoral student at the CUNY Graduate Center and second author on the study. "More importantly, we are interested in how the macro environment affects urban families on a daily basis, so that we can provide early interventions and inform policies."
Location and Timing Matter
The study revealed important differences based on pollution levels and the timing of exposure. In areas with higher pollution levels, first-trimester heat exposure was associated with elevated progesterone levels that persisted into early childhood. Children showed increased rates of anxiety, depression, and behavioral difficulties by age 5. However, these effects were not observed in areas with lower pollution levels.
"The findings suggest that pollution may amplify the effects of heat exposure on developing biological systems," Nomura explained. "This has particular relevance for urban communities that face both climate and air quality challenges."
Understanding the Biological Mechanism
The study found that changes in a hormone called progesterone may help explain how heat and air-pollution exposure during pregnancy lead to differences in children's behaviors. While progesterone normally supports healthy brain development, findings suggest that altered levels during critical developmental periods may influence long-term behavioral patterns.
"As we face rising temperatures due to climate change, understanding how heat exposure affects maternal and fetal health is increasingly critical," said Melissa Blum, a medical student at the Icahn School of Medicine at Mount Sinai and co-author on the study. "This research shows that the health impacts of extreme heat extend beyond immediate physical effects to influence child development in ways we're just beginning to understand."
Public Health Implications
The findings have potential implications for environmental health policy and clinical practice. As we experience more extreme heat and air quality remains a concern in many urban areas, understanding these relationships becomes increasingly important. Behavioral problems in early childhood can be warning signs for future mental health problems and can make it harder for children to succeed in the classroom. By identifying environmental risks early, there's a better chance to support children before these challenges take hold.
"This research addresses relevant public health issues and environmental justice among all New Yorkers," Nomura noted. "Communities that experience higher pollution levels may also be more vulnerable to increasing heat, creating compounded risks for child development. We need to ensure that families living in urban areas have access to clean air and protection from extreme heat."
Dr. Perry Sheffield, MD, MPH, the study's senior author and a pediatrician at the Icahn School of Medicine at Mount Sinai, emphasized the clinical relevance of the findings. "As a pediatrician, I see the behavioral challenges these children face in my practice. This research helps us understand that some of these issues may have environmental roots that begin before birth, which opens up new avenues for prevention and early intervention."
Future Directions
"Understanding these biological pathways opens up possibilities for targeted interventions," said Dr. Veronica Hinton, co-author and director of clinical training in clinical neuropsychology at CUNY. "The next step is to understand whether these effects persist into later childhood and adolescence, and to identify factors that might protect children from these environmental influences."
Sheffield noted the broader implications: "From a public health perspective, this work reinforces the importance of environmental health policies that protect pregnant people and developing children. The prenatal period represents a critical window where interventions can have lasting benefits."
These findings build on earlier work by members of the research team, which linked in utero exposure to extreme climate events and early-life heat to structural brain changes, including enlarged basal ganglia — regions involved in emotion regulation. Together, the evidence underscores how early environmental exposures may program biological systems in ways that shape long-term health.
About the Study
The research analyzed data from the Stress in Pregnancy Study (2009-2014), following children from birth through age 5. The study was supported by grants from the National Institute of Mental Health and the National Institute on Drug Abuse.
About the City University of New York Graduate Center
The CUNY Graduate Center is a leader in public graduate education devoted to enhancing the public good through pioneering research, serious learning, and reasoned debate. The Graduate Center offers ambitious students nearly 50 doctoral and master's programs of the highest caliber, taught by top faculty from throughout CUNY — the nation's largest urban public university. Through its nearly 40 centers, institutes, initiatives, and the Advanced Science Research Center, the Graduate Center influences public policy and discourse and shapes innovation. The Graduate Center's extensive public programs make it a home for culture and conversation.
