Systematic Review of Prenatal Exposure to PM2.5 and Its Chemical Components and Their Effects on Neurodevelopmental Outcomes in Neonates

Particulate matter with a diameter less than 2.5 µm (PM_2.5) and its chemical constituents—including ammonium (NH₄⁺), sulfate (SO₄²⁻), nitrate (NO₃⁻), organic carbon (OC), soil dust, and black carbon (BC)—have been increasingly recognized for their potential impact on fetal neurodevelopment. This systematic review aimed to synthesize current evidence on the relationship between prenatal exposure to PM_2.5 and its chemical components and neurodevelopmental outcomes in neonates, focusing on diagnoses such as autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD). Following PRISMA 2020 guidelines, a comprehensive literature search was conducted on PubMed and Embase databases from April to July 2025. Twenty-five studies meeting inclusion criteria were analyzed, of which sixteen addressed PM_2.5 exposure generally, and nine assessed specific chemical constituents. The findings indicate that increased exposure to PM_2.5, particularly during the third trimester, is associated with a higher risk of ASD. Additionally, prenatal exposure may adversely affect early neurodevelopmental domains including motor skills, problem-solving, and social interactions. Certain PM_2.5 components, notably sulfate ions (SO₄²⁻), were identified as important contributors to neurological health outcomes. These results underscore the importance of reducing prenatal exposure to PM_2.5 and its harmful constituents to protect neurodevelopment.