Assessment of differences in urinary heavy metal concentrations and environmental factors between children with autism spectrum disorder and neurotypical controls

Heavy metals are associated with autism spectrum disorder (ASD), interfering with neurodevelopment. This study assessed differences in urinary heavy metal concentrations and environmental risk factors between children with ASD and neurotypical controls. A hospital-based case-control study, including 25 ASD patients and 25 age- and sex-matched neurotypical controls aged 5-14 years at the Psychiatry Clinic of Cairo University's Kasr Al Ainy Hospital, was conducted between September and December 2024. ASD was diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders criteria, and symptom severity was evaluated using the Childhood Autism Rating Scale, Second Edition. Morning urine samples were collected and analyzed for lead (Pb), mercury (Hg), arsenic (As), and copper (Cu) via inductively coupled plasma optical emission spectroscopy with concentrations standardized to creatinine levels. Guardians completed a questionnaire addressing sociodemographic characteristics and environmental, prenatal, and postnatal exposures. Children with ASD had significantly higher rates of prenatal complications (p = 0.0002) and postnatal complications (p < 0.0001), as did those with prenatal pesticide exposure (p = 0.0006). Aluminum pan usage was more common among children with ASD (p < 0.0001). The urinary levels of As (p = 0.011) and Hg (p = 0.021) were significantly higher in the ASD group, whereas those of Pb and Cu were not significantly different (p > 0.05). Secondhand smoke exposure was the strongest predictor of ASD status (OR = 10.79, p = 0.034). Arsenic and mercury exposure, together with environmental risk factors, may contribute to ASD pathogenesis and highlight the importance of environmental risk assessment in pediatric populations.