Trace Element Dysregulation and Detoxification Dysfunction in Autism Spectrum Disorder: A Urinary Biomarker Study with Element Ratio Analysis

Background: Autism spectrum disorder (ASD) arises from complex gene–environment interactions. While trace element abnormalities have been studied, associations with autism severity remain inconsistent. Ratios indicating detoxification balance, rather than single toxic elements, may better reflect severity. Objective: To examine the relationships between urinary trace element levels, detoxification-related element ratios, and autism severity measured by the Childhood Autism Rating Scale (CARS). Methods: In a cross-sectional study of 168 participants (103 ASD, 65 controls), thirty urinary trace elements were quantified by ICP-MS. ASD patients were stratified by CARS into subthreshold ASD (n = 29), mild–moderate ASD (n = 36), and severe ASD (n = 38). Analyses included Mann–Whitney U, Kruskal–Wallis, and Spearman correlation tests, focusing on Li/Pb, Cu/Pb, and Cr/Pb ratios. Results: Individual elements showed weak associations with CARS; lead correlated positively (ρ = 0.209, p = 0.035) and lithium inversely (ρ = −0.194, p = 0.051). In contrast, element ratios showed stronger links: Li/Pb (ρ = −0.349, p = 0.0003), Cu/Pb (ρ = −0.320, p = 0.0011), and Cr/Pb (ρ = −0.209, p = 0.035). Severe ASD exhibited modest 90th-percentile elevations for toxic elements but high heterogeneity. Conclusions: Single-element levels showed limited associations with ASD severity. Element ratios, particularly Li/Pb, showed stronger statistical associations than individual elements in this cross-sectional dataset; however, these findings should be interpreted as candidate correlates rather than causal or clinically validated biomarkers.