Polycyclic aromatic hydrocarbons (PAHs) are harmful combustion byproducts with carcinogenic and mutagenic properties, and their carcinogenic potential persists in indoor environments. Vulnerable populations, particularly children, are at heightened risk of exposure. This study quantified schoolchildren’s exposure to fine particulate matter-bound PAHs (PM2.5-bound PAHs) in five urban classrooms between April 2024 and March 2025 using gas chromatography-mass spectrometry (GC-MS). Total PAH concentrations ranged from 1,140 to 1,470 ng/m³, with total toxic equivalent quotient (TEQ) values of 0.172-0.251 ng/m³, primarily driven by benzo[a]pyrene (B[a]P) and dibenzo[a,h]anthracene (DahA), which accounted for 62-68% of ETEQ. Pediatric incremental lifetime cancer risk (ILCR) estimates (2.47 – 3.6 * 10 ^ – 7) indicated low risk (<10 threshold) but were 1.75 times higher than adult estimates Regression models effectively predicted ∑TEQ (R ^ 2 = 0.958) and ILCR (R ^ 2 = 0.982) with 5-fold cross-validation confirming robustness (R²_cv = 0.92-0.94). K-means clustering \ k = 2 ; Silhouette score = 0.479) revealed compounddominated -exposure patterns. These findings highlight the need for targeted policy interventions, including improved ventilation and emission controls, to protect children’s health in indoor environments.

This study’s main objective is to ascertain whether river samples taken from four separate locations in Malaysia’s Terengganu state are contaminated with heavy metals. All samples were dried at 80 °C for a full day in order to measure their moisture content. The range of the water content was 70-77%. To determine the content of heavy metals, triplicate samples were assessed using an Atomic Absorption Spectrophotometer (AAS). All solid samples were completely digested for three hours at 120 °C using an oven and Teflon beakers. Lead and zinc were discovered to be more prevalent in sediments than other elements. Additional factors include pH, BOD, COD, DO, LOI, TN, and TP. Total nitrogen and phosphorus concentrations are highest in samples taken from locations near farms and municipal locations. With the exception of a few instances where it surpassed the limit, the concentration was generally below the acceptable level limit established for the water and sediment rules.