Significant Emissions of Phenol and Alkylphenols from Heavy-Duty Diesel Vehicles, Their Dynamic Dispersion, and Human Exposure in Near-Road Microenvironments

This study identified and characterized a series of alkylphenols (APs) emitted from heavy-duty diesel vehicles (HDDVs) using two-dimensional gas chromatography mass spectrometry, simulated their near-road dispersion, and estimated population exposure in near-road microenvironments. It was revealed that APs, including nonyl- and octyl-substituted homologs, represented a non-negligible fraction of semi-volatile organic emissions with diverse structural and toxicological features. A systematic reduction in AP emissions was observed with the progressive tightening of emission standards, decreasing from 28.5–35.1 mg km–1 to 6.6–16.8 mg km–1, and further to 2.0–4.7 mg km–1 for China IV, V, and VI vehicles, respectively. Structural analysis further suggested that APs with bulky alkyl or bisphenol-like moieties exhibit stronger endocrine-disrupting and potential carcinogenic characteristics. Dispersion modeling revealed distinct diurnal concentration patterns, with maximum levels around 07:00 a.m. resulting from morning rush-hour traffic emission. This overlap between peak emissions and high population density indicated a critical exposure window for commuters and roadside residents. The estimated daily intakes (EDIs) of near-road APs via air inhalation were 1.75, 2.09, 1.21, 0.76, and 0.74 ng (kgbw day)−1 for infants, toddlers, children, teenagers, and adults, respectively, which were substantially higher than EDIs reported under ambient environments, indicating strong exposure risks, particularly for toddlers with higher metabolic and respiratory rates. These findings highlight the emerging significance of APs as traffic-related semi-volatile pollutants with health relevance and underscore the need for their inclusion in vehicular emission monitoring networks, toxicological evaluation, and source-specific regulatory frameworks.