A study of the biological exposure characteristics of vehicle exhaust and its toxic effects on plants and traffic workers to propose plant-based solutions for pollution reduction

Abstract

Background: Baghdad’s vehicle fleet (>7 million) has contributed to substantial traffic-related pollution, raising concerns about occupational heavy-metal exposure among traffic personnel. Objectives: To determine salivary concentrations of lead, cadmium, and nickel in traffic-exposed workers; calculate the Air Pollution Tolerance Index (APTI) and Bioaccumulation Factor (BAF) in Eucalyptus camaldulensis and Nerium oleander; and develop the Pollution Burden Index (PBI) and Phytoremediation Efficiency Index (PEI). Methodology: A cross-sectional biomonitoring study was conducted at four high-volume (>3,000 veh/hr) and one low-volume intersection. Saliva was collected from 120 male volunteers (n = 24/site; mean age 38.4±9.7 years). Pb and Ni were analyzed by GFAAS and Cd by ICP-MS; MDA and GSH were measured spectrophotometrically. Leaf samples underwent EPA 3050B acid digestion. Structural equation modeling (SEM; n = 120) assessed relationships among exposure, plant physiology, and biomarkers. Results: Salivary metals were 5–12-fold higher at traffic sites (p < 0.001). At R1, MDA reached 0.82±0.09 μmol/L (2.05× upper reference), while GSH fell to 22% of the lower reference. PBI explained 94.3% of MDA variance (r = 0.971) and 91.8% of GSH variance (r = −0.958). E. camaldulensis (APTI = 22.4; PEI = 2.76) outperformed N. oleander (APTI = 13.7; PEI = 0.68). Conclusions: Traffic exposure was associated with elevated salivary metals and oxidative-stress alterations. E. camaldulensis showed greater phytoremediation potential, with model-based estimates suggesting removal of ~4.4 tonnes of combined Pb, Cd, and Ni annually.