Carbon Soot Exposure Induces Hepatic Injury, Inflammatory Response, and Anxiety-Like Behaviour in Wistar Rats

Background: Exposure to carbon soot particulate matter from crude oil combustion is a growing environmental health concern, particularly in oil-producing regions. While respiratory effects are well known, systemic impacts on liver structure, inflammation, and behaviour remain poorly understood. This study evaluated hepatotoxic, inflammatory and neurobehavioural effects of PM₁₀ carbon soot in Wistar rats. Methods: Forty male Wistar rats were assigned to control and three exposure groups (low: 2.131±0.207 mg/m³; moderate: 2.161±0.232 mg/m³; high: 2.278±0.221 mg/m³). Animals were exposed for 1 hour daily over 28 days. Liver tissues were collected at days 3, 7, 14, 21, and 28 from separate cohorts for histology (H&E) and tumor necrosis factor-alpha (TNF-α) ELISA. Anxiety-like behaviour was assessed using the elevated plus maze. Data were analyzed using one-way ANOVA with Tukey’s post-hoc test. Results: Histological examination revealed progressive hepatic injury characterized by hepatocyte degeneration, necrosis, sinusoidal dilation, vascular congestion, and inflammatory infiltration, with severity increasing with both exposure duration and concentration. TNF-α levels increased steadily across exposed groups. Early elevations were observed at day 3 in the moderate (11.40±0.40 pg/mL) and high exposure groups (13.85±0.35 pg/mL) compared to control (8.30±0.20 pg/mL), followed by marked increases at day 7 (40.65±1.15 and 71.75±3.45 pg/mL, respectively). By day 21, TNF-α levels further increased to 116.50±3.50 pg/mL (moderate) and 204.50±7.50 pg/mL (high), reaching peak values at day 28 (266.00±39.00 and 295.00±23.00 pg/mL, respectively), compared to control (59.25±8.25 pg/mL). The low exposure group also demonstrated elevated TNF-α levels at day 28 (119.00±2.00 pg/mL). Behavioural assessment showed reduced open arm entries (1.08±0.08 vs 1.33±0.21) and open arm duration (7.00±1.51 s vs 10.67±5.64 s), alongside decreased closed arm duration (194.10±20.50 s vs 236.55±1.53 s), indicating increased anxiety-like behaviour in exposed animals. Additional behavioural alterations included increased central square duration (39.10±22.70 s) and altered rearing activity (15.86±4.68 in the moderate exposure group). Conclusion: Carbon soot PM10 induces significant dose- and time-dependent hepatic injury, inflammatory activation, and anxiety-like behaviour. The atypical moderate-dose behavioural findings warrant further investigation. These results highlight systemic soot toxicity and indicate the need for environmental health interventions.