ENVIRONMENTAL MANAGEMENT AND TOXICOLOGY

Background: N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine-quinone (6PPD-quinone or 6PPD-Q), a pervasive transformation product of tire-wear antioxidants, has been identified as a highly toxic contaminant in urban stormwater runoff, responsible for acute mortality in sensitive salmonid fish. However, its sublethal, chronic, and mechanistic toxicity on non-salmonid freshwater species, such as the African Catfish (Clarias gariepinus), remains less understood. Objective: This study investigates the toxic effects of 6PPD-Q on the antioxidant defense system—specifically glutathione (GSH), glutathione peroxidase (GPx), and superoxide dismutase (SOD)—in Clarias gariepinus under sub-chronic exposure. Methodology: Clarias gariepinus fingerlings were exposed to environmentally relevant and higher concentrations of 6PPD-Q [0, 0.5, 1.0, 5.0 g/L] for a period of 28 days under controlled conditions. Liver tissues were analyzed for GSH levels, GPx activity, and SOD activity at 7, 14, and 28 days of exposure.
Results: 6PPD-Q exposure induced significant dose- and time-dependent oxidative stress in C. gariepinus. Initial exposure (days 7–14) resulted in a compensatory increase in SOD and GPx activities and GSH levels. However, prolonged exposure (day 28) to higher concentrations (1.0–5.0 g/L) led to a significant decrease in GSH levels and inhibited GPx and SOD activities, indicating an overwhelming of the antioxidant defense system. Conclusion: The results demonstrate that 6PPD-Q is highly toxic to Clarias gariepinus, inducing severe oxidative stress that disrupts key detoxification pathways. The inhibition of GSH, GPx, and SOD suggest that 6PPD-Q can trigger severe hepatic cellular damage and long-term health risks in this species, necessitating tighter monitoring of tire-derived pollutants in freshwater ecosystems.

Presence of oil in the soil – plant microenvironment influences normal chemistry of soil wherein the release of nutrient and uptake and also the quantity of water is reduced. The present study assessed the effect of oil contaminated soil on the growth and development of maize (Zea mays) over a period of 38 days. Result of the study revealed that oil contaminated soil affect the growth of maize in varying degree. The growth in height, root length and leaf area was evaluated using soil contaminated with oil at 25%, 50%, 75% 100% concentration and a control sample. Result showed that there was gradual decrease in height of maize with increasing concentration and the control sample recorded the greatest height. At 10 to 38 days after planting (DAP) lowest growth in height was observed in 100% sample. Also, there was a steady decrease in length of root as the concentration increases while the control sample had the greatest length throughout the experiment. The leaf area of maize gradually decreases as the concentration increases. The control sample also had the greatest leaf area. Lowest growth in leaf area at 10 to 38 days after planting (DAP) was observed in the 100% concentration. This shows that soil contamination with oil affects plants growth and development. It is recommended that care should be taken during oil exploration, exploitation, processing, storage and distribution to avoid contamination of soil by oil which will affect crops leading food shortage. Furthermore, remediation should be carried out on soils that have been previously contaminated.

Major contributions to the pollution in the atmosphere are Nitrogen dioxide (NO2) and Sulphur dioxide (SO2) from cement factories as well as other industrial activities in Urban and Rural areas. The study area covers Ibese, Paplanto, Abeokuta, Ewekoro and other rural areas as they play host to either cement factories or congested urban. This research compared the amount of NO2 and SO2 released into the atmosphere at Ibese, Papalanto and Abeokuta. Sentinel 5P data for the study area was used to monitor these pollutants. Google earth engine editor was used to extract the pollutants over the study area. The duration considered was a 4-month interval within year 2019 to 2021 which was used to present 3 spatial maps per year resulting in a total of 9 maps for both pollutants. SO2 concentration ranged between -0.000161 to 0.0000782; -0.000206 to 0.000162; 0.000194 to 0.000228, for 2019, 2020 and 2021 respectively. NO2 concentration ranged between 0.0000459 to 0.0000846, 0.0000491 to 0.0000947, 0.0000565 to 0.000122 mol/m2 for 2019, 2020 and 2021 respectively. The spatial distribution for both pollutants were regrouped into 4 classes namely low, moderate, high and very high. Ibese fell once within the low class, seven times within the moderate class, five times each within the high and very high class respectively considering both the NO2 and SO2 maps. Papalanto fell twice within the low class, once within the moderate class, six times within the high class and eight times within the very high class. Abeokuta fell six times within the moderate class and twelve times within the high class. The most dominant zone is the moderate zone followed by the high zone for SO2 and NO2 between 2019 and 2021. The frequency of occurrence of Papalanto and Ibese within the peak zone of SO2 and NO2 was very high when compared to the frequency of occurrence of Abeokuta which never fell beyond the high zone of either pollutant. This was attributed to the cement factory working nonstop
located within Papalanto and Ibese.