Environmental Assessment of Heavy Metals and Hydrocarbons in Waste Lubricants at Ladipo Auto-Mechanics Market, Lagos, Nigeria

Waste lubricants from automotive repair activities are an important yet under-regulated source of environmental contamination in urban markets. This study investigated the levels of heavy metals and hydrocarbons in waste lubricants from the Ladipo auto-mechanics market, Lagos, Nigeria a major hub for vehicle maintenance and parts trade. A total of 30 waste lubricant samples were collected during both wet and dry seasons from randomly selected workshops and analysed for lead (Pb), cadmium (Cd), chromium (Cr), zinc (Zn), copper (Cu), nickel (Ni), total petroleum hydrocarbons (TPH), and polycyclic aromatic hydrocarbons (PAHs) using Atomic Absorption Spectrophotometry (AAS) and Gas Chromatography–Mass Spectrometry (GC–MS). Mean concentrations (mg/kg) of Pb (85.3), Zn (320.4), Cu (112.7), Ni (26.5), and Cd (2.4) exceeded Nigerian Department of Petroleum Resources (DPR) intervention limits in over 70% of samples, with wet season values generally higher than dry season levels. TPH levels (mean: 125,000 mg/kg) were 25–40 times above DPR soil target values. Spatially, workshops closer to drainage channels showed higher contaminant loads, suggesting runoff transport into surrounding soils and water bodies. The contamination profile indicates significant ecological and human health risks, especially via dermal contact and food chain transfer. Urgent regulatory enforcement, waste oil collection systems, and public awareness are recommended to mitigate further degradation of the local environment.