Assessment of volatile organic compounds in Lagos lagoon, Lagos State, Nigeria: A quantitative evaluation and benchmark against global standards

Abstract

The Lagos Lagoon, particularly the Makoko axis, is a vital aquatic resource that supports fisheries, domestic water use, transportation, and ecological balance in Lagos State. However, increased anthropogenic activities ranging from industrial discharge to domestic and agricultural runoff have raised significant concerns over its water quality. This study quantitatively evaluated thirty-three volatile organic compounds (VOCs) in the Lagoon to determine their concentration, potential sources, and environmental and public health implications. VOCs, which include a broad class of organic pollutants such as halogenated hydrocarbons and aromatic compounds, are known for their toxicity, persistence, and bio accumulative nature. Many VOCs are regulated due to their carcinogenic and endocrine-disrupting properties. Despite their hazardous profile, there is limited data on their presence in the Lagos Lagoon. This study aimed to fill this gap using an analytical method and employing global standards for result comparison. Sampling was conducted in November 2024 using the US EPA equilibrium headspace method, with subsequent analysis carried out via gas chromatography (GC) coupled with flame ionization detection (FID). Results revealed that dissolved oxygen (DO) level was 1.72 mg/L, while salinity was 7.88 ppt. This result suggested notable tidal influence from the Atlantic Ocean. The total average VOC concentration was 20.46 ± 0.07 mg/L. Bromoform emerged as the most abundant compound, with concentrations reaching 7.7640 ± 0.1520 mg/L across many sites. Of particular concern was the presence of 1,2-dibromochloropropane (DBCP), a banned substance, detected at 4.492 mg/L. This value is far above the US EPA permissible limit of 0.0002 mg/L. Other halogenated compounds such as 1,4-dichlorobenzene, hexachlorobenzene, and tetrachloroethane were also present at elevated levels, pointing to significant pollution inputs from industrial solvents, disinfectant by-products, agricultural chemicals, and fuel-related activities. These findings suggest that the Lagoon is undergoing severe contamination from anthropogenic sources, primarily industrial discharge, domestic waste, and agricultural runoff. The elevated levels of VOCs not only degrade water quality but also pose risks to aquatic biodiversity and human health through bioaccumulation and water contact. In conclusion, the Lagos Lagoon at Makoko is experiencing critical VOC pollution, far exceeding global safety benchmarks. Immediate intervention is required to mitigate further degradation. It is recommended that local and federal environmental authorities enforce stricter effluent regulations, establish continuous monitoring programs, and initiate public awareness campaigns. Furthermore, the introduction of wastewater treatment facilities and stricter control of agricultural chemical usage near the Lagoon should be prioritized to protect this vital water body and ensure long-term sustainability.