Biological Test Used in the Assessment of Cytotoxicity and Genotoxicity of Olusosun Landfill: The Largest and Unregulated Landfill in Nigeria

Indiscriminate disposal of solid wastes into the environment generates landfill gases and leachates. Leachate, a mixture of deleterious substances including metals, inorganic and organic compounds, particulate matters, radioactive elements, and microorganisms, contaminates soils and underground and surface water resources increasing risk to human and wildlife health. This study is a compendium of studies on the cytotoxic and genotoxic assessment of Olusosun landfill (the largest unregulated landfill in African). Leachates emitted from Olusosun solid waste landfill induced cytotoxicity and DNA damage via direct and indirect mechanisms. Different biomarkers of genotoxicity were used to evaluate the cytotoxic and genotoxic potentials of OSL leachates. Biomarkers of chromosome aberration, micronucleus assay, comet assay, sperm head abnormality test and toxicogenomic signatures, were assessed in somatic and germline cells of exposed organisms. The mechanisms of DNA damage include generation of free radicals and oxidative stress, inhibition of DNA repair process, alkylation on DNA molecules that may lead to chromosome breakage, down-regulation of transcriptional genes related to apoptotic expressions, and increased DNA fragmentation in cells and tissue. The damaged DNA can increase genome instability and genetic related diseases. Heavy metals, physico-chemicals and organic substances present in the leachates are known mutagens, genotoxin and carcinogens. It is suggested that proper landfill management be instituted in various countries to avert exposure to landfill emissions.