1 Nigerian Journal of Environment and Health 5 (2025) 01-10 Distribution of Organochlorine Pesticides in Nigerian Human Serum and Risk of Cancer: A case-control study Yemisi Tosin Awe 1* , Adedeji Ayodeji Onayade 2 , Mosudi Babatunde Sosan 3 , Oluwatosin A. Adedeji 4 , John Adekunle Oyekunle 5 , Olusegun Isaac Alatise 6 , Olalekan Olasehinde 6 and Adewale Adisa 6 1 Institute of Ecology and Environmental Studies, Obafemi Awolowo University, Ile-Ife, Nigeria 2 Institute of Public Health, Obafemi Awolowo University, Ile-Ife, Nigeria 3 Department of Crop Production and Protection, Obafemi Awolowo University, Ile-Ife, Nigeria 4 Department of Environmental Management and Toxicology, University of Ilesa, Ilesa, Nigeria 5 Department of Chemistry, Obafemi Awolowo University, Ile-Ife, Nigeria 6 Department of Surgery, Obafemi Awolowo University Teaching Hospitals Complex, Ile-Ife, Nigeria Abstract This study monitored the distribution of organochlorine pesticides (OCPs) in the blood serum of breast cancer patients and control subjects. Blood samples from 50 breast cancer patients and 50 controls were analyzed using Gas Chromatography-Electron Capture Detection. Thirteen OCPs, including DDT, DDE, methoxychlor, aldrin, dieldrin, endrin, endosulfan (I, II, and sulfate), heptachlor, heptachlor epoxide, γ-BHC, and δ-BHC, were detected. Endosulfan II had the highest mean concentrations (16.505 ppb in breast cancer patients and 10.625 ppb in controls), while DDE had the lowest (0.039 ppb and 0.014 ppb, respectively). A DDE/DDT ratio below 10 indicated recent DDT exposure. The significantly higher presence of DDT, aldrin, γ-BHC, and δ-BHC in breast cancer patients suggests a potential link between OCP exposure and breast cancer risk. The clustering of OCPs further indicates possible synergistic effects that may enhance cancer risk. Environmentally safer alternatives to OCPs should be adopted in agriculture and industry to reduce exposure risks. © NJEH 2025 Published by Living Science Foundation. Keywords: Breast cancer; Case-control study; DDT; Organochlorine pesticides; Serum 1. Introduction Organochlorine pesticides (OCPs) are a class of chlorinated compounds, commonly categorized as persistent organic pollutants due to their environmental persistence and high lipid solubility (Baratzhanova et al., 2024). Their extensive use in agriculture and industry has led to widespread environmental contamination (Litynska, 2024) and bioaccumulation throughout the food chain (Ansari et al., 2024). OCPs are broadly classified into three groups: dichlorodiphenylethanes, chlorinated cyclodienes, and hexachlorocyclohexanes (Kartalović et al., 2020; Zuo et al., 2023). Exposure to these chemicals has been linked to various adverse health effects, including oxidative stress, metabolic disorders, immunosuppression, and neurotoxicity (Taiwo, 2019; Chen et al., 2022; Pathak et al., 2022). Accepted 30th May, 2025. DOI: 10.5281/zenodo.15583103 ∗ Corresponding author Email address: aweyemi4u@yahoo.com (Yemisi Tosin Awe)