Occupational Carcinogen Exposure Burden and Cancer Risk Estimation Among Workers in Nigerian Heavy Industry: A Quantitative Risk Assessment Study

Quantitative occupational cancer risk estimation from carcinogen exposure in Nigerian heavy industry remains absent from the national cancer burden literature, precluding evidence-based prioritization of occupational cancer prevention resources. This doctoral study conducted a quantitative risk assessment of occupational carcinogen exposure burden and excess cancer risk among workers in heavy industrial sectors across Kano, Lagos, and Rivers States, representing North West, South West, and South South Nigeria respectively. The study enrolled 1,200 workers from cement manufacturing, petroleum refining, steel fabrication, and battery recycling industries. Priority carcinogens assessed included benzene, asbestos, crystalline silica, chromium VI, and polycyclic aromatic hydrocarbons. Exposure assessment combined personal air monitoring, biological sampling, and exposure reconstruction using mathematical models. Excess lifetime cancer risk was estimated using NIOSH and USEPA quantitative risk assessment methodologies. Findings demonstrated that excess lifetime lung cancer risk exceeded 1 per 1,000, a broadly accepted regulatory action threshold, for 38.6 percent of evaluated industrial workers. Bladder cancer risk attributable to benzene exposure exceeded action thresholds for 27.4 percent of petroleum sector workers. Aggregate occupational carcinogen burden was highest in battery recycling and asbestos-handling operations. The study delivers the first comprehensive quantitative occupational cancer risk assessment for Nigerian heavy industry, providing an original quantitative foundation for occupational carcinogen regulation reform and targeted cancer surveillance program development. Keywords: occupational cancer, carcinogen exposure, quantitative risk assessment, heavy industry, Nigeria.