Physiological Mechanisms of Occupational Lead Toxicity and Haemopoietic System Disruption in Battery Manufacturing Workers in Lagos: A Longitudinal Mechanistic Study

Occupational lead exposure in battery manufacturing disrupts haemopoiesis through multiple converging mechanisms including aminolaevulinic acid dehydratase inhibition, iron metabolism interference, and erythrocyte membrane damage, yet no longitudinal mechanistic study has characterised these pathways in Nigerian industrial workers. This study investigated the physiological mechanisms of lead-induced haemopoietic disruption in battery manufacturing workers in Lagos, South West Nigeria, across an eighteen-month longitudinal period. An occupational cohort of 60 battery plant workers and 30 unexposed administrative controls were assessed at baseline, nine months, and eighteen months. Blood lead levels were measured by graphite furnace atomic absorption spectrophotometry. Haemopoietic mechanistic markers included aminolaevulinic acid dehydratase activity, serum iron, transferrin saturation, serum erythropoietin, erythrocyte osmotic fragility, and mean corpuscular haemoglobin concentration. Full blood count and reticulocyte count provided functional haematological endpoints. Longitudinal mixed-effects modelling and mediation analyses were applied. Results showed progressive blood lead elevation across assessment points, accompanied by declining aminolaevulinic acid dehydratase activity and rising erythrocyte osmotic fragility. Haemoglobin declined significantly at eighteen months in workers. Erythropoietin compensatorily elevated but was insufficient to prevent anaemia development. Aminolaevulinic acid dehydratase inhibition most strongly mediated lead-haemoglobin relationships. This study provides mechanistic longitudinal evidence for lead haematotoxicity pathways in Nigerian workers, a previously uncharacterised population. Mandatory blood lead monitoring, chelation thresholds, and dust control engineering are recommended. Keywords: lead toxicity, haemopoiesis, battery workers, aminolaevulinic acid dehydratase, Lagos.