Heavy metal contamination (PB, CD, AS, CR) in NPK 17-17-17 fertilizers marketed in Kinshasa, Democratic Republic of the Congo: regulatory compliance, health and environmental risk assessment

Abstract

Background: The intensification of urban and peri-urban agriculture in Kinshasa, driven by the food demands of a rapidly growing population, has led to massive use of chemical fertilizers, particularly NPK 17-17-17, valued for its balanced nitrogen, phosphorus, and potassium content. However, these fertilizers, often imported without rigorous quality control, raise concerns about the presence of heavy metals (Pb, Cd, As, Cr) and their potential risks to human health and the environment through bioaccumulation and trophic transfer.

Objective: This study aims to quantify heavy metal concentrations in NPK 17-17-17 fertilizers marketed in Kinshasa and assess their compliance with international standards (FAO, EU, ECOWAS).

Methods: Four types of NPK 17-17-17 fertilizers from different origins were sampled from five sales points in the communes of Lemba, Limete, Masina, Ngaba, and Matete. Samples were digested using HNO₃/H₂O₂ with microwave assistance and analyzed by atomic absorption spectrometry (AAS) with graphite furnace and hydride generation. Statistical analyses included descriptive statistics, ANOVA, Tukey's test, and hazard quotient (HQ) calculation.

Results: All analyzed samples showed heavy metal concentrations well below international thresholds: Cadmium from 0.00 to 0.20 mg/kg (FAO limit: 20 mg/kg), Lead from 0.00 to 0.75 mg/kg (FAO limit: 100 mg/kg), Arsenic from 0.00 to 0.30 mg/kg (FAO limit: 50 mg/kg), and Chromium from 0.00 to 0.20 mg/kg (FAO limit: 100 mg/kg). pH ranged from 4.10 to 7.50 and moisture from 1.12% to 3.82%. Significant differences were observed among origins (p < 0.05), with Sample A showing the highest concentrations. All hazard quotients (HQ) were < 1, indicating acceptable risk levels.

Conclusion: NPK 17-17-17 fertilizers currently marketed in Kinshasa comply with international heavy metal standards. However, the variability among origins and the absence of systematic quality control justify continuous monitoring to prevent any future risk of food chain contamination. Implications for CBRN risk mitigation are discussed.

Keywords: Heavy metals, NPK fertilizers, Kinshasa, Risk assessment, Food safety, Environmental contamination, Regulatory compliance.

Received Date: June 19, 2026

Accepted Date: July 10, 2026

Published Date: August 01, 2026

Available Online at: https://www.ijsrisjournal.com/index.php/ojsfiles/article/view/916