Assessment of Heavy Metal Concentration in Some Selected Welding Sites (Case Study: Northern Cross River State)

Dose (mg/kg/day) Cancer Slope Factor (SF) Cd 0.001 6.1 Cr 0.003 0.5 (Cr VI proxy) Pb 0.0035 Not officially assigned (screening usage varies) Ni 0.02 0.84 Cu 0.04 Non-carcinogenic dominant Co 0.02 Limited carcinogenic data Fe 0.7 Essential element (non-carcinogenic) (Source: USEPA Risk Assessment Guidance, WHO, Alloway 2013) Hazard Quotient (HQ)and Carcinogenic Risk (CR) Table 4.3 Hazard Quotient (HQ) and Carcinogenic Risk (CR) Metal Mean Concentration (mg/kg) Hazard Quotient (HQ) Carcinogenic Risk Indicator (CR) Cadmium (Cd) 1.34 1,340.00 8.174 Chromium (Cr) 257.0 85,666.67 128.500 Lead (Pb) 47.0 13,428.57 Not Applicable Copper (Cu) 123.0 3,075.00 Not Applicable Iron (Fe) 1674.0 2,391.43 Not Applicable Cobalt (Co) 0.003 0.15 Not Applicable Nickel (Ni) 6.72 336.00 5.645 , Hazard Index (HI) The computed Hazard Index (HI) for combined heavy metal exposure is: 106,237.82. The Hazard Quotient results indicate that chromium represents the dominant non-carcinogenic risk contributor, exhibiting HQ values several orders of magnitude above acceptable safety limits. Cadmium and lead further contribute substantially to potential health risks due to their low reference doses and cumulative toxicity. The Hazard Index greatly exceeds unity, implying the possibility of adverse health effects under chronic exposure scenarios. Carcinogenic risk screening identifies chromium as the principal cancer-related concern, with additional contributions from cadmium and nickel. Result discussion • Chromium Dominant Carcinogenic Risk Contributor is seen Cr. Chromium contamination represents the most critical health concern. Hexavalent chromium (Cr VI) is recognized as; highly carcinogenic, genotoxic and capable of inducing DNA damage (WHO, 2007). Given the extreme Cr enrichment observed, the probability of carcinogenic risk increases significantly, especially among welders exposed to metal fumes and dust (Antonini, 2003). • Cadmium Chronic toxicity and cancer risk cadmium exposure has been linked with Kidney damage, skeletal disorders and increased cancer risk (Jarup, 2003; WHO, 2007). Nickel (Ni): Carcinogenic Potential • Nickel Ni compounds are associated with respiratory toxicity and potential carcinogenicity, reinforcing long-term exposure concerns (WHO, 2007). • Lead Neuro-developmental Hazard is associated with high Pb exposure, lead is a cumulative toxicant capable of inducing; cognitive impairment, neurological dysfunction and developmental disorders (Jarup, 2003). Carcinogenic Risk Perspective Carcinogenic risk increases proportionally with: metal concentration, exposure frequency, toxic potency (Slope Factor) (USEPA, 1989). Given the concentration patterns observed: • Chromium = Highest cancer concern • Cadmium = Severe chronic toxicity risk • Nickel = Significant carcinogenic relevance The study therefore suggests potential lifetime carcinogenic risks for exposed populations. Conclusion This study conclusively demonstrates that welding activities constitute a significant source of heavy metal contamination in soils within Northern Cross River State. The results provide strong geochemical and statistical evidence that anthropogenic inputs from welding operations have substantially elevated metal concentrations beyond natural background levels. Among the analyzed metals, chromium represents the most critical contaminant due to its extreme , concentration levels, high contamination factor, and well-documented toxicity. The dominance of chromium contamination signifies a serious environmental concern, as prolonged accumulation may result in irreversible soil quality deterioration and ecological imbalance. The integration of contamination indices (CF, PLI, Igeo) confirms that soils surrounding welding sites are severely polluted, with contamination patterns clearly attributable to human activities rather than natural geological processes. The elevated Pollution Load Index values further emphasize the cumulative nature of metal deposition across locations. Importantly, the study highlights that even metals naturally present in soils, such as iron, can reach abnormally high enrichment levels under sustained industrial influence. This underscores the need to distinguish between lithogenic presence and anthropogenic amplification. From an environmental health perspective, the findings raise significant concerns. The persistent accumulation of toxic metals, particularly chromium, may pose long-term risks through bioaccumulation, mobility, and human exposure pathways. Without intervention, continued welding activities may exacerbate contamination trends and associated health implications. In conclusion, welding-related anthropogenic activities are a dominant driver of heavy metal pollution in the study area, necessitating urgent environmental management and regulatory attention. Recommendations Based on the findings of this study, the following recommendations are proposed to mitigate heavy metal contamination and reduce associated environmental and health risks: • Environmental Monitoring & Regulation Regulatory agencies and environmental protection authorities should establish routine monitoring programs around welding clusters and automobile workshops. Continuous assessment of soil quality is necessary to detect early contamination trends and prevent long- term ecological damage. Strict enforcement of environmental safety guidelines should be implemented to control indiscriminate disposal of metal scraps, slag residues, spent electrodes, and other welding wastes that contribute to metal accumulation. • Waste Management Practices Welding workshops should adopt proper waste handling and disposal systems. Metal residues, filings, and electrode wastes must be collected and managed using environmentally safe methods rather than being released directly onto surrounding soils. The introduction of centralized waste collection points within industrial clusters would significantly reduce diffuse contamination. • Occupational Health & Safety Measures Given the elevated concentrations of toxic metals, particularly chromium, welders should be mandated to use personal protective equipment including: protective gloves, respiratory masks and Safety clothing. Training programs should be conducted to educate artisans on the health implications of chronic metal exposure and safe operational practices. • Site Management & Remediation Highly contaminated locations should be considered for soil remediation strategies, such as: Phytoremediation using metal-tolerant plants and soil replacement or stabilization techniques. , Preventive land management policies should be encouraged to minimize continuous contaminant build-up. • Public Health Awareness Community-level awareness programs should be initiated to inform residents near welding sites about potential exposure pathways, especially for children who may be more vulnerable to heavy metal toxicity. • Policy & Urban Planning Considerations Urban development policies should regulate the location and clustering of welding workshops, ensuring safe distances from residential zones, schools, and agricultural lands. , References Abdullahi, S., & Musa, M. S. (2023). Health risk assessment of some heavy metals in soil samples around identified metal workshops. FUDMA Journal of Sciences, 7(2), 240– 245. Adamu, A. B., Patiko, H. M., Abdullahi, A. M. Y., & Hassan, G. S. (2022). Hazard evaluation of welding and fabrication workshops in Minna Metropolis, Nigeria. Iconic Research and Engineering Journals , 3(6), 29–33. Alloway, B. J. (2013). Heavy metals in soils (3rd ed.). Springer. Antonini, J. M. (2003). Health effects of welding. Critical Reviews in Toxicology, 33(1), 61– 103. Edu, E. A., &Akwaji, P. I. (2017). Pentaclethra macrophylla Benth and Parkia biglobosa Jacq: The declining giants of the rainforest of Nigeria. World Scientific News, 64, 127–138. Eka, F. A., Yoki, Y., Puji, L., Khatarina, O., &Muhayatun, S. (2024). Characteristics of air exposure in welding workshop workers. E3S Web of Conferences. https://doi.org/10.1051/e3sconf/202448507002. Hakanson, L. (1980). An ecological risk index for aquatic pollution control. Journal of Water Research, 14, 975–1001. International Agency for Research on Cancer . (2012). Monographs on the evaluation of carcinogenic risks to humans. IARC. Järup, L. (2003). Hazards of heavy metal contamination. British Medical Bulletin, 68(1), 167– 182. Kabata-Pendias, A. (2011). Trace elements in soils and plants (4th ed.). CRC Press. Kabata-Pendias, A., & Mukherjee, A. B. (2007). Trace elements from soil to human. Springer. Kouakou A R., Benjamin Y., Albert T., Adouby K (2016). Assessment of Heavy Metals Contamination in Sediments of the Vridi Canal (Côte d’Ivoire). Journal of Geoscience and Environment Protection, 4 (10). Nwachukwu, M. A., Feng, H., &Alinnor, J. (2010). Trace metal deposition in soil from auto- mechanic activities. Journal of Environmental Monitoring and Assessment, 161, 385– 397. Nwachukwu, M. A., Feng, H., &Alinnor, J. (2010). Statistical evaluation of environmental contamination studies. (Retained based on body usage-verify if separate citation needed.) Occupational Safety and Health Administration . (2003). Welding fumes and heavy metals. Oketayo, O. O., Suaib, O., Peter, O. I., Oluwatosin, O., & Joel, O. (2024). Assessment of some heavy metals in soil samples around identified metal workshops. Journal of Water and Environmental Sustainability , 4(2), 28–39. Skoog, D. A., Holler, F. J., & Crouch, S. R. (2018). Principles of instrumental analysis (6th ed.). Cengage Learning. Sparks, D. L. (2003). Environmental soil chemistry. Academic Press. Stern, R. M. (1981). Health effects for welders. Journal of Environmental Health Perspectives, 41, 235–253. Taylor, J. K. (1987). Quality assurance of chemical measurements. CRC Press. World Health Organization . (2007). Evaluation of certain food additives and contaminants. WHO. , World Health Organization . (2010). Exposure to lead: A major public health concern. WHO. Wuana, R. A., &Okieimen, F. E. (2011). Heavy metals in contaminated soils: A review. ISRN Ecology. , APPEDIX I CONCENTRATION CHART FOR ALL METALS ,