Integrated Risk Assessment of Tannery Effluents using Multivariate Pollution Indices and Health Metrics in Naraguta,...

Tannery effluents contain a diverse blend of chemical, physical, and biological pollutants that threaten environmental quality and public health. This study offers a comprehensive evaluation of pollution profile and associated health risks resulting from untreated tannery wastewater discharges in Naraguta area of Jos, Nigeria. A total of 84 surface water samples were collected over a course of one year. Samples were examined for major physicochemical parameters (like pH, electrical conductivity, total suspended solids, total dissolved solids, total solids, Biochemical Oxygen Demand BOD₅, and Chemical Oxygen Demand COD) according to American Public Health Association (APHA) and World Health Organization (WHO) methods. Heavy metals (iron and chromium) were also measured using atomic absorption spectrophotometry (AAS), while levels of nutrients (nitrate, sulfate, chloride, and total nitrogen) were analyzed through spectrophotometric and titrimetric methods. Microbial pathogens such as Escherichia coli and helminth eggs (Ascaris lumbricoides, Hookworm, Trichuris trichiura, and Strongyloides stercoralis) were detected through multiple-tube fermentation and parasitological concentration methods. Pollution was quantified using established indices, including Geo-Accumulation Index (I_geo), Environmental Hazard Index (EHI), and Pollution Load Index (PLI), using National Environmental Standards and Regulations Enforcement Agency (NESREA) and World Health Organization (WHO) guideline values serving as reference standards. Pollution Index (PI) values were 3-6 times over permissible levels. Contamination Index (CI) rated samples taken from stations downstream were highly polluted based on the cumulative impacts of several contaminants. Geo-Accumulation Index (I_geo), for chromium was as high as 5.06, reflecting "very strong pollution," while I_geo, for turbidity (3.3) and colour (3.6) reflected a significant anthropogenic contribution. Health hazards were measured by the Health Risk Index (HRI) model, which included Chronic Daily Intake (CDI) and Reference Dose (RfD) models to predict ingestion-based pathways of exposure. Principal Component Analysis (PCA) revealed three principal components that accounted for 85.9% of the total variance, indicating both industrial (anthropogenic) and microbial origins of contamination. These results emphasize the pressing ecological and public health risks posed by ineffective tannery waste management. The study calls for an immediate implementation of stricter effluent discharge controls, investment in modern wastewater treatment systems, and establishment of continuous environmental monitoring programs to prevent long-term exposure and degradation.