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

Report on the Integrated Risk Assessment of Tannery Effluents in Naraguta, Nigeria

Executive Summary

This report presents a comprehensive evaluation of the environmental and public health impacts of untreated tannery wastewater in Naraguta, Jos, Nigeria, with a significant focus on its implications for the United Nations Sustainable Development Goals (SDGs). An analysis of 84 surface water samples collected over one year revealed severe contamination, directly undermining progress toward several key SDGs. Pollutant levels, including heavy metals (chromium), organic matter (BOD, COD), and microbial pathogens (E. coli, helminth eggs), far exceeded permissible limits set by national (NESREA) and international (WHO) standards. The study utilized a multi-index approach (Pollution Index, Geo-Accumulation Index, Environmental Hazard Index, Health Risk Index) to quantify the risks. Findings indicate that current industrial practices severely compromise SDG 6 (Clean Water and Sanitation) by degrading water quality and threaten SDG 3 (Good Health and Well-being) through exposure to toxic and pathogenic contaminants. The high pollution load also negatively impacts SDG 14 (Life Below Water) and SDG 15 (Life on Land) by disrupting local ecosystems. The report concludes with an urgent call for policy interventions aligned with SDG 12 (Responsible Consumption and Production), advocating for stricter effluent controls, investment in modern wastewater treatment, and continuous monitoring to foster sustainable industrial development that protects both human and ecological health.

1.0 Introduction: Industrial Activity and the Sustainable Development Agenda

The global tanning industry is a significant economic contributor, aligning with SDG 8 (Decent Work and Economic Growth) by providing employment and raw materials. However, in developing nations like Nigeria, these economic benefits often come at a severe environmental and social cost. The discharge of untreated tannery effluents poses a direct challenge to the 2030 Agenda for Sustainable Development. This report assesses the situation in Naraguta, where industrial wastewater discharge creates a critical conflict between economic objectives and fundamental environmental and health goals.

• SDG 6 (Clean Water and Sanitation): Untreated effluents containing heavy metals, organic pollutants, and microbial contaminants directly pollute surface water, rendering it unsafe for human consumption and domestic use.
• SDG 3 (Good Health and Well-being): Communities relying on these contaminated water sources face significant health risks, including waterborne diseases and chronic toxicity from chemical exposure.
• SDG 12 (Responsible Consumption and Production): The lack of wastewater treatment facilities reflects unsustainable production patterns that externalize environmental costs onto communities and ecosystems.
• SDG 14 (Life Below Water) & SDG 15 (Life on Land): The chemical and biological pollutants degrade aquatic habitats, cause biodiversity loss, and contaminate soil through irrigation, undermining ecosystem integrity.

This study provides a data-driven framework to evaluate the extent of this conflict and offers policy-oriented recommendations to align the local tanning industry with sustainable practices.

2.0 Methodology for SDG-Focused Assessment

A comprehensive, multi-index methodology was employed to quantify the environmental and health risks, providing measurable indicators relevant to SDG targets.

2.1 Sampling and Analysis

A systematic sampling strategy was implemented to assess pollution gradients and temporal variations.

1. Sample Collection: 84 surface water samples were collected monthly over one year from seven geo-referenced stations downstream from the tannery discharge point.
2. Parameter Analysis: Samples were analyzed for a wide range of pollutants according to APHA and WHO standards to ensure data reliability.
   • Physicochemical Parameters: pH, Electrical Conductivity (EC), Total Suspended Solids (TSS), Total Dissolved Solids (TDS), Biochemical Oxygen Demand (BOD), and Chemical Oxygen Demand (COD).
   • Heavy Metals: Iron (Fe) and Chromium (Cr).
   • Nutrients: Nitrate, Sulfate, Chloride, and Total Nitrogen.
   • Microbial Pathogens: Escherichia coli and helminth eggs (Ascaris lumbricoides, Hookworm, Trichuris trichiura, Strongyloides stercoralis).

2.2 Pollution and Risk Assessment Indices

Established indices were used to translate raw data into actionable insights regarding environmental degradation and public health, directly linking findings to SDG targets.

• Pollution Load Index (PLI) and Contamination Index (CI): To assess the overall pollution burden and identify hotspots, crucial for monitoring progress on SDG 6.
• Geo-Accumulation Index (I_geo): To distinguish anthropogenic pollution from natural background levels, providing evidence of unsustainable industrial practices under SDG 12.
• Environmental Hazard Index (EHI): To evaluate the ecological risk to aquatic life, informing efforts to protect biodiversity as per SDG 14.
• Health Risk Index (HRI): To quantify the chronic health risks to the local population from ingestion of contaminated water, a direct measure of threats to SDG 3.
• Principal Component Analysis (PCA): To identify the primary sources of pollution, enabling targeted interventions.

3.0 Results and Analysis in the Context of SDGs

The analysis revealed severe pollution levels that represent a significant impediment to achieving multiple Sustainable Development Goals.

3.1 Degradation of Water Quality (SDG 6)

The physical and chemical characteristics of the effluent demonstrated a profound failure to manage industrial wastewater, directly contravening the objectives of SDG 6.

• High Organic Load: Biochemical Oxygen Demand (BOD) values (210–300 mg/L) and Chemical Oxygen Demand (COD) values (570–720 mg/L) were drastically above NESREA limits, indicating severe organic pollution that depletes oxygen in water bodies, harming aquatic life (SDG 14).
• Heavy Metal Contamination: Chromium (Cr) concentrations (2.8–3.4 mg/L) were alarmingly high, exceeding the NESREA limit of 0.5 mg/L. The Geo-Accumulation Index (I_geo) for chromium reached 5.06, indicating “very strong pollution” from anthropogenic sources.
• Physical Pollution: Turbidity levels (61–155 NTU) were far above the 5–10 NTU standard, reducing water clarity and disrupting aquatic ecosystems.

3.2 Public Health Crises and Threats to Well-being (SDG 3)

The presence of chemical toxins and pathogens poses a direct and immediate threat to human health, undermining SDG 3.

• Microbial and Parasitic Contamination: The detection of E. coli (up to 23 MPN/100 mL) and various helminth eggs (up to 23 eggs/L) points to a high risk of waterborne diseases like cholera, typhoid, and parasitic infections. This fails the “zero tolerance” standard for such pathogens in water intended for domestic use.
• Chronic Health Risks from Heavy Metals: The Health Risk Index (HRI) for chromium exposure was exceptionally high, particularly for children (up to 75.56), indicating a significant risk of long-term health effects, including cancer and organ damage. The Chronic Daily Intake (CDI) for chromium was over 60 times the safe limit for children.

3.3 Unsustainable Production and Ecosystem Damage (SDG 12, 14, 15)

The findings provide clear evidence of irresponsible production patterns that degrade the environment, in opposition to the principles of SDG 12.

• Source Identification: Principal Component Analysis (PCA) confirmed that 85.9% of the pollution variance originated from industrial (anthropogenic) and microbial sources, directly linking the environmental damage to the tannery’s operational failures.
• Ecological Impact: The high Environmental Hazard Index (EHI) values for chromium, BOD, and sulphate signify severe chemical toxicity and ecological stress, threatening the survival of aquatic organisms (SDG 14) and contaminating land resources (SDG 15).

4.0 Conclusion and Recommendations for Sustainable Action

The untreated discharge of tannery effluent in Naraguta represents a critical failure in environmental management and poses a significant barrier to achieving the Sustainable Development Goals. The synergistic risks from chemical and biological contaminants threaten public health, degrade water resources, and destroy local ecosystems. To address this, an integrated approach grounded in the principles of sustainable development is imperative.

4.1 Policy and Regulatory Enforcement

1. Strengthen Enforcement: Implement strict, consistent enforcement of NESREA effluent standards to ensure compliance, directly supporting SDG 6 and SDG 12.
2. Continuous Monitoring: Establish real-time environmental monitoring programs to track pollution levels and provide early warnings, enabling evidence-based policymaking.

4.2 Investment in Sustainable Technologies

1. Modernize Wastewater Treatment: Mandate and support investment in effective wastewater treatment technologies, such as bioremediation, constructed wetlands, and advanced oxidation processes.
2. Promote Circular Economy Principles (SDG 12): Encourage the adoption of technologies for resource recovery (e.g., chromium recycling) and the reuse of treated wastewater for agricultural purposes. This approach minimizes waste and creates economic value while protecting the environment.
3. Adopt Cleaner Production: Foster partnerships between industry, academia, and government to promote the adoption of cleaner production techniques and zero-liquid discharge (ZLD) systems.

By implementing these recommendations, Nigeria can transition its tanning industry from a source of pollution into a model of sustainable industrial development that contributes positively to SDG 3, SDG 6, SDG 8, SDG 12, SDG 14, and SDG 15.

Analysis of Sustainable Development Goals (SDGs) in the Article

1. Which SDGs are addressed or connected to the issues highlighted in the article?

1. SDG 3: Good Health and Well-being

   • The article directly connects the pollution from tannery effluents to significant public health risks. It mentions that pollutants “threaten… public health” and that exposure can lead to “waterborne diseases, organ impairment, developmental abnormalities, and cancer.” The study employs a Health Risk Index (HRI) specifically to evaluate “possible health effects, particularly chronic risks to adults through ingestion exposure,” linking the chemical and biological contamination directly to human health outcomes.

2. SDG 6: Clean Water and Sanitation

   • This is the most central SDG in the article. The entire study revolves around the pollution of surface water by untreated tannery wastewater. It details the degradation of water quality through a comprehensive analysis of physicochemical, heavy metal, and microbial pollutants. The article highlights the “release of untreated wastewater from tannery industries… has resulted in serious water pollution and ecological degradation,” which directly addresses the core mission of SDG 6.

3. SDG 12: Responsible Consumption and Production

   • The article critiques the industrial practices of the tannery sector, pointing to “ineffective tannery waste management” and the lack of “adequate wastewater treatment facilities.” It calls for “stricter effluent discharge controls” and “investment in modern wastewater treatment systems.” This focus on the environmental impact of industrial production and the need for sustainable waste management aligns perfectly with the goal of achieving environmentally sound management of chemicals and wastes.

4. SDG 14: Life Below Water

   • The article describes how untreated effluents “severely degrade aquatic ecosystems by elevating BOD, COD, and toxic metal concentration, contributing to oxygen deficiency, loss of biodiversity, and eutrophication.” Although the study focuses on a river, this land-based pollution directly impacts freshwater ecosystems, which are intrinsically linked to larger marine environments. The mention of nutrient pollution (nitrate, total nitrogen) and its consequences addresses the reduction of pollution affecting aquatic life.

2. What specific targets under those SDGs can be identified based on the article’s content?

1. SDG 3: Good Health and Well-being

   • Target 3.9: By 2030, substantially reduce the number of deaths and illnesses from hazardous chemicals and air, water and soil pollution and contamination.
     
     Explanation: The article’s core purpose is to assess the “associated health risks resulting from untreated tannery wastewater.” It identifies hazardous chemicals like chromium and iron, and biological pathogens such as E. coli and helminth eggs, directly linking their presence in the water to potential illnesses in the local population. The calculation of the Health Risk Index (HRI) is a direct attempt to quantify the risk of illness from this contamination.

2. SDG 6: Clean Water and Sanitation

   • Target 6.3: By 2030, improve water quality by reducing pollution, eliminating dumping and minimizing release of hazardous chemicals and materials, halving the proportion of untreated wastewater and substantially increasing recycling and safe reuse globally.
     
     Explanation: The study provides extensive evidence of water quality degradation due to the discharge of untreated wastewater containing hazardous chemicals (chromium) and high levels of organic pollutants (BOD, COD). The conclusion explicitly calls for “implementation of stricter effluent discharge controls” and “investment in modern wastewater treatment systems,” which are direct actions needed to achieve this target.
   • Target 6.6: By 2020, protect and restore water-related ecosystems, including mountains, forests, wetlands, rivers, aquifers and lakes.
     
     Explanation: The article documents the negative impact on the aquatic ecosystem of the River Dalimi, noting that the pollution leads to “biodiversity loss, depletion of oxygen, and chronic toxicity.” This demonstrates a failure to protect a water-related ecosystem and underscores the need for restoration efforts, which is the focus of this target.

3. SDG 12: Responsible Consumption and Production

   • Target 12.4: By 2020, achieve the environmentally sound management of chemicals and all wastes throughout their life cycle… and significantly reduce their release to air, water and soil in order to minimize their adverse impacts on human health and the environment.
     
     Explanation: The study is a case study of the failure to achieve this target. The tannery’s discharge of effluents containing a “diverse blend of chemical, physical, and biological pollutants” into the river is a clear example of unsound waste management. The research calls for immediate action to control the release of these pollutants to mitigate their impact on the environment and public health.

4. SDG 14: Life Below Water

   • Target 14.1: By 2025, prevent and significantly reduce marine pollution of all kinds, in particular from land-based activities, including marine debris and nutrient pollution.
     
     Explanation: The tannery is a land-based source of pollution that contaminates the River Dalimi. The article specifically measures nutrient pollutants like “nitrate, sulfate… and total nitrogen,” which are known to cause eutrophication in aquatic systems. This land-based pollution of a river system is the primary pathway for contaminants to reach larger water bodies and eventually the ocean.

3. Are there any indicators mentioned or implied in the article that can be used to measure progress towards the identified targets?

• Physicochemical Water Quality Parameters: The article explicitly measures pH, electrical conductivity (EC), total suspended solids (TSS), total dissolved solids (TDS), Biochemical Oxygen Demand (BOD5), and Chemical Oxygen Demand (COD). These are direct indicators for assessing water quality (Target 6.3).
• Concentration of Hazardous Chemicals: The measurement of heavy metals like iron (Fe) and chromium (Cr) serves as a key indicator for pollution from hazardous chemicals (Targets 3.9, 6.3, and 12.4). The article notes chromium levels were “significantly higher than the permissible 0.5 mg/L NESREA limit.”
• Concentration of Nutrients: The analysis of nitrate, sulfate, and total nitrogen provides indicators for nutrient pollution, which is relevant to the health of aquatic ecosystems (Target 14.1).
• Microbial and Biological Contamination Levels: The quantification of Escherichia coli (in MPN/100 mL) and helminth eggs (in eggs/L) are direct indicators of biological contamination and the associated risk to human health from unsafe water (Targets 3.9 and 6.3).
• Composite Pollution Indices: The study calculates several indices that serve as comprehensive indicators. These include:
  • Pollution Load Index (PLI), Contamination Index (CI), and Geo-Accumulation Index (I_geo): These are used to quantify the overall pollution burden and anthropogenic impact, serving as indicators for the effectiveness of waste management (Target 12.4) and water quality (Target 6.3).
  • Environmental Hazard Index (EHI): This index was calculated to “analyze the potential environmental risk from these pollutants,” making it an indicator for assessing impacts on ecosystems (Targets 6.6 and 14.1).
• Health Risk Assessment Metrics: The article uses the Health Risk Index (HRI), Chronic Daily Intake (CDI), and Reference Dose (RfD) models. These metrics are used to translate pollutant concentrations into a direct measure of potential harm to human health, serving as powerful indicators for Target 3.9.

4. Summary Table of SDGs, Targets, and Indicators

Source: nature.com