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Integrated Assessment of Heavy Metal Contamination in Water, Sediments, and Fish Along the Ravi River, Lahore: Pollution Indicators, Bioaccumulation, and Human Health Risks

This study evaluates heavy metal contamination in the Ravi River's water, sediments, and fish, revealing moderate to high cadmium levels and anthropogenic influence while concluding that human health risks from consuming local fish species remain within acceptable limits.

Original authors: Farooq Siddique Qazi, Muhammad Atif Irshad, Iqra Nasim, Rab Nawaz, Khawar Sultan, Suliman Mohammed Suliman Alghanem, Haifa Abdul Aziz Sakit Alhaithloul, Michel Federighi, Muhammad Tanveer Munir

Published 2026-10-23

📖 5 min read🧠 Deep dive

CC BY 4.0

Original authors: Farooq Siddique Qazi, Muhammad Atif Irshad, Iqra Nasim, Rab Nawaz, Khawar Sultan, Suliman Mohammed Suliman Alghanem, Haifa Abdul Aziz Sakit Alhaithloul, Michel Federighi, Muhammad Tanveer Munir

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Rivers are the arteries of civilization, carrying water, nutrients, and the lifeblood of economies through cities and fields. Yet, as human activity intensifies, these waterways often become repositories for the invisible byproducts of industry and urban life. Among the most persistent of these byproducts are heavy metals, elements like cadmium, chromium, and lead that do not break down or disappear. Instead, they accumulate. When these metals enter a river, they settle into the mud or dissolve into the current, where they are absorbed by the smallest organisms. Over time, these toxins move up the food chain, concentrating in the muscles of fish that people eat. The central question for scientists and public health officials is not just whether these metals are present, but whether the levels found in the environment translate into a tangible danger for the people who rely on the river for food and water.

In the bustling region surrounding Lahore, Pakistan, the Ravi River faces exactly this challenge. A recent study by researchers from the University of Lahore and international partners set out to map the extent of this contamination and, more importantly, to understand what it means for the people living along its banks. The team focused on three specific heavy metals known for their toxicity: cadmium, chromium, and lead. They examined the water itself, the sediment at the riverbed, and the flesh of two popular fish species, Labeo rohita and Cirrhinus mrigala, which are staples in local diets. By measuring the concentration of these metals in each environment, the researchers could trace how pollution moves from the water into the fish and, finally, assess the risk to human health if those fish are consumed.

The investigation covered five distinct locations along the river, stretching from the entry point near the Siphon to the Head Balloki barrage. The researchers found that the river is indeed carrying a significant load of pollution, but the severity varies dramatically depending on where you look. The water quality showed a clear pattern of contamination, with the highest levels of cadmium found at the Shahdara and Park View sites, where concentrations reached 2.13 milligrams per liter. This is a substantial amount, suggesting a heavy influx of industrial or municipal wastewater in these specific areas. Lead and chromium were also present, with chromium peaking at the Park View site. The sediment, or the mud at the bottom of the river, acted as a long-term storage tank for these pollutants. In the sediment samples, cadmium levels were particularly alarming, reaching as high as 16 milligrams per kilogram in some spots, far exceeding the natural background levels expected in a healthy river system.

When the team turned their attention to the fish, they discovered that the animals were actively absorbing these toxins from their surroundings. The muscles of the fish, the part people eat, contained measurable amounts of all three metals. The levels were not uniform; fish caught near the Park View and M2 bridges showed higher concentrations of cadmium and lead compared to those caught further upstream. For instance, cadmium levels in the fish muscles ranged from 0.14 to 0.77 milligrams per kilogram. While these numbers indicate that the fish are bioaccumulating the metals—meaning they are taking them in faster than they can get rid of them—the researchers were careful to place these findings in the context of human safety. They calculated the potential health risks for both adults and children who might eat this fish, considering typical consumption rates in Pakistan.

The results of this risk assessment offered a nuanced picture. Despite the clear presence of heavy metals in the water, sediment, and fish, the study concluded that the immediate threat to human health from eating these fish is currently low. The researchers calculated a "hazard index," a measure of non-cancer health risks, and found that for all locations and both fish species, the value remained well below the safety threshold of one. This means that for the average person eating fish from the Ravi River, the likelihood of suffering from non-cancerous health effects due to these specific metals is negligible. Similarly, the estimated risk of developing cancer over a lifetime from consuming these fish fell within an acceptable range, generally considered safe by international standards. The study did note that children face a slightly higher relative risk than adults due to their smaller body weight, but even for them, the calculated risks did not cross the line into danger.

However, the study also highlighted that this safety is precarious and localized. The contamination is not evenly distributed; it is concentrated in specific "hotspots" near urban and industrial zones. The fact that the fish are accumulating these metals proves that the river ecosystem is under stress, and the metals are moving through the food web. The researchers emphasized that while the current risk is low, the presence of these pollutants is a warning sign. If the sources of pollution—untreated sewage and industrial effluents—are not addressed, the levels could rise, potentially pushing the risk beyond safe limits in the future. The study serves as a critical baseline, confirming that while the Ravi River is polluted, the fish currently available for consumption do not yet pose a public health crisis, provided that monitoring continues and pollution sources are managed. The findings underscore the need for ongoing vigilance to ensure that the river remains a safe source of food for the communities that depend on it.

Technical Summary: Integrated Assessment of Heavy Metal Contamination in Water, Sediments, and Fish Along the Ravi River, Lahore

Problem Statement
The Ravi River, a critical lifeline for Lahore, Pakistan, faces severe pollution from untreated urban and industrial effluents, leading to the accumulation of heavy metals (HMs) such as cadmium (Cd), chromium (Cr), and lead (Pb). While previous studies have documented HM contamination in individual environmental compartments (water or sediments) or specific fish species, there is a lack of comprehensive assessments that integrate ecological bioaccumulation pathways with human health risk evaluations across the entire riverine ecosystem. The persistence of HMs, their bioaccumulation in aquatic food chains, and the subsequent potential for human exposure through fish consumption and water contact pose significant ecological and public health concerns, particularly in developing regions where regulatory monitoring may be inconsistent.

Methodology
This study employed a systematic sampling approach across five locations along the Lahore stretch of the Ravi River: Siphon, Shahdara, M2, Park View, and Head Balloki.

Sample Collection: Water, sediment, and fish samples (Labeo rohita and Cirrhinus mrigala) were collected from three distinct points per site (bank, mid-channel, and 60m from bank). Fish samples were preserved in cold chains, and epaxial muscles were dissected for analysis.
Analytical Techniques: Physicochemical parameters (pH, EC, TDS, etc.) and HM concentrations were quantified using Atomic Absorption Spectroscopy (AAS) following acid digestion protocols. Results were expressed in mg kg⁻¹ dry weight for solids and mg L⁻¹ for water.
Pollution Indices: To evaluate contamination levels, the study calculated the Geo-accumulation Index ( $I_{geo}$ ), Contamination Factor (CF), and Enrichment Factor (EF) for sediments and water, using geochemical background values and WHO guidelines.
Bioaccumulation Metrics: Bioconcentration Factors (BCF) and Bio-sediment Accumulation Factors (BSAF) were computed to determine metal transfer from water and sediments to fish tissues.
Health Risk Assessment: Human health risks were assessed via Estimated Daily Intake (EDI), Hazard Quotient (HQ), Hazard Index (HI) for non-carcinogenic risks, and Lifetime Cancer Risk (LCR) for carcinogenic risks. Calculations accounted for exposure parameters specific to adults and children, including ingestion rates and body weights.

Key Contributions

Holistic Ecosystem Assessment: The study provides an integrated view of HM distribution across water, sediment, and biota (fish muscle), linking environmental contamination directly to bioaccumulation.
Multi-Index Pollution Evaluation: By applying $I_{geo}$ , CF, and EF simultaneously, the research offers a nuanced understanding of contamination sources, distinguishing between natural geochemical variability and anthropogenic enrichment.
Species-Specific Bioaccumulation: The research details the differential accumulation of Cd, Cr, and Pb in two commercially important fish species (L. rohita and C. mrigala), highlighting variations based on location and species.
Quantitative Risk Characterization: The paper quantifies both non-carcinogenic and carcinogenic risks associated with fish consumption, utilizing standard toxicological reference doses and slope factors to provide a screening-level risk assessment for the local population.

Results

Environmental Contamination: Water quality showed neutral pH but elevated electrical conductivity at urban sites (M2, Park View). Sediment pH was alkaline.
- Cadmium (Cd): Exhibited the most severe contamination. Water Cd levels ranged from 0.13 to 2.13 mg L⁻¹, and sediment levels from 1.22 to 16 mg kg⁻¹. $I_{geo}$ , CF, and EF values indicated moderate to extreme contamination, particularly at downstream sites (Park View, Head Balloki), suggesting strong anthropogenic influence.
- Chromium (Cr) and Lead (Pb): Generally showed low-to-moderate contamination levels in sediments and water, with localized hotspots near industrial zones.
Fish Bioaccumulation:
- HM concentrations in fish muscles varied by site and species. Cd ranged from 0.14 to 0.77 mg kg⁻¹, Cr from 0.15 to 0.88 mg kg⁻¹, and Pb from 0.06 to 0.24 mg kg⁻¹.
- Bioaccumulation Factors: Cr showed the highest BCF values, ranging from 15.7 to 31.2 L kg⁻¹ across the fish species (with L. rohita reaching the maximum), indicating efficient uptake from water, while BSAF values were generally <1, suggesting limited transfer from sediments to fish, except for Pb at the M2 site where BSAF approached 1.
Human Health Risks:
- Non-Carcinogenic Risk: The Hazard Index (HI) for all sites and species remained below the safety threshold of 1 for both adults and children, even under worst-case consumption scenarios. Cd contributed the highest HQ values.
- Carcinogenic Risk: Lifetime Cancer Risk (LCR) values for Cd and Cr were generally within the acceptable range ( $10^{-6}$ to $10^{-4}$ ) for adults and negligible (< $10^{-6}$ ) for children, with the exception of Cr in C. mrigala from Head Balloki, which showed a slight jump over the one-in-a-million ( $10^{-6}$ ) threshold.

Significance and Claims
The paper concludes that while the Ravi River is significantly contaminated with heavy metals—particularly Cd due to anthropogenic inputs—the current estimated risk to human health from consuming the studied fish species remains within internationally accepted regulatory thresholds. The authors assert that the findings provide valuable baseline data for environmental monitoring and ecological risk assessment in developing regions.

The study emphasizes that despite the low immediate health risk, the presence of contamination hotspots necessitates continued monitoring, stricter regulation of industrial and municipal effluents, and targeted remediation to protect the river's ecological integrity and long-term food safety. The authors modestly frame their work as a "screening-level" study, acknowledging limitations such as the use of deterministic risk assessment, the exclusion of other heavy metals and trophic groups, and the lack of seasonal variation analysis. They suggest that future research should incorporate probabilistic risk assessments and a broader range of trace elements to refine risk management strategies.

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