Bioavailability of heavy metals in fish from Rawal lake and its health risk assessment using an in vitro digestion model

Abstract

The increasing concentration of heavy metals (HMs) in aquatic ecosystems, driven by anthropogenic activities, represents a critical threat to environmental sustainability, aquatic biodiversity and human health. To address this issue, this study assessed HM accumulation in water and six fish species from Rawal lake, Islamabad, Pakistan. Water samples showed the concentration of several HMs exceeding WHO guideline limits. Bottom-feeder fish like C. mrigal and C. carpio exhibited higher metal concentrations than surface feeders, posing increased health risks. Correlation analysis and PCA identified shared contamination sources for Zn–Ni, Cd–Pb, Al–Ni, As–Ni, and Mn–Co, whereas Cu was linked to a distinct source. Calcium had the highest bioaccessibility percentage (62.90%). Dietary exposure risks were assessed for adults and children in fisherfolk and the general population via in vitro digestion. Health risk results revealed non-carcinogenic risks for fisherfolk (HI > 1), particularly through C. mrigal, C. idella, and C. carpio, while risks for the general population remained within safe limits (HI < 1). The total carcinogenic risk exceeded the USEPA limit (>1 × 10⁻⁴) for the general population due to C. mrigal and C. carpio consumption and for fisherfolk consuming all fish species. These findings emphasize the need for strict environmental regulations and evidence-based public health interventions to mitigate HM exposure risks.