Contamination features, geo-accumulation, enrichments and human health risks of toxic heavy metal(loids) from fish consumption collected along Swat river, Pakistan

Toxic heavy metal(loids) (THMs) are released into natural water systems from geological and anthropogenic sources, and easily accumulated via water and sediments in aquatic fish species. The monitoring of THM concentrations in river water, sediments and fish muscles is therefore, essential to make sure acquiescence with food security guidelines and resulting end user safety. The present study aimed to investigate the concentrations of arsenic (As), cadmium (Cd), lead (Pb), chromium (Cr), copper (Cu), nickel (Ni) and zinc (Zn) in water, bed sediments and their bioaccumulation in freshwater fish tissues collected from five locations along Swat River, Pakistan. Results indicated that Cd concentration in the downstream (30%) water samples exceeded the safety guideline values of World Health Organization (WHO), while the other selected THMs were within the safety limits. The ecological risk (E_ri) for sediments showed considerable ecological risk (80≤Eri<160) to excessive ecological risk (E_ri>320) for Pb, As and Cd, while the potential ecological risk (RI) showed considerable level ((190≤RI<380) of risk at downstream. Moreover, downstream portion showed multifold potential ecological risk index enrichment as compared to upstream portion of the river. Likewise in fish tissues the THMs were found in order of Zn >Cd >Pb >Cr >As >Cu >Ni. In the study area, the selected THMs were within the permissible limits all the fish tissue samples showing no potential health risk (carcinogenic and non-carcinogenic <1) for the local inhabitants and fishermen. But in near future due to the continuous flow of wastewater from (industrial, agriculture and hotels) without treatment and open dumping and throwing of municipal wastes directly into the river as it passes through downstream may deteriorate river ecosystem. As a whole the downstream of the river was more polluted as compared to the upstream. So appropriate implementation of management policies beside THMs contamination their accumulation in freshwater ecologies and management of aquatic life should be the prime priorities of the state worldwide to protect fragile environment.