Detection, distribution, and health risk assessment of heavy metals in wild catfish sold in Maiduguri Metropolis of Borno State, Northeastern Nigeria

Heavy metals (HMs) are naturally occurring elements with high atomic weights and a density at least five times greater than water. HMs can be released into the soil, water, and air through industrial, domestic, agricultural run-offs, medical and technological activities. Thirty wild fresh catfish were bought from two major fish markets in Maiduguri (Custom and Monday markets). Zinc (Zn) and Arsenic (As) were determined by Atomic Absorption spectrophotometer. Data obtained were analyzed using descriptivestatistics and independent sample t-tests. The estimated daily intake (EDI) of the metals was calculated, and the target cancer risk (TCR), target hazard quotient (THQ), and hazard index (HI) was derived. The mean concentration (mg/Kg ± SD) of Zn in the liver (0.26 ± 0.32) was higher compared to that in muscle (0.22 ± 0.27), but this was not statistically different (t (58) = 0.608, p = 0.545). However, the mean concentration of As in the liver (0.27 ± 0.33) was lower compared to that in the muscle (0.28 ± 0.23), but this was not statistically different (t (52) = -0.003, p = 0.997). Although, no significant statistical difference, the mean concentration ranking of Zn based on the Fish market was Monday market > custom market, while that of As was custom market > Monday market. EDI values were within tolerable limits. TCR, THQ, and HI values obtained were below the threshold of 1. In conclusion, HMs (Zn and As) were detected in the liver and muscle of all fish samples tested at a lower rate compared to their Maximum Permissible Limits (MPLs) set by the World Health Organization (WHO). However, because of their non-degradable nature and tendency to bio-accumulate in fish tissues and organs, it can be concluded that long-term consumption poses a greater Public Health risk of HMs intoxications in the study area. Therefore, fish consumers should be enlightened more about the harmful effects of HM toxicity by relevant health authorities.