Evaluation of some heavy metals in Pangasius hypothalmus and Tilapia nilotica and the role of acetic acid in lowering their levels

Abstract

Concentrations of cadmium, mercury, manganese, phosphorus, lead and zinc in samples of Basa fish (Pangasius hypothalmus ) and some fresh water fish ( Tilapia nilotica , named Bolti and Karmout) collected from Kafer-El-Zayat were determined. Karmout fish contained the highest level of metals where phosphorus level was 3.45 µg/g, lead (1.51 µg/g), zinc (1.03 µg/g), cadmium (0.17 µg/g), manganese (0.08 µg/g) and mercury (0.007 µg/g). In Bolti fish, phosphorus level was 4.03 µg/g, lead (0.83 µg/g), zinc (0.62 µg/g), cadmium (0.12 µg/g), manganese (0.08 µg/g) and mercury (0.004 µg/g). In Basa fish, phosphorus level was 4.06 µg/g, lead (0.79 µg/g), zinc (0.62 µg/g), cadmium (0.12 µg/g), manganese (0.07 µg/g) and mercury (0.004 µg/g). Cadmium and lead levels in all examined fish were higher than permissible safety level of human use (0.1 ppm). Pre-treatment of fish muscles by acetic acid (5%) for a period of 15 min resulted in marked reduction of metals in these fish. When the Basa fish was immersed in 5% acetic acid, the cadmium level in the flesh was reduced from 0.12 to 0.07 µg/g (41.6%) and lead level was reduced from 0.83 to 0.41 µg/g (51.9%). In Bolti fish, pre-treatment of the fleshy parts by acetic acid reduced cadmium level from 0.12 to 0.07 µg/g (58.3%) and lead was reduced from 0.83 to 0.02 µg/g (24%). The same result was observed in Karmout fish, where pre-treatment with acetic acid lowered the cadmium level from 0.17 to 0.05 µg/g (29.4%) and lead was lowered from 1.51 to 0.82 µg/g (54.3%).