Heavy Metal Pollution of Fish And Fish Oils From Some Coastal And Inland Waters of Ghana

ABSTRACT

While fish and fish oil promote good health, increasing environmental pollution may introduce heavy metals into the fish which may render them injurious to health. Nine commonly consumed fish samples in Ghana, five from marine sources and four from freshwater sources were analysed for their heavy metal contents. The heavy metals are Cadmium (Cd), Lead (Pb), Mercury (Hg), Arsenic (As) and Selenium (Se). The fish samples are Herring (Sardinella species), Redfish (Red mullet), Mackerel species, Tuna species and Anchovies all from coastal waters and Tilapia (Oreochromis niloticus'). Blolo (Chrvsichthvs nigrodiaitatus). Catfish (Heteroblancus species) and One- mouth- thousand (Serrathrissa leonensis) from fresh waters. Oil extracted from four fish samples were also analysed for their heavy metal contents. The fishes were selected from four environmental zones designated heavy industrial (James Town - Accra and Tema), light industrial (Apam and Elmina), river/lake (Weija and Kpong) and mining environment (Obuasi and Dunkwa). For each environmental zone, two locations were chosen based on industrial and/or fishing activities in the area. The analysis was done on the head, bone, flesh, whole fish and scales for those who have it in order to ascertain the distribution of the metal in the fish body. The metal contents were analysed with Atomic Absorption Spectrophotometer (AAS) Generally the bone had the highest content of the heavy metals. It was followed by the head, the scale, and then the flesh. The total metal levels in the whole fish was higher than that in the flesh alone. Analysis of variance showed significant difference (p= 0.03) in the levels of each heavy metal in the fish parts. There was a significant correlation (r=0.67 and p=0.01), between the Cadmium levels in the flesh and bone. The rest of the metals did not show any significant correlation in their distribution in the flesh and the bone. Mercury levels occurred as the highest heavy metal in all parts of the fish followed by Arsenic and Lead whose levels were close. Cadmium levels were lowest in the fish tissues studied. The ranges of the metal in the body of all the fish samples are as follows; Mercury 25 - 300ug/g dried weight of fish, Lead 2.44 36.6ug/g, Arsenic 3.26 - 36.96ug/g and Cadmium 0.3 2.8ug/g. Selenium analysed in some of the fishes had levels slightly higher than Arsenic and lead in the flesh. Selenium levels ranged between 8.0 - 70 ug/g.