Determination of Heavy Metals in Canned Fish Products Sold in Port Harcourt Markets, Rivers State

Canned fish products are widely consumed across South South Nigeria as affordable and shelf-stable protein sources, yet concerns about heavy metal contamination arising from can corrosion, processing, and raw material quality are inadequately addressed in the local food safety literature. This study determined the concentrations of lead, cadmium, tin, copper, zinc, and iron in canned fish products, specifically sardines, mackerel, and tuna, purchased from three major markets in Port Harcourt. Forty-five samples were digested using dry ashing followed by acid dissolution, and metal analysis was performed using atomic absorption spectrophotometry. Tin concentrations ranged from 18 to 187 mg/kg, with levels in eighteen samples exceeding the Codex Alimentarius maximum of 100 mg/kg for canned fish. Lead was detected in 82 percent of samples at concentrations between 0.08 and 1.2 mg/kg, with multiple samples above the EU maximum level. Cadmium was present in 60 percent of samples at levels between 0.04 and 0.31 mg/kg. Iron and zinc were within normal nutritional ranges. Copper was at acceptable levels in most samples. Older-looking cans with damaged lacquer coatings consistently showed higher tin and lead levels, suggesting internal corrosion as a contamination source. These findings indicate significant food safety risks associated with canned fish consumption in Port Harcourt and recommend stricter import quality control, labelling requirements, and consumer education about the risks associated with consuming products from damaged or bulging cans.

Keywords: heavy metals, canned fish, tin contamination, atomic absorption spectrophotometry, Port Harcourt