Postharvest/Biochemistry Unit H HARRY OKYERE

LEVELS OF MERCURY, LEAD AND CADMIUM IN CANNED FISH MARKETED IN GHANA

Research Objectives The objectives of this research were to: Determine the levels of  Mercury (Hg)  Cadmium (Cd) and  Lead (Pb) in Canned Fish on the Ghanaian Market, and Compare levels with those recommended by W.H.O

INTRODUCTION Heavy metals are considered the most important form of pollution of the aquatic environment because of their  toxicity and accumulation by marine organisms  persistence and not easily biodegradable.

INTRODUCTION Sources of Heavy Metals in the Environment Mining Plumbing Laboratories Municipal wastes Combustors in industries Metal Plating Agricultural activities Commercial and industrial boilers

INTRODUCTION Canned foods especially canned fishes in particular are well eaten in the developed and developing countries because it is  convenient  affordable for most working families.

INTRODUCTION Canned fish products manufactured either locally or imported are available in supermarkets and retail shops. However owing to the great consumption of this product the safety issues related to the possibility of heavy metal contamination are of concern.

SOURCES OF CONTAMINATION OF CANNED FISH Pb Contamination of Pb in canned fish is attributed to:  the solder used in fabrication of can seams  Pb contained in the tin coating on tinplate. Cd  Cd is a common pollutant in harbours surrounded with industrial installations.  Cd is also widely used in metal plating.

SOURCES OF CONTAMINATION OF CANNED FISH Hg For Hg, once it is deposited into aquatic environment, micro-bacteria in water as well as sediments convert the inorganic Hg into the highly toxic methyl mercury. This form accumulates easily in aquatic organisms including fish. Limits on heavy metal intake levels in canned fish have been established in various countries in order to safeguard public health.

METHODOLOGY Sample Collection Total number of samples canned fish comprising  28 brands of Mackerel  25 brands of sardines  2 brands of pilchards  5 brands of tuna For each Canned fish sample, the fish sauce was carefully drained and a portion of the muscle homogenized and stored for analyses.

METHODOLOGY

RESULTS AND DISCUSSION

Range of values of metals in canned fishes from local markets in Ghana (µgg-1 wet weight) Metal MackerelSardinePilchardsTuna WHO/FAO Stds ( µ gg -1 ) (1996) Hg < (n = 85) (n = 74) (n = 6) (n = 15) 0.5 Cd < (n=68) <0.01 (n = 64) <0.01 (n = 6) < (n=13) 0.5 Pb < (n=71) < (n = 55) <0.01 (n = 3) < (n=10) 2.0 n: Number of samples analyzed,

The results of this study indicates that:  Canned fish from the Ghanaian market have concentrations well below the permissible FAO/WHO levels for these toxic metals (Hg: 0.5 µgg -1 ; Cd: 0.5 µgg -1 ; Pb: 2.0 µgg -1 ).  Their contribution to the body burden can therefore be considered negligible.

Provisional Tolerable Weekly Intakes (PTWIs) A Joint FAO/WHO expert committee on food additives has recommended a provisional permissible tolerable weekly intakes (PTWIs) of mercury, cadmium and lead at concentrations of 5, 7 and 25 µg/kg body weight respectively (FAO/WHO, 2004). For mercury the highest concentration was recorded in nampa tuna fish (0.2 µgg -1 wet weight).

An adult who weighs 60kg must consume about 1500g of the nampa tuna (150g /can) which is about 10 cans / week in order to accumulate 300µg of mercury in a week which is the limit set by FAO/WHO. This means that for the other species of fishes which have lower concentrations more than 10 cans / week will have to be consumed in order to accumulate that much of mercury in an adult which is highly unlikely for an individual.

For cadmium the highest concentration was recorded in Rising star tuna fish (0.45µgg -1 ). An adult who weighs 60kg must consume about 933g of the Rising star tuna fish (155g/can) which is about 6 cans / week in order to consume 420µg of cadmium the limit set by the FAO/WHO. Even though it is possible for one to consume 6 cans of the tuna each week, it is advisable not for one to consume a lot.

The highest lead concentration was recorded in B.B. sardine (1.44µgg -1 wet weight). A 60kg adult must consume about 1042g of the B.B. sardine (215g /can) which is about 5 cans / week in order to accumulate 1500µg of lead concentration which is the limit set by the FAO/WHO. Again, it is possible for one to consume that much of can fish per week, but it is advisable not to do so.

RECOMMENDATIONS Consumption of too much canned fish is not advisable. Taking uncanned fish should be encouraged More work should be carried out on other canned foods in Ghana. Crooked canned foods should not be purchased

CONCLUSION The results of this study shows that heavy metal concentrations in canned fish were below the permissible threshold levels of FAO/WHO. Their contribution to the body burdens can therefore be considered negligible.

WAY FORWARD Assessment of heavy metal levels in gari processing and their effects. Biochemical and mineral analyses of green leafy vegetables. Measures to mitigate iron toxicity incidence in rice fields

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