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 lg kg1 body weight respectively (FAO/WHO, 2004).
For mercury the highest concentration obtained for this study
was recorded in Nampa tuna fish (0.2 lg g1 wet weight). An adult
who weighs 60 kg must consume about 1500 g of the Nampa tuna
(150 g per can) which is about ten (10) cans per week in order to
accumulate 300 lg of mercury in a week which is the limit set
by FAO/WHO Expert Committee on food additives. This means that
for the other species of fishes which have lower concentrations
more than 10 cans per week will have to be consumed in order
to accumulate that much of mercury in an adult which is highly
unlikely for an individual. Moreover the eating habits of Ghanaians
are such that the consumption rate of canned fish is quite low even
though data on the rate of consumption of canned fish in Ghana is
unavailable. For cadmium the highest concentration obtained for
this study was recorded in Rising star tuna fish (0.45 lg g1). An
adult who weighs 60 kg must consume about 933 g of the Rising
star tuna fish (155 g per can) which is about six (6) cans per week
in order to consume 420 lg of cadmium the limit set by the joint
FAO/WHO Committee (2004). Even though it is possible for one
to consume six (6) cans of the tuna each week, most Ghanaians
prefer taking their fish in other forms such as fried, salted etc. So
the rate of consumption of canned fish is low even though data
on the rate of consumption of canned fish in Ghana is unavailable.
The highest lead concentration was recorded in B.B. sardine
(1.44 lg g1 wet weight). A 60 kg adult must consume about
1042 g of the B.B. sardine (215 g per can) which is about five (5)
cans per week in order to accumulate 1500 lg of lead concentration
which is the limit set by the joint FAO/WHO Committee
(2004) for 60 kg weight of an adult. Again, it is possible for one
to consume that much of can fish per week but the eating habits
of Ghanaians as discussed before is such that the consumption rate of canned fish is quite low even though data on the rate of consumption
of canned fish in Ghana is unavailable.