The Food Safety Authority has issued a warning over the consumption of shark, swordfish, marlin and tuna by pregnant women and young children.
Studies have found high mercury levels in these species, which could affect the human nervous system and the developing brain.
The authority has advised pregnant and breastfeeding women, women of childbearing age, and young children to avoid swordfish, marlin and shark and to limit their consumption of tuna to one fresh tuna steak per week, or two 8 oz cans of tuna.
All other consumers have been advised to restrict their consumption of shark, swordfish and marlin to not more than one portion per week. However, they have not been advised to limit their consumption of tuna as it does not pose as high a risk.
Mercury is found naturally in the environment but also as a result of the disposal of waste or releases from industrial activities.
A recent European Food Safety Authority study found that its chemical form - methylmercury - is prevalent in all fish. It can build up to significant levels in large predatory fish as they consume smaller species that have also taken up mercury.
Tinned tuna poses a lower risk because smaller fish are used in this product. Exposure during pregnancy is considered the most critical period for methylmercury toxicity because unborn babies and young children are the most vulnerable to its effects. The consumption of shark, swordfish, marlin and fresh tuna is relatively low in this State, according to Mr Alan Reilly, acting chief executive of the Food Safety Authority.
"Consumption, however, in relation to tuna is increasing, especially in relation to canned tuna, so we would caution pregnant and breastfeeding women as well as young children to not exceed the consumption of two 8 oz cans of tuna per week," he said. The Food Safety Authority has encouraged people to continue eating other fish as part of a balanced diet.
"The proven association between omega-3 fatty acids found in oily fish and reduced heart disease is a strong motivator for people to consume fish and we would hope that people continue to consume fish," Mr Reilly said.
"There is a wide range of fish available offering everyone a range of healthy options."
