As part of the Catalyst program in 2015, we analysed mercury concentrations in Australian fish including three tins of canned tuna purchased from the supermarket. Our laboratory is well equipped to measure mercury concentrations in fish. Whether mercury is harmful or not also depends on the amount of fish you eat and how often. Pregnant women are advised to limit their fish intake because of placental transfer of mercury to the unborn foetus and the effect of mercury on neural development. The dose for pregnant women is approximately half this value – 1.6 micrograms per kilogram of body weight per week). 1,000 micrograms (µg) is 1 milligram (mg).(The guidelines assume all mercury in fish is present as the more harmful methylmercury as a worst case scenario). The maximum dose of mercury set for the general population is 3.3 micrograms per kilogram of body weight per week. This limit is known as the “provisional tolerable weekly intake” or PTWI. In other words, how much mercury you can safely have from all food sources (not just fish). After all, it is the dose that makes the poison.īased on international guidelines, Food Standards Australia New Zealand also provides recommended safe limits for dietary intake. However, whether mercury is harmful or not also depends on the amount of fish you eat and how often. Two separate maximum levels are imposed for fish ― a level of 1.0 mg mercury/kg for the fish that are known to contain high levels of mercury (such as swordfish, southern bluefin tuna, barramundi, ling, orange roughy, rays and shark) and a level of 0.5 mg/kg for all other species of fish. So, the fact the canned tuna in Australian cupboards is likely to contain smaller species is already a bonus when it comes to reducing mercury risk.īut let’s drill down to the details. Skipjack are the smallest of the major tuna species, while yellowfin are larger. Skipjack and yellowfin are the main tuna species listed as ingredients in canned tuna in brands sold at Australian supermarkets. So this concern has largely been associated with the use of tuna species such as albacore and larger tuna specimens. Mercury concentrations are higher in predatory fish such as tuna and generally increase with age and size. Over the years, some scientists have raised concerns about high concentrations of mercury in canned tuna. Shutterstock Tuna in Australian cupboards is likely smaller species Tinned tuna is cheap, tasty and nutritious. But to make matters worse, a substantial proportion of mercury in fish is present as methylmercury – a potent neurotoxin formed by bacteria in waters and sediments.Īlthough mercury pollution has increased since industrialisation, accumulation of methylmercury in animals is a completely natural phenomenon.Įven fish caught from the middle of the ocean, far from any polluting sources, will contain methylmercury. Most forms of mercury are potentially very toxic to humans. So the bigger the fish, the higher the likely mercury content. In other words, it builds up as smaller fish get eaten by middle-sized fish, which get eaten by large fish, which get eaten by us. Mercury is naturally present in our environment but can biomagnify to relatively high concentrations in fish – particularly predatory fish. That’s a level even the most keen tuna-lover would be hard pressed to consume.Īustralia’s gold industry stamped out mercury pollution - now it's coal's turn Lab tests we did for the ABC TV science program Catalyst in 2015 suggest – depending on your body weight and the exact brand of tuna you buy – you could eat anywhere between 25 and 35 small tins (95g each) of tuna a week before you hit maximum mercury limits. It is safe for everyone (including pregnant women) to consume canned tuna as part of their fish intake.Ĭanned tuna generally has lower levels of mercury than tuna fillets because smaller tuna species are used and the tuna are generally younger when caught. Sounds good, but how much can you eat before you need to worry about mercury?Īccording to Food Standards Australia New Zealand: A tin of tuna is significantly cheaper than many types of fresh meat or fish. For as little as A$1 a tin, canned tuna is an excellent, affordable source of protein, polyunsaturated fats and other nutrients.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |