Tuna at a fish market
Credit: Wikimedia
PARIS: Tuna sushi bought at a range of U.S. restaurants and supermarkets had mercury that breached levels set by health watchdogs.
One hundred sushi samples were collected from 54 restaurants and 15 supermarkets in New York, New Jersey and Colorado, comprising 'akami' (lean red tuna) as well as 'toro' (fatty tuna) and reported in the British journal Biology Letters.
Mercury is a toxic chemical that is passed up the food chain, progressively accumulating in larger carnivores. Excessive mercury is linked especially to neurodevelopmental defects, including mental retardation, cerebral palsy, deafness and blindness.
Many countries have issued advisories notifying consumers about fish that are high in mercury, yet at the same time allow poor labelling of fish species, the paper says.
Safe: 0.1 mg per kg bodyweight per day
A leading benchmark for safety is a maximum daily consumption of 0.1 microgrammes of mercury per kilo of human bodyweight per day, set by the US Environmental Protection Agency (EPA).
Calculated on the basis of a 60 kg adult woman consuming a single order, samples of Bigeye tuna toro were found to have average mercury levels of 0.351 microgrammes per kilo, while Bigeye tuna akami had 0.344 microgrammes.
Bluefin toro samples had the equivalent of 0.123 microgrammes per kilo of bodyweight per day, and bluefin akami 0.180.
Exceed maximum daily consumption
Yellowfin tuna, found in the samples only as akami, had 0.164 microgrammes of mercury per kilo of bodyweight.
"The mean mercury concentrations of all samples exceed the concentration permitted by Japan and the maximum daily consumption considered safe by the U.S. Environmental Protection Agency," said the paper.
"Mean mercury levels for bluefin akami exceed those permitted by the U.S. Food and Drug Administration (FDA), Health Canada and the European Commission.
"On average, one order of Bigeye tuna sushi, the species used most often for sushi, exceeds the safe maximum daily dose recommended by Health Canada and the safe limit established by the World Health Organisation (WHO) and FAO [Food and Agricultural Organisation] for women of childbearing age."
Estimate your mercury exposure
An easy way to estimate your mercury exposure from eating fish is to check out the free online mercury calculator at www.gotmercury.org. Based on the current U.S. EPA and FDA guidelines, the mercury calculator is an excellent way to know your potential mercury exposure risk.