So many college staples turn out to be deadly. Leftover pasta, for instance, or pufferfish and cocaine. Well, we're afraid we have bad news for a surprising number of you; tuna contains the toxic heavy metal mercury and you may be eating it at levels deemed not safe.

In a study published in the journal Society of Environmental Toxicology and Chemistry, researchers at the University of California, Santa Cruz (UCSC) questioned students about their consumption of tuna and their knowledge of potential mercury poisoning resulting from eating too much of the fish. Samples of their hair to test for mercury levels were also taken.

They found that 54 percent of students reported eating three tuna meals per week, which potentially exceeds the maximum dose of methylmercury deemed safe by the Environmental Protection Agency (EPA). A shocking 7 percent of participants in the study reported eating more than 20 meals containing tuna a week. Tests on some of the students' hair revealed mercury levels in their bodies were above what is considered "a level of concern".

The lead researcher, Myra Finkelstein, says she was inspired to conduct the study after being shocked at hearing how much tuna some students ate.

"I've been dumbfounded when students have told me they eat tuna every day," Finkelstein said in a statement. "Their lack of knowledge about the risk of exposure to mercury is surprising."

This was reinforced by the study, which found that students lacked knowledge of mercury in tuna, as well as confidence in their knowledge, with over 99 percent of participants reporting low knowledge and low confidence in their survey answers.

"It was not a large sample size, but only one out of 107 students surveyed had a high level of knowledge as well as confidence in that knowledge," Finkelstein said. The majority of students surveyed thought that it was safe to eat two to three times as much tuna as is recommended by the EPA, which is two to three servings per week.

Tuna contains methylmercury, a substance more toxic than inorganic mercury, which can accumulate in the body. Too much of it can result in methylmercury poisoning, which can cause poor cognitive function, blindness, and impaired lung function.

The doses seen in samples collected from students were concerning, but not alarming.

"It doesn't necessarily mean that they would be experiencing toxic effects, but it's a level at which it's recommended to try to lower your mercury exposure," Finkelstein said.

Her team discussed the study with the UCSC administrators who oversee the dining halls, who have now put up signs and will give students information about mercury in tuna and safe levels of consumption.