CHICAGO (CBS) — “Mystery meat” has been a staple in school lunchrooms for decades, but now the federal government is reportedly buying millions of pounds of ground “pink slime” that has raised serious concerns from scientists.

The ground-up meat is treated with ammonia to kill salmonella and E. coli. The bright pink slimy substance is a combination of beef leftovers and connective tissue. It is then blended into ground beef.

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And the U.S. Department Of Agriculture is buying seven million pounds of it as part of the national school lunch program, The Daily reports.

According to the USDA, The National School Lunch Program provides nutritionally balanced, low-cost or free lunches to eligible children each school day.

Carl Custer, a retired scientist who worked for the Food Safety Inspection service, told the Daily that buying the “pink slime” is a bad idea and hardly “nutritionally balanced.”

“My main objection was that is was not meat,” he said.

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Custer said it is simply not nutritionally equivalent to ground beef and considers it a “high risk” product.

To make matters worse, the ammonia used to treat this stuff can be harmful to eat and even has potential to turn into ammonium nitrate — a common component in homemade bombs, according to MSNBC.

The concerns over the product led fast food giants, including McDonald’s and Burger King, to reject it.

Custer said inspectors were pressured to approve the use of the meat for the school lunch programs across the country.

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The USDA asserts that its ground beef purchases “meet the highest standard for food safety,” the Daily reported.