A new study suggests Americans may be consuming dangerous amounts of trans fats and not even know it.

Despite a push from the U.S. Food and Drug Administration (FDA) to phase out artery-clogging trans fat, a study released by the Centers for Disease Control and Prevention (CDC) says it can still be found in nearly 1 in 10 processed food products in the United States.

The FDA has declared that trans fat, which is the product of partially hydrogenated oils (PHOs), is not “generally recognized as safe” for consumption and is a risk factor for cardiovascular disease.

“The sense is that trans fat is mostly gone from foods, and what we see is there’s still a lot being used in packaged foods,” said Christine Curtis, assistant commissioner in the New York City Health Department and an author of the study.

The study found that due to a federal loophole, consumers may be unaware that the foods they are eating contain trans fat. Of the 4,340 products analyzed, 391 listed partially hydrogenated oils in their ingredient information, but 330 of those products claimed to have zero grams of trans fat per serving on the nutritional label, the San Francisco Chronicle reports.

The loophole allows for products with less than 0.6 of a gram per serving to claim zero trans fat on the nutritional label. However, eating three servings of a product that contains 0.5 of a gram of trans fat per serving may lead an unaware consumer to eat 1.5 grams of trans fat, according to the Chronicle.

“We think consumers are unknowingly consuming artificial trans fat and the recommendation is to consume as little as possible,” she told the San Francisco Chronicle.

The study also suggests an FDA ruling to ensure that restaurant customers are protected from industrial trans fat.