Besides 550 calories and a yummy special sauce, the ever-popular Big Mac contains in its buns azodicarbonamide, a chemical found in yoga mats and shoe soles that Subway just dropped from its sandwich bread.
That food fact was revealed Sunday by N.Y. Sen. Chuck Schumer as he called on the Food and Drug Administration to ban the chemical altogether.
Schumer said the chemical is banned "in most of the developed world."
Last week, Subway said it would voluntarily remove azodicarbonamide, a chemical that makes texture more consistent, as part of its "bread improvement efforts."
Vani Hari, an activist blogger known as the Food Babe, was declaring victory for the announcement, after she had garnered more than 57,000 signatures on a petition to ask Subway to reformulate its bread recipe. Subway already sells azodicarbonamide-free bread in its overseas markets.
"When you look at the ingredients, if you can't spell it or pronounce it, you probably shouldn't eat it," said Hari, who was also behind a campaign to get Kraft to remove yellow dyes from three of its child-friendly Mac & Cheese products.
The World Health Organization has linked this chemical additive to respiratory issues, allergies and asthma, and it is banned in Europe and Australia. Azodiacarbonamide is legal in the United States and Canada.
But Jeff Stier, director of the risk analysis division of the National Center for Public Policy Research, a conservative Washington-based think tank, was critical of Schumer's call to ban azodicarbonamide, saying it sets a "dangerous policy precedent."
"If this is the new standard, obesity isn't going to be a problem anymore -- starvation is," he said.
"[Schumer] is allowing the Food Babe to dictate policy based on the notion that the chemical also appears in yoga mats, therefore it is harmful," Stier told ABCNews.com. "Is he saying we shouldn't trust the FDA's food scientists?"
The FDA considers the chemical safe and so does McDonald's.
In a prepared statement, McDonald's said that azodicarbonamide is a "common food additive and is used in many items on your grocer's shelves, including many hot dog buns and other bread products that you probably already purchase."
"I think there is a bit of confusion because there is an industrial strength grade variation of the ingredient, and that version is used in yoga mats," McDonald's spokeswoman Lisa McComb told ABCNews.com. "There's another version that's approved by the FDA and safe for bakers.
"Just to give an analogy that might make sense, there is salt to de-ice your driveway and salt you use in the kitchen. They are both sodium chloride," she said. "These long, scientific names do sound a little scary, but it's a good thing that people are looking more into what they really eat. ... We do look at the science absolutely. And we do listen to consumers."
When asked, she did not say whether McDonald's would follow Subway's example.
"We are focused on our menu and are looking at our ingredients on an ongoing basis," McComb said. "We are always doing that."
The FDA allows azodiacarbonamide to be used as an "aging or bleaching" ingredient in cereal flour if it does not exceed 45 parts per million. It is also approved for use as a "dough conditioner" in the same proportions.