When you’re out running around on a crazy busy day and you find yourself suddenly famished and needing to eat right now, there just aren’t many good options, especially if you’re trying to avoid meat and processed foods.

Like many people, Subway has turned into my go-to in such situations, and I’m exactly the kind of customer they’re trying to attract by marketing themselves as a fresh and healthy fast-food alternative. (I usually get a foot-long Veggie Delight with everything but jalapenos — extra black olives, please!)

But the largest restaurant chain in the world and America’s top fast food chain eight years running has a dirty little secret – actually several of them, it turns out.

I ran across an article last week announcing that Subway is responding to public pressure and removing a chemical called azodicarbonamide from all of its breads because of a customer-driven protest.

According to the Center for Science in the Public Interest, commercial bakers add azodicarbonamide to bread as a dough conditioner to make it have a nice, chewy texture. The plastic-based industrial chemical is also widely used in things like yoga mats and shoe soles to give them more elasticity. Seriously.

That sounds wrong just on general principle, but it is actually much worse than that: when ingested, azodicarbonamide breaks down into other substances, such as urethane, a known carcinogen, and semicarbazide, which causes lung and blood vessel cancers in mice.

Besides widespread use in bread and buns in fast-food chains, grocery store breads and restaurant breads also contain this nasty stuff, which aside from being carcinogenic has been linked to respiratory issues, allergies and asthma by the World Health Organization.

How does that nice, soft bread taste now, huh?

One of the biggest clues that this chemical should not be in the American food supply is that azodicarbonamide is banned as a food additive in the U.K, European Union, Australia, and Singapore, where you can get 15 years in prison and a $450,000 fine for using it in food.

Subway doesn’t put azodicarbonamide in its bread sold in those countries, so why should it do so here? Indeed, why should anybody? And why does the FDA even allow it?

This issue all came to a head for Subway earlier this month when food blogger Vani Hari, over at FoodBabe.com, launched a petition urging Subway to stop using azodicarbonamide. Nearly 90,000 people have now signed it, and Subway immediately sat up and took notice.

As well it should: Hari was the driving force behind the recent removal of artificial yellow dyes in at least three Kraft Mac and Cheese products and for Chick-fil-A removing controversial chemical ingredients from its menu, so she is a well-watched touchstone of consumer food activism with a formidable following.

Hari’s petition pressured Subway to make the change on azodicarbonamide, and I really hope she targets the FDA next on this issue. But the bad bread is only part of what she learned about Subway’s ingredients after researching the chain’s food supply since 2012.

She also found chemical additives, nitrates, GMOs, and refined sugars and flours in Subway’s products. And not only are all the veggies commercially grown and non-organic, she discovered that preservatives and artificial colors are added to some of them, such as banana peppers and pickles. Some of the salad dressings contain artificial colors, preservatives, and chemical additives as well.

Not even my extra black olives are safe.

“The ingredients for the black olives unveiled a new additive I learned about,” she wrote on her blog. “Ferrous gluconate, which is an iron-based preservative that helps keep olives black.”

And this, we are all assured, is how to Eat Fresh.

“What really upset me was it was something I always ate while on the road that I thought was healthy — their nine-grain bread and veggie sub and all the marketing about low calories and weight loss,” Hari told ABC News in early February.

“And they have an American Heart Association logo and stamp on their sandwiches,” she said. “I really had the illusion of healthy eating. When I saw what was actually in the bread, I was horrified.”

As we all should be, for oh so many reasons. But even with all of this news, Subway is still by far the healthiest choice of all the fast-food pressed on the American public. Now that, is truly horrifying.