A potentially hazardous chemically used to make rubber and yoga mats is being used in nearly 500 food products sold in US stores, according to a report.
Azodicarbonamide, known as ADA, is a chemical used as an oxidising agent in dough and to give bread a longer its shelf-life.
The chemical, which is banned in the UK, Europe and Australia, is also used to give plastics more elasticity and make yoga mats, shoe rubber and other rubber items.
Sandwich chain Subway recently announced it has begun to remove all ADA from its bread following a campaign from blog FoodBabe.com.
It later emerged that ADA is also being used by other fast food giants such as McDonald's, Burger King and Dunkin' Donuts in the US.
A second healthy food advocate group has now revealed that the chemical is used as an ingredient in hundreds of food items in stores across the US.
The Environmental Working Group (EGW), based in Washington, has published a list of 500 foods which use azodicarbonamide as an ingredient, inclduding those advertised as healthy.
Among the items include English muffins sold by Weight Watchers, as well as products produced by well-known brands including Pillsbury, Sara Lee, and Shoprite.
Vani Hari, creator of FoodBabe.com, said: "It's unacceptable that major food companies are using an unnecessary and potentially harmful chemical in their products, when it's clear they can make food without it.
"These questionable additives are not supposed to be food or even eaten for that matter, but they do end up in the US food supply and are consumed by millions of people, including children, every day."
The World Health Organisation has linked the chemical to respiratory issues, allergies and asthma. The UK Health And Safety Executive has recognised azodicarbonamide as a potential cause of asthma.
Howver, the chemical is fully approved for use in food by the United States Food and Drug Administration (FDA) and the Canadian Food Inspection Agency. The FDA states that azodicarbonamide is safe for consumption if the amount in flour does not exceed 2.05 grams per 100 pounds of flour or 45 parts per million.
Despite this, Hari and EGW have said they will continue their efforts to get food companies to stop using the chemical in their food.
"As my campaign has shown, social media and grassroots advocacy can shake up the food industry and produce real change on behalf of consumers," Hari said. "I will continue to work with EWG and others to keep the pressure on to get these industrial chemicals out of our food."
Click here to see the full list of foods that contain ADA.