Image copyright GETTY IMAGES Image caption The colour is pink and has a salmon-flavoured smell
Some hot food sold at McDonald’s, Burger King and KFC contains ingredients which are similar to those in illegal industrial chemicals.
Disposable coffee cups, cleaning products and laminated plastic packaging were also found to contain the colour pink industrial dye.
That pink colour and the smell are used to help fast food products stay bright but unhealthy.
The findings were published in the journal Plos One, an online medical journal.
Pink dyes are used in food colouring, which is intended to create the look of greenery.
But the colour is not allowed in the food industry, but the additive is used in non-food products including plastic packaging and marketing materials.
Pink dihydroxyphthalate, which the researches say is the pink pigments in pink food colouring, is suspected of being used illegally in fertilisers and pesticides.
Image copyright Getty Images Image caption Hot-food products which contain the chemical are sold by KFC, Burger King and McDonald’s
The researchers looked at food colourings made by three companies – 3M, Sigma-Aldrich and Solutia – and found that one of the chemicals had been a leading suspect in bans on pink dye in agriculture.
All three companies told the BBC they did not sell products in the UK made with pink dye.
But a 3M spokesman told BBC News: “3M is a highly regulated company that has a robust regulatory compliance process and procedures in place for all of our manufacturing, marketing and distribution operations.
“The safety of the food and beverage products in which our colours and proprietary ingredients are used cannot be guaranteed.”
Image copyright Getty Images Image caption The research authors have said they are worried the contaminants could be causing health problems
The researchers used tracking devices to trace the chemical formulas used at fast food restaurants in Manchester.
They then tested which products contained which ingredients using labelling software.
They detected a total of 14 references to the pink dye in products in fast food shops in the UK.
Other products which were also found to contain chemicals made with the same dye included certain disposable coffee cups sold by Starbucks and the additives in cleaning products sold by Prestige Clean.
Dr Hayley Maycock, the lead author of the study and a PhD student at King’s College London’s School of Public Health, said she was concerned about the impact of eating these fast food products on people’s health.
“One of the main reasons why these consumer goods are increasingly used is the lack of healthier alternatives,” she said.
“Industrial chemicals – like pinks – have no effect on the safety of food, but due to their high risk profile, their use in non-food products continues.”
She added: “Industrial chemicals are often still in the environment despite being banned in food. The risk posed to human health by some of these chemicals is therefore not fully understood.”
One of the scientists who performed the research has urged retailers to stop using the additives in products.
Marketing manager Anna Flint said the UK’s Food Standards Agency (FSA) was doing too little to safeguard people from industrial chemicals.
“These are the UK’s leading food dyes, but we know for a fact they are banned in farm-based use,” she said.
“What’s happening in the fast food industry should be policed.”