Hazardous chemicals used in manufacturing clothes remain in garments even after they have been washed, according to new research.

Researchers at Stockholm University found that out of 60 garments from international brands, thousands of chemicals were present in the clothes and around 100 substances were preliminary identified. Some of them are suspected or proved carcinogens, while others have aquatic toxicity. 

Several of the substances were not on the producers’ lists and are suspected to be by-products, residues or chemicals added during transport. 

Exposure to these chemicals increases the risk of allergic dermatitis, and could be related to more severe health problems, the research claims.

High concentrations of quinolines and aromatic amines, were found in polyester, while cotton contained high concentrations of benzothiazoles – even clothes made from organic cotton.

After washing the clothes, some of the substances had disappeared, with a risk of ending up in aquatic environments. Others remained to a high degree in the clothes, becoming a potential source of long-term dermal exposure. 

However, the researchers said it is difficult to know if the levels of these harmful substances are hazardous, and what effects chemicals in our clothes can have in the long run.

“We have only scratched the surface, this is something that has to be dealt with,” says Conny Östman, professor in analytical chemistry. “We must find out if textile chemicals go into our skin and what it means to our health. It is very difficult to assess and requires considerably more research.”