Researchers have warned that a common type of recycled plastic bottle introduces more potentially dangerous substances into its contents than newly manufactured bottles.

Brunel University London researchers discovered 150 compounds that leached into drinks from plastic bottles, with 18 of those chemicals found at levels exceeding safety standards.

They also discovered that drinks bottled with recycled Polyethylene Terephthalate (PET) can have higher quantities of pollutants than those bottled with new PET, implying that contamination may be caused by difficulties with the recycling process.

The researchers are advocating for more stringent recycling processes to remove potentially hazardous substances.

The thermoplastic PET is the third most often used form of plastic in food packaging, with single-use drink bottles being one of its most popular end uses. Such bottles are also one of the most common types of plastic litter, prompting a variety of campaigns to enhance PET recycling rates. A recent EU directive mandated that PET bottles have at least 30% recycled content by 2030.

Hazardous PET

However, PET is also known to be a source of several hazardous chemical pollutants, such as endocrine disruptors like Bisphenol A, which can cause reproductive issues, cardiovascular problems, and cancer, among other adverse effects.

The researchers examined 91 studies on chemical contamination from plastic bottles throughout the world. "We found these chemicals can come from various sources, such as the catalysts and additives used during production and degradation during PET production, and degradation that can happen across a bottle's lifecycle," said Dr. Eleni Iacovidou, a lecturer from Brunel's center for pollution research and policy, who led the study.

Contaminating the feedstock 

According to the article published in the Journal of Hazardous Materials, many of the pollutants detected in recycled PET bottles were caused by contamination of the feedstock, including labels. 

"This evidence suggests that highly recyclable products, such as PET drink bottles, can be inapt for closed-loop recycling when poorly designed, indicating the need for greater adoption of design-for-recycling principles and improvements at the waste-management infrastructure level," the researchers wrote.

The study argues that a technology known as the "super cleaning" process, which uses a three-stage process to clean old plastics before recycling – a high-temperature wash, a gas wash, and a chemical wash – could be used to minimize the number of chemicals detected in bottled drinks.

“Recycling processes already include the cleaning of the bottles before turning them into secondary raw material for use. By investing in new super-cleaning technologies, we can maximize the likelihood of decontaminating recycled PET to levels similar to virgin PET," a researcher said. 

The researcher added, however, that the ultimate solution to the problem is for society to begin an end to the use of PET altogether.

“We all have a responsibility to bear. We need to start thinking about how to prevent the use of PET bottles in our households by investing, for example, in water filters, or large water containers and learning how to dispose of our plastic waste properly,” she said.

“If we reduce our consumption of PET then we will drive change further up the system. Less demand equals less production in the first place.”

Read more: The ugly face of plastic production