So-called “eco-friendly” paper drinking straws contain long-lasting and potentially toxic chemicals and may not be better for the environment than plastic versions, researchers have warned.

Long-lasting “forever chemicals”, which are potentially harmful to people, wildlife and the environment, were found in 18 out of 20 brands of paper straws, Belgian researchers found.

A growing number of countries, including the UK and Belgium, have banned the sale of single-use plastic products, including drinking straws, and plant-based versions have become popular alternatives.

In the first analysis of its kind in Europe, and only the second in the world, the researchers tested 39 brands of straws for the group of synthetic chemicals known as poly- and perfluoroalkyl substances (PFAS).

PFAS were found in the majority of the straws tested and were most common in those made from paper and bamboo, the study, published in the peer-reviewed journal Food Additives and Contaminants, found.

Thimo Groffen, an environmental scientist at the University of Antwerp, said the team of researchers wanted to find out if PFAS were in plant-based drinking straws sold in Belgium, after they were discovered in straws sold in the US.

Straws made from plant-based materials... are often advertised as being more sustainable and eco-friendly than those made from plastic. The presence of PFAS in these straws means that's not necessarily true

The team bought 39 brands of drinking straw made from five materials – paper, bamboo, glass, stainless steel and plastic – mainly from shops, supermarkets and fast-food restaurants, before putting them through two rounds of testing for PFAS.

The majority of the brands – 27 out of 39, or 69% – contained PFAS, with 18 different PFAS detected in total.

The paper straws were most likely to contain PFAS, with the chemicals detected in 90% of the brands tested.

PFAS were also detected in four out of five brands of bamboo straw, three out of four of the plastic straw brands, and two out of five of the glass straws.

They were not detected in any of the five types of steel straw.

The presence of the chemicals in almost every brand of paper straw means it is likely it is, in some cases, being used as a water-repellent coating, the researchers said.

The study did not look at whether the PFAS would leach out of the straws into liquids.

The most commonly found PFAS, perfluorooctanoic acid (PFOA), has been banned globally since 2020.

Also detected were trifluoroacetic acid (TFA) and trifluoromethanesulfonic acid (TFMS), “ultra-short chain” PFAS which are highly water soluble and so might leach out of straws into drinks, according to the report.

The researchers said the PFAS concentrations were low and, bearing in mind that most people tend to only use straws occasionally, posed a limited risk to human health.

However, PFAS could remain in the body for many years and concentrations could build up over time, the team warned.

PFAS are used to make everyday products, from outdoor clothing to non-stick pans, resistant to water, heat and stains.

They break down very slowly over time and can persist over thousands of years in the environment, a property that has led to them being known as “forever chemicals”.

They have been associated with a number of health problems, including lower response to vaccines, lower birth weight, thyroid disease, increased cholesterol levels, liver damage, kidney cancer and testicular cancer.

Dr Groffen said: “Small amounts of PFAS, while not harmful in themselves, can add to the chemical load already present in the body.

“We did not detect any PFAS in stainless steel straws, so I would advise consumers to use this type of straw – or just avoid using straws at all.

“Straws made from plant-based materials, such as paper and bamboo, are often advertised as being more sustainable and eco-friendly than those made from plastic.

“However, the presence of PFAS in these straws means that’s not necessarily true.”