Cecilia Williams has studied three chemicals on behalf of the WHO agency IARC. Photo: Jon Lindhe, KTH

Published Sep 29, 2026

Three common additives used in the plastics industry may cause cancer. A World Health Organization working group’s review of research highlights the danger posed by three common "plasticisers" – or softening agents – used plastic production.
“These plasticisers have been in use for over 50 years and are found, for example, in plastic flooring, cables and paints, and were previously used in cosmetics,” says Professor Cecilia Williams, who participated in the review project with the WHO International Agency for Research on Cancer (IARC).

IARC coordinates international research into the causes of cancer and develops strategies for cancer prevention. Every year, it sets up working groups to review all research on selected suspected carcinogens. These groups are responsible for producing scientific evidence (published in monographs) that governments and the WHO use for legislation and preventive health policies. 

In the latest review, 21 researchers took a closer look at three phthalates (BBP, DBP, DINP), chemical compounds derived from phthalic acid that are used to soften hard plastics and are commonly found in everyday items. 

“They are absorbed and accumulate in food, particularly fatty products such as oil and dairy products, but we are also exposed to them via the air and through our skin,” Williams says. “Phthalates are very common; their metabolites can be detected in virtually everyone. They are therefore also known as everywhere chemicals.” 

A challenging task 

The researchers – who come from the U.S., Canada, Australia, Japan, Mexico, France, Germany, Algeria, Switzerland, Italy, Norway and Sweden – have reviewed several hundred scientific articles. In June, they met at the IARC headquarters in Lyon, France to debate and try to reach a consensus. Representatives from the companies that produce and use these phthalates attended as observers. 

“In Lyon we worked for eight days straight, from morning until evening. We then rewrote our chapters to reflect the consensus, often late into the night,” Williamson says.  

“It was hard work. This work has such a significant impact, so we really wanted to be sure of what we were writing and putting our names to.”  

The researchers agreed that it is possible that the three phthalates cause cancer in humans. The IARC classifies substances into three categories: 1 – carcinogenic to humans; 2A – probably carcinogenic; 2B – possibly carcinogenic; 3 – cannot be classified as carcinogenic. All three phthalates were classified as Group 2B. 

“This will most likely influence future legislation and lead to the industry phasing out these chemicals,” she says. Neverthless, they will probably be replaced by other variants, she says.  

“Plasticisers are needed in plastics manufacturing.”  

Jon Lindhe

Contact Cecilia Williams