Eight styles of women’s shoes are being recalled globally by Clarks after tests found toxins in the products, the British retailer announced Thursday.

“Some samples of these shoes identified excessive levels of the chemicals benzidine or dimethoxybenzidine that are found in azo dyes and are restricted in some jurisdictions,” Clarks said in a news release. “Prolonged and direct contact with the shoes’ upper material can expose the wearer to these chemicals, which are toxic and can cause adverse health effects.” 

A potentially cancer-causing substance, benzidine is a synthetic chemical that has not been sold in the U.S. since the mid-1970s, according to the National Cancer Institute. The U.S. used large amounts of the chemical in the past for uses such as making dyes for cloth, paper and leather. 

The recalled shoes include the Breeze style in the Americas and the Brinkley style elsewhere, in all navy or dark navy-blue colored and introduced for the spring/summer 2022 season, Clarks stated. 

The following styles are affected: Brinkley Step in navy; Breeze Step in navy; Breeze Step in navy/white; Breeze Step in dark navy; Breeze Ave in dark navy; Brinkley Ave in dark navy; Brinkley Shore in navy; and Breeze Shore in navy.

People can determine if their shoes need to be returned by checking the product’s article number, the first eight digits of the 12-digit number under the size and fit information on a label inside the footwear. 

People who purchased a pair of the recalled shoes can visit here for a step-by-step guide to getting a refund. Those with questions are encouraged to consult the company’s recall website or by emailing productrecall@customerreply.clarks.com. U.S. customers can call the company toll-free at (800) 480-5992 from 6 a.m. to 6 p.m. Eastern.

Based in Somerset, England, Clarks was founded in 1825 and operates in more than 100 markets around the world.