WeWork, the co-working empire once valued at $47 billion before reality struck, plunging the business and its investors into crisis, has another problem to add to its growing pile — one which doesn’t exactly reflect well on its core business of kitting out and maintaining modern working environments.

The problem is a safety concern affecting users of WeWork co-working spaces in the U.S. and Canada. Today the company emailed members in the regions to warn that around 1,600 phone booths installed at WeWork locations have been found to have elevated levels of formaldehyde — which it warns could cause health issues for people exposed to the gas.

WeWork blames the issue on a manufacturer of the booths.

The booths are provided in its co-working spaces for WeWork members to be able to take calls in private — given other common areas are shared by all users.

“After a member informed us of odor and eye irritation, WeWork performed an analysis, including having an outside consultant conduct a series of tests on a sampling of phone booths. Upon receiving results late last week, we began to take all potentially impacted phone booths out of service,” it writes in an email to members.

Affected phone booths “are being taken out of service immediately, and will be removed from your location as soon as possible,” it adds.

In addition to ~1,600 booths it has confirmed are affected, a further 700 booths are being taken out of service in what WeWork describes as “an abundance of caution” — i.e. while it carries out more checks — with the promise of a further update once it has concluded its tests.

Members wanting to know which booths are safe to use in the meanwhile are told to contact the community team at their WeWork location.

WeWork also says alternative quiet spaces will be provided, such as in conference rooms and unused offices.

Discussing the health risks of formaldehyde gas — a chemical which is used in various building materials –WeWork’s email warns: “Short-term exposure to formaldehyde at elevated levels may cause acute temporary irritation of the nose, throat, and respiratory system, including coughing or wheezing. These effects are typically transient and usually subside after removal of the formaldehyde source.

“Long-term exposure to formaldehyde, such as that experienced by workers in jobs who experience high concentrations over many years, has been associated with certain types of cancers. You can find additional information in this FAQ from the Occupational Safety and Health Administration.”

The email encourages any WeWork members with health concerns to contact a doctor.

A tipster who sent us the email reported experiencing a sensation of “burning eyes” after using the booths.

They also said several people in their team had experienced the same issue.

“Some complained that they felt nauseous after spending time inside the booths,” the tipster wrote. “I never felt that, but the burning eyes was 100% there for me several times. Scary stuff.”

Reached for comment, a WeWork spokesperson confirmed the formaldehyde issue, saying it’s taking “a number” of booths out of service at “some” locations in the U.S. and Canada — due to “potentially elevated levels of formaldehyde caused by the manufacturer.”

“The safety and well-being of our members is our top priority, and we are working to remedy this situation as quickly as possible,” it adds in a statement.

It is not clear exactly how many WeWork locations contain affected booths at this point.

Nor has WeWork provided more detailed information about how long members might have been exposed to elevated levels of formaldehyde — with its email merely suggesting some of the booths have been in place for “months.”

“The potentially impacted phone booths have been installed over the past few months, exact timing varies based on location,” it writes.

Although clearly the level of exposure will vary from person to person depending on their use of the booths.

The company did not respond to a question asking whether any of its international WeWork locations are affected by the issue.