The Environmental Protection Agency’s own staffers objected to a controversial new US rule governing the use of cancer-causing asbestos, according to internal emails.

The rule, issued in June, would require manufacturers to receive EPA approval before importing or manufacturing asbestos for certain purposes. The highly technical regulation has prompted controversy, with the agency saying it more tightly regulates asbestos, but critics saying it could allow the substance to be more widely used in America.

Many developed nations ban asbestos altogether, but the United States has restrictions that fall short of an outright ban.

Internal emails obtained by the New York Times show that staffers at the EPA objected to the provisions.

“The new approach raises significant concerns about the potential health impacts,” policy analyst Sharon Cooperstein wrote in one of the e-mails.

The new rule identifies 15 uses of asbestos that require approval, instead of requiring a review for all new uses.

The staffers worried that could allow companies to get away with using asbestos in ways the agency did not list.

“This new approach allows asbestos-containing products that are not currently used to be used in the future. There are many uses of asbestos beyond the 15 identified,” wrote Mark Seltzer, an EPA attorney, in another email published by the Times, adding the approach “hampers enforcement, compliance, and information gathering”.

Robert Courtnage, an associate chief in the agency’s Office of Pollution Prevention and Toxics, wrote that it was “upper management” that ordered the new approach, against the recommendations of staff.

An EPA spokesman told the Times that the staffers, like outside critics, did not fully understand the proposal.

Friday is the last day for the public to submit comments on the plan, before it is finalized later this year.