The Centers for Disease Control and Prevention oversees a backlog of 142 applications from manufacturers of air-filtering masks such as N95s, which the agency was criticized as being slow to recommend over cloth masks before updating its guidance Friday.

The National Institute for Occupational Safety and Health, a part of CDC, has yet to review dozens of applications from manufacturers seeking regulatory approval to sell N95s, according to its website. Some of these applications have sat at CDC for months. One application submitted to the center in April was not completed until late December.

“NIOSH should make their way through the backlog and approve (or disapprove) more masks! More choice is good for consumers,” Megan Ranney, academic dean of the Brown University School of Public Health and co-founder of the Get Us PPE organization that delivers protective equipment, said in an email.

The backlog contributed to masks stacking up in their warehouses even as COVID-19 cases skyrocketed, according to American-based N95 manufacturers, many of whom began making protective equipment like masks for the first time during the pandemic.

Without NIOSH approval, makers of N95s cannot advertise on the same social media sites like Amazon and Facebook where ads for counterfeit KN95s and cloth masks are ubiquitous. Amazon, Facebook and Google can be slow to recognize certification, say manufacturers, with even some NIOSH-approved N95s still being blocked from the sites. Facebook did not respond to requests for a comment.

“For face masks marketed as N95 and KN95, we have implemented a rigorous seller vetting and product review process to ensure compliance with applicable laws, regulations, and Amazon policies,” said an Amazon spokesman, including inspecting supplier invoices, reviewing packaging and comparing against the CDC’s counterfeit mask list. Google responded with similar comments.

“NIOSH has really been inundated with applications and I know they’re doing the best they can given their relatively small size and being understaffed,” said Dan Glucksman, public affairs director for the International Safety Equipment Association, a lobby for protective equipment makers.

The laboratory within NIOSH that approves respirators has 88 employees, with 35 working full-time on respirator approvals, according to the agency.

Before the pandemic, NIOSH received six to eight requests per year from companies seeking to become new approval holders, said spokeswoman Stephanie Stevens. In 2021, there were 139 requests from new entities pursuing NIOSH approval.

CDC’s guidance

Meanwhile, President Joe Biden is announcing on Wednesday that he plans to make 400 million high-filtrating masks available to the public for free through drugstores, community centers and other locations.

Under pressure from public health experts, CDC updated its guidance on Friday to reflect the superior protection from N95s over other types of masks and removed language suggesting a shortage of N95s.

“Masks and respirators can provide varying degrees of protection, with well-fitting National Institute for Occupational Safety and Health (NIOSH)-approved respirators offering the most protection,” the website reads.

By definition, a N95 must filter at least 95 percent of airborne particles. Cloth masks filter at least 20 percent of particles, while medical masks do not reliably filter out smaller airborne particles, according to the Johns Hopkins Center for Health Security.

Even as COVID-19 caseloads shatter records, CDC Director Rochelle Walensky has added caveats when suggesting the use of highly protective N95 masks, saying they may be uncomfortable for some to wear.

And the CDC website reflects that message.

“Some masks and respirators offer higher levels of protection than others, and some may be harder to tolerate or wear consistently than others,” the site reads. “It is most important to wear a well-fitted mask or respirator correctly that is comfortable for you.”

NIOSH said in a statement that it issued 750 “approval decisions” last year. CDC confirmed it uses the term “approval action” to refer to decisions such as denials, too.

Some mask makers say that CDC’s urgency around N95s changed after the pandemic’s first winter wave in 2020.

Gary Warren, CEO of medical manufacturing company ivWatch LLC, said federal officials encouraged investment in medical grade N95s in August 2020. But by February 2021, he said CDC’s attitude had flipped.

“It wasn’t like, ‘We’ll help you get through’ anymore. It was like, ‘Are you sure you want to be in this market?’” Warren said.

His company only received approval to market his masks as N95s in November 2021 after applying in April.

Warren is among those who say online retailers are not always quick to recognize NIOSH approval.

Warren’s N95 operation, which falls under a subsidiary called blox, received 42 rejection letters from Amazon. The last rejection warned that more attempts to advertise on the site would lead to his account being suspended.

“I feel like I’m living in Alice in Wonderland,” said Warren, who said he invested $3 million into changing his supply lines to make N95s.

“We have been trying to deal with Google and Facebook to allow us to advertise and they will not,” said Claudio Dente, president of another manufacturer, Dentec Safety Specialists. “CDC/NIOSH lists every manufacturer and product that is certified on their website. We have told Google this and it does not matter to them.”

The American Mask Manufacturer’s Association estimated in a letter to the Biden administration last winter that it could produce 298 million U.S.-made N95 respirators and 671,000 reusable respirators each month.

The group began redoubling its efforts to get the administration’s attention recently as the omicron variant spread, using Twitter and voicemails to White House COVID-19 operations director Jeffry Wexler on Dec. 22 and Dec. 29.

“I said there’s over two dozen U.S. domestic manufacturers in AMMA and that we’re looking to help. We have hundreds of millions of N95s and surgical masks ready to go instantly,” said AMMA President Nicolas Smit. “Then we also have the capacity to make hundreds of millions of N95s as well, so we can help protect the American public right now and keep sending PPE to American households.”

After months of lobbying, Smit met with national Covid-19 supply coordinator Tim Manning on Jan. 6. Smit said Manning promised to work on relieving the NIOSH backlog and pushing for more advertising of N95 masks on sites like Facebook. The White House didn’t respond to requests for comment.

N95s are pricier than KN95s and cloth masks and can be difficult to find, so Americans are sourcing masks where they can find them. Amazon.com offers KN95s, a Chinese standard not independently verified by U.S. regulators. According to the CDC, about 60 percent of KN95s are fake.

Armbrust American, one AMMA manufacturer of N95s, shifted some production to KN95s because they were easier to sell.

U.S. manufacturers fault weak messaging from the CDC and the White House.

“There was a real overemphasis and kind of falling back on the vaccines, that that would be the silver bullet situation,” said Connor Knapp, a small New York-based mask maker and AMMA member. “I just didn’t see that being the case. I felt like it always required a multi-pronged approach.”