Californians may have to remain masked at work for several more months if any colleagues are unvaccinated, under new rules that state regulators were considering Thursday during a heated, marathon meeting.

The new rules would require employees, even those who have been vaccinated, to continue wearing masks indoors if they are around other workers who have not received the COVID vaccine. If everyone is vaccinated, though, the masks can come off.

The proposed mandate drew the ire of employers worried about having to police their workers’ vaccination status and employees sick of wearing masks — even as other workers applauded the rules or said they don’t go far enough to protect their safety.

The state Occupational Safety and Health Standards Board was still discussing the proposal late Thursday.

The new rules would add another layer of complexity to the state’s pandemic recovery as COVID cases decline, vaccination rates increase and society continues to reopen. They would force employers to pry into who has gotten a shot and who has not, yet leave unclear who would make sure the employers comply.

The Centers for Disease Control and Prevention last month declared it safe for fully vaccinated people to resume most activities, including eating indoors and gathering with friends, without wearing masks or social distancing. Gov. Gavin Newsom plans to fully reopen the state and drop most mask mandates June 15.

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But the state’s Division of Occupational Safety and Health, known as Cal/OSHA, isn’t ready to follow suit.

“The COVID-19 pandemic has had a devastating impact on workers, causing death, serious illness and in many cases, long term chronic illness,” Cal/OSHA deputy chief Eric Berg said, adding that while the situation has improved thanks to vaccines, it’s not yet safe to retire face masks, social distancing and other safety measures. “We cannot rely on vaccines alone to stop transmission of COVID-19 in the workplace,” he said.

The new rules would go into effect June 15 and last until early next year, though the agency has the option to repeal them sooner.

About 100 people called into the virtual meeting Thursday, arguing for and against the workplace mask mandate and other safety rules. Employer groups squared off against worker representatives, while some callers questioned the science behind face masks, called the mask mandate “tyrannical” and said the rules would further divide the state. Others worried the rules would single out unvaccinated workers and lead to workplace hostility and discrimination, as vaccinated workers blame unvaccinated colleagues for having to wear a mask.

Many callers urged Cal/OSHA to clarify how employers are supposed to verify their workers’ vaccination status. For example, what happens if an employee loses his or her vaccination card?

In Santa Clara County, employers already are dealing with some of those issues, Starting this week, the county required all employers to record the vaccination status of their workers or pay daily fines of up to $5,000 per violation. Employers don’t have to report this data to the county, so officials could not say how many businesses have complied so far. People can report violations at scccovidconcerns.org, and the county will follow up, a county representative wrote in an email.

The Cal/OSHA board first considered the new workplace rules last month, but postponed a vote to give regulators time to consider the latest CDC guidelines.

The agency made changes that “consider the latest scientific evidence,” Berg said. But workplaces present unique risk factors that the CDC guidelines don’t take into account, as workers spend long periods of time together, potentially allowing for prolonged exposure to COVID, Berg said.

Gina Ma, who works in a biotech lab in San Diego, urged Cal/OSHA to follow federal guidelines and toss the workplace mask rules.

“I am tired. I am tired of rebreathing my own CO2 for eight or more hours a day,” said Ma, who is vaccinated. “I am tired of hearing ‘wear a mask, save lives.’ I am tired of hearing about all of the great things I can do if I’m vaccinated, but only if I don’t live in the great state of California.”

Katie Hansen, senior legislative director for the California Restaurant Association, pointed out the irony that restaurant workers would have to wear a mask all day at work, then could return after their shift to the same restaurant maskless and order dinner.

But vaccination rates vary widely across the state, as do employers’ willingness to keep their workers safe from COVID, said David Barber, deputy chief counsel at the California School Employees Association. That’s why it’s crucial to continue enforcing masking rules in the workplace, he said.

“The pandemic is not over, and a deadly highly transmissible virus is still spreading in our communities,” Barber said.

Under the proposed rules, vaccinated workers would be allowed to take off their masks outside, while unvaccinated workers must keep them on if they can’t socially distance. Until July 31, employers could choose to enforce physical distancing and use safety partitions, or offer all unvaccinated employees N95 face masks. After July 31, they would be required to offer the N95 masks.

Many callers spoke out against the N95 mandate, worrying it would create a cost burden for employers already struggling financially, while also potentially creating a mask shortage similar to the one the country saw at the start of the pandemic — particularly as wildfire season looms, and the masks soon will be needed to protect Californians from smoke.

But Anne Katten of the California Rural Legal Assistance Foundation urged caution when loosening COVID safety rules.

“We’ve seen how premature rollbacks here and in other places in the past have resulted in infection surges,” she said, “and we need to prevent such occurrences.”