SACRAMENTO — Newly released public records show that California public health officials worked for five years on a set of guidelines to warn the public about the potential dangers of cell phones, revising their work 27 times with updated research before abandoning the efforts without ever making their concerns public until ordered by a judge.

The 27 versions of the guidelines, obtained by The Chronicle, show that California health officials deleted a section that warned state employees with work-issued cell phones about the potential increased risk for brain cancer from use of the devices over time. The final version of the guidelines was a broad warning to the public about exposure to electromagnetic fields emitted by cell phones. It included a list of best practices to minimize exposure.

Joel Moskowitz, a public health researcher at UC Berkeley who sued the state to force the release of the records, said state officials should never have withheld the warnings from the public. Lawyers for the state had argued in court that release of the warnings could cause unnecessary panic.

“It would have to be purely political to deny distributing this,” Moskowitz said. “Science supports this.”

Sacramento County Superior Court Judge Shelleyanne Chang ordered the state in March to turn over the final version of the guidelines from 2014. Last week, as part of the lawsuit, the judge forced California health officials to turn over all the previous versions of the guidelines it had kept secret.

It’s unclear what debate went on inside the California Public Health Department over the guidelines — and whether there was any influence from outside the department.

The Chronicle submitted a public records request to the health department in March, asking for emails or documents related to why the cell phone guidelines were never approved to be made public — and to see whether there was any outside influence. The department refused to release records, saying those that existed were protected by attorney-client privilege.

The little information that is known about the state’s efforts to create and then abandon cell phone guidelines can be gleaned from Moskowitz’s lawsuit and the newly released documents.

The first version of the guidelines, from 2009, said recent studies of cell phone and cordless phone use “suggest that after 10 years of heavy use there is an increased risk of malignant brain cancer and a kind of benign tumor in the inner ear, particularly on the side of the head where these phones are usually placed.” The state department reviewing the material, the Division of Environmental and Occupational Disease Control, wrote that following its own “unpublished meta-analysis,” it agreed with the conclusions of the studies. Similar language about long-term effects was included in the later versions, but not the part about a consensus of study findings by the division.

The first version also included this language, which was later removed: “Although most cell phone and cordless phone heavy users would not get brain cancer, the number of brain cancer patients coming to hospitals would increase and would represent a significant cost to society in suffering, medical costs and economic costs that one would want to avoid.”

Additionally, the first version noted that the lifetime risk of getting brain cancer is low, but that longtime heavy use of cell phones and cordless phones is enough to be of “regulatory concern.” That “regulatory concern” was removed in the later versions.

The early document also included the section of state employees, which was deleted. It detailed how state government and its employees could lower the risk of exposure, such as reducing the time workers were required to be on their cell phones, avoiding purchasing cordless phones for office use and ensuring that employees have headsets.

The first version also warned: “Do not allow children to use a cell phone, except for emergencies.” The final version said, “Parents may want to limit their child’s cell phone use to texting, important calls and emergencies.”

“I want to know why this was suppressed,” Moskowitz said, referring to information he feels parents should be aware of.

The California Department of Public Health declined an interview request, releasing only written statements.

“The draft cell phone guidelines attempted to characterize the complex science around radiofrequency electromagnetic field (EMF) and provide options for people who want to reduce their exposure,” the statement read.

The health department told The Chronicle in March that it abandoned the guidelines because the federal Centers for Disease Control and Prevention issued national guidance on the same subject in 2014. But, even those national guidelines were the subject of controversy.

CDC’s updated guidelines in 2014 read “we recommend caution in cell phone use,” but that language was deleted weeks later.

A New York Times investigation last year, examining more than 500 pages of internal CDC records, found the agency’s new language had been worked on for three years, but soon after it was published, officials grew concerned that it was being mistaken as a policy change. The language was then changed again in 2014 to say: “Some organizations recommend caution in cell phone use. More research is needed before we know if using cell phones causes health effects.”

Moskowitz said he hopes the state will decide to adopt and post the guidelines its own department created.

“It seems to me better late than never to notify the public,” Moskowitz said. “The public has a right to this information paid for with their tax dollars.”

The statement from the California Department of Public Health said there are no plans to post the guidelines on its website.

Melody Gutierrez is a San Francisco Chronicle staff writer. Email: mgutierrez@sfchronicle.com Twitter: @MelodyGutierrez

Guidelines on safe mobile usage

Increase the distance between you and your cell phone by:

Using the speaker phone.

Sending text messages.

Use a headset, and carry your phone away from your body. EMFs from wireless (Bluetooth) and wired headsets are usually weaker than those from a cell phone.

Keep your phone away from your body. A cell phone that is on can emit EMFs even when it is not being used.

Do not sleep with your cell phone near you or carry it in a pocket or directly on your body unless the phone is turned off.

Keep cell phone calls short, even when using a wireless or wired headset.

Take off your headset when you’re not on a call. Wireless and wired headsets emit EMFs even when you are not using your phone.

Do not rely on devices that claim to shield or neutralize EMFs from cell phones. These devices have not been shown to reduce exposures.