Could your cellphone’s electromagnetic field make you sick?

A California health activist says the Massachusetts Department of Public Health may be withholding information about possible health risks posed by cellphones and other wireless technologies.

Joel Moskowitz, director of the Center for Family and Community Health at the University of California Berkeley, said the state agency is refusing to release fact sheets about the health effects of electromagnetic fields, or EMF, that it began drafting two years ago.

“The higher-ups are very nervous about letting any of this information out to the public,” said Moskowitz. In California, Moskowitz fought a successful seven-year court battle to force that state to release guidelines for consumers on safe cellphone use.

Ann Scales, a spokeswoman for the Massachusetts agency, said the DPH plans to release the guidelines within six months.

Moskowitz and some other activists assert that exposure to EMF, the energy given off by countless modern devices, causes a variety of health problems, ranging from sleep loss to brain cancer. They say state and federal agencies have a duty to warn the public to reduce their exposure to EMF.

But both the World Health Organization and the US Centers for Disease Control and Prevention have said that evidence of health risks from EMF is inconclusive.

Moskowitz has joined forces with Cecelia Doucette, an Ashland resident and EMF activist who persuaded her town’s school district to set limits on student exposure to Wi-Fi radio waves. Doucette said she worked with Mass. DPH officials in 2016 to develop a fact sheet showing people how to shield themselves from Wi-Fi waves, as well as electromagnetic radiation from cellphones, cell towers, and high-voltage electric power lines.

But more than two years later, the fact sheet has yet to be released. “I don’t know why,” Doucette said. “They have not given me a reason aside from the fact that it is still under review.”

Moskowitz filed a public records request for the fact sheets with the Mass. DPH, but it was denied. Public records liaison Carolyn Wagner wrote that the document in question is exempt from the state’s disclosure law because it’s still in draft form.

Scales said that until the DPH releases its guidelines, consumers can find out about safe cellphone use from the National Institutes of Health’s National Cancer Institute, which has a Web page devoted to the subject.

Many scientists agree that EMF exposure may pose a health hazard. They’re especially concerned about cellphones, because of their position so close to the user’s head, thereby increasing the brain’s exposure to the phone’s electromagnetic field.

“The evidence that prolonged use of cellphones increases the risk of brain cancer is extremely strong,” said David Carpenter, professor of environmental health sciences at the University at Albany, State University of New York.

Carpenter pointed to recent large-scale studies in the United States and Italy that found that exposure to cellphone radio waves caused brain tumors in rats, as well as earlier studies that found evidence of increased cancer rates among heavy cellphone users.

“The degree of risk is debatable,” Carpenter said. “However, that there is a risk is really pretty clear.”

Richard Clapp, professor emeritus at Boston University’s School of Public Health, agreed. He recommended that consumers use wired earbuds to make calls instead of holding the handset to their ears.

“There’s good reason for being cautious,” Clapp said. “If you don’t have to expose yourself or you can reduce your exposure, do that.”

The World Health Organization states on its website that “to date there is no evidence to conclude that exposure to low level electromagnetic fields is harmful to human health.” Yet the WHO also lists electromagnetic fields as a “possible carcinogen.”

The controversy is likely to intensify in the years ahead with the deployment of next-generation 5G wireless systems, which operate at higher frequencies than today’s cellular systems and will require a far more transmitters.

“5G is going to put an antenna every several hundred yards in cities,” Moskowitz said. “The exposure will be substantial.”

The nation’s wireless companies plan to spend billions on 5G networks, and the Trump administration considers quick deployment of the technology a matter of national security. But Markowitz and other health activists want a moratorium on 5G technology pending more research on health risks.