PORTLAND, Maine—Power companies say new "smart meter" technology will cut energy use, benefit the environment and allow utilities to pinpoint problems during power outages more quickly.

But critics say the technology poses health risks and raises concerns about privacy and security.

Various studies say there's little or no evidence to suggest that exposure to radio frequencies from wireless network devices, such as the so-called smart meters, constitute health threats. But that's not stopping an outcry from smart-meter opponents who say additional investigation is warranted.

In Maine, dissenters have sent dozens of e-mails and letters to regulators and health officials just as the state's largest utility, Central Maine Power Co., begins its smart-meter rollout. A louder protest has come in California, where cities have passed moratoriums on the meters, demonstrators have blocked installation of the devices, and regulators have received thousands of complaints.

Smart meters have been linked to reports of dizziness, nausea, migraines, muscle spasms and insomnia, said Elisa Boxer-Cook, a vocal critic who wants CMP to stop installing the meters pending further study. Some people are concerned the meters might have more serious long-term effects, such as cancer, she said.

"The science is so unclear at this point that we don't want to blanket entire neighborhoods with radiation while scientists are debating this," said Boxer-Cook, of Scarborough.

But Dr. Dora Anne Mills, director of the Maine Center for Disease Control and Prevention, said based on the information she's seen, the meters aren't any more dangerous than wireless Internet routers and cordless telephones.

"Some of the analogies I've seen by opponents say it's like having a cell phone tower on the side of your house," Mills said. "It's more analogous to having a cell phone or a router or a cordless phone on the side of your house."

The new meters measure electricity used in homes and businesses, but instead of using gears and dials they use digital technology that records a wealth of information. CMP's meters contain small antennas that transmit data to larger antennas placed on utility poles and eventually on to CMP headquarters in Augusta.

The utility says the meters provide customers with real-time information on electrical usage and in time will allow power suppliers to offer consumers options for variable pricing or time-of-use rates.

Nationwide, smart meters have been installed in an estimated 10 million to 20 million homes, according to the Edison Electric Institute, a Washington, D.C., trade group that represents utilities. More than 65 million homes nationwide are expected to have them by 2020.

In California, one of the first states to see smart meters, a number of municipalities have enacted ordinances delaying their installation.

Two members of the state assembly have asked the California Council on Science & Technology - a nonpartisan, not-for-profit corporation that offers expert advice to the state government on science and technology-related policy issues - to determine whether FCC standards applied to smart meters are sufficient and if there are other possible health risks based on the cumulative impact of radiation exposure.

John Leopold, a member of the Santa Cruz County Board of Supervisors, said he's never seen an issue generate as many calls, letters and e-mails. The board last month unanimously approved a smart-meter moratorium through year's end.

"I'm concerned about what we don't know," Leopold said. "I haven't seen any scientific information that would lead me to believe there's a problem, but there are significant questions."

CMP, which last month began the two-year job of installing 620,000 meters, says smart meter signals resemble those of cell phones, cordless phones and walkie-talkies, except at lower frequency levels while transmitting for only a few minutes each day.

"We don't believe there's a risk," said CMP spokesman John Carroll.

The meters should also help the environment, he said. CMP estimates the meters will reduce about 2 million miles of driving a year by its meter readers, whose jobs are being eliminated.

But those assurances haven't been enough for dozens of people who have written to Maine Public Advocate Richard Davies, who represents consumers. In response, Davies asked Mills to look into the matter.

Most of the critics are concerned about health risks, Davies said, but a small number are also worried that the system might be penetrated by hackers who could access private information.

"People didn't know this was coming and once the news hit the newspaper, all these people who had health concerns about electromagnetic fields and other sources radiation all of the sudden are concerned that this isn't some distant problem - it's going to be on their house soon," he said.

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