AUGUSTA – The senator who will head the Natural Resources Committee has come up with a new approach to keeping highly toxic mercury from contaminating the environment: a thermometer trade-in program.

Sen. John Martin, D-Eagle Lake, envisions a program in which consumers would take their old household thermometers containing mercury to a drugstore and trade them in for environmentally friendly models.

Details are still being refined, but Martin said Tuesday he wants the trade-ins to come at no cost to consumers and minimal, if any, cost to the state.

“My bottom line,” said Martin, “is to get them out of circulation.”

His bill is the latest in a series of steps the Legislature has taken to prevent mercury pollution. The Natural Resources Council of Maine said it is pleased to see the newest proposal.

Thermometers are a significant contributor to mercury pollution in the environment, a Department of Environmental Protection official said. Broken fluorescent light tubes are another major mercury source.

In November, the city of Boston banned the sale of mercury-containing thermometers. In June, New Hampshire became the first state to adopt such a prohibition. Cities across the country, such as San Francisco, Ann Arbor, Mich., and Duluth, Minn., also enacted bans last year.

Other cities, such as Palo Alto, Calif., have trade-in programs where people are offered coupons toward the purchase of nonmercury thermometers.

The U.S. Environmental Protection Agency estimates that 17 tons of mercury from thermometers ends up in the nation’s landfills each year.

Mercury damages the liver and the brain while eroding the nervous system. Unborn and young children and the elderly are the most vulnerable. Mercury is especially dangerous because it accumulates in increasing amounts as it rises through the food chain.

Martin said his bill stems in part from past work the Natural Resources Committee has done on mercury pollution, such as legislation dealing with mercury pollution from incinerators.

Martin said people would be surprised to learn how much mercury finds its way into the environment from thermometers from home medicine cabinets that are broken or discarded. Only a tiny amount, said Martin as he pinched the tip of his finger for emphasis, can destroy a whole lake.

The average mercury thermometer to register fevers contains a half-gram of the substance, said David Lennett, director of DEP’s Bureau of Remediation and Waste Management. The DEP estimates that 155 pounds of mercury per year are deposited in Maine’s environment.

Coal-fired utilities and incinerators release the heavy metal into the air. When it falls as rain, it is absorbed by microorganisms in lakes and ponds and gets passed through the food chain to fish, birds and humans.

The DEP is revising its water quality standard for mercury. New standards could set limits at the low single numbers per trillion parts, said Lennett, although even harsher standards have been discussed.

Last year, the Legislature passed a bill requiring the labeling of a number of devices and consumer items containing mercury, but Martin’s bill goes beyond the requirements of the new law.

Maine also joined Vermont, Connecticut and Minnesota in the small group of states that have banned the disposal of fluorescent lamps in landfills.

The state also issues warnings on the risks of eating certain species of fish that may contain mercury.

Meanwhile, a coalition of environmental groups is trying to stop the shipment of 130 tons of mercury from the closed HoltraChem Manufacturing Co. plant in Orrington. The groups contend that the mercury, which is destined for India, will eventually end up in the air and be blown back to Maine.