Radon gas infiltrates mansion

May 14, 1995|By Mike Klingaman | Mike Klingaman,Sun Staff Writer

Hampton Mansion, the 18th-century centerpiece of a National Historic Site in Towson, has a radioactive intruder in the basement.

The invisible invader is radon, the cancer-causing gas that is as old as the hills -- and somewhat mysterious as to how big a threat it is.

Colorless and odorless, radon seeps into buildings from the soil. Concentrations usually reach a peak in the winter because closed windows reduce ventilation.

In February, one room in the mansion basement had a reading of 11.6 picocuries per liter of air, well above the Environmental Protection Agency's risk point of 4 picocuries for dwellings.

(A picocurie is a measurement of radioactivity.)

Ten National Park Service employees work in basement offices but have been advised that radon levels are not high enough to harm them -- and are of no consequence to the 50,000 people who tour the mansion each year.

The park service has spent about $20,000 trying to seal floors and walls in the basement of the 1790 mansion on Hampton Lane, north of the Baltimore Beltway.

And the battle against radon is causing consternation.

"When the readings pass 10, you wonder, 'What's going on here?' " says Greg McGuire, maintenance chief at Hampton.

"I've asked the staff to keep things in perspective," says John Hanley, the federal environmental consultant in charge of corrective work. "They're in and out of the basement all the time; they are not at great risk." Bess Sherman, superintendent at Hampton, agrees.

"I've read all the research and I draw this conclusion: It's not that bad, and I don't stay here 24 hours a day," Ms. Sherman says.

The National Historic Site lies in postal zone 21204, and 40 percent of the 402 dwellings tested in that area were at or above the risk point of 4 picocuries, according to tabulations by the EPA.

Since the mid-1980s, the agency has collected the results of more than 75,000 radon tests in Maryland, showing that Carroll County has the worst problem in the Baltimore metropolitan area; 67 percent of the 4,015 dwellings tested in Carroll were at or above 4 picocuries, and the highest individual reading was 883.

Howard County was next highest, with 49 percent of the homes tested at or above the risk point, and a top reading of 365.

In Harford County, the figures were 36 percent and 1,006; Baltimore County, 33.8 percent and 270; Anne Arundel County, 23.3 percent and 313; and Baltimore City, 13.3 percent and a high of 199.

At Hampton, the park service has replaced old earthen floors, covered picturesque stone walls and installed a ventilation system.

But the intruder remained shifty; picocurie levels in some office areas plunged but increased elsewhere.

Officials were irked that one of the highest readings came in February -- after most of the repairs had been made. The #F findings triggered further testing.

Those results, due this month, "will determine our plan of attack," Mr. McGuire says.

Leon Rachuba, a health physicist with the Maryland Department of the Environment, notes that radon concentrations in any building can vary greatly from season to season.

And a high of 11.6 picocuries in the basement is no cause for restricting tourist traffic in the mansion itself, he says.

The federal government ranks radon as a Class A carcinogen, along with secondhand tobacco smoke, benzene and asbestos.

About 150,000 deaths from lung cancer occur each year in the United States, and perhaps 10 percent are caused by radon, the EPA estimates.

The gas causes more deaths than fires and drowning combined, but fewer than auto accidents triggered by drunken drivers, the agency says.

Its radon risk assessments are based on a theoretical exposure of 18 hours a day for a lifetime.

Though environmental scientists agree that radon is a human carcinogen, some researchers say the EPA estimate of deaths is too high.

Those critics note that the EPA's annual total is not based on data about homeowners but is extrapolated from studies of miners.

Nonetheless, most homes in the United States are thought to have some radon, which comes from the natural breakdown of microscopic amounts of uranium in soil, rock and subterranean water.

The gas releases bursts of energy that can damage the genetic coding of lung cells and cause cancer to develop. No other cancer is linked to radon.

Igneous bedrock and related soils are leading sources of the gas, and much of Central Maryland has that composition.

This "radon belt," known to geologists as the Piedmont, is bordered by Interstate 95 on the east and the Blue Ridge Mountains to the west. The mountains bisect the state near Hagerstown. Because so many geologic and structural factors affect the movement of radon, there is no way to predict which buildings have high concentrations. Houses on the same block can have vastly different readings.

For homeowners, testing is do-it-yourself, using kits available at hardware stores. These simple devices are placed in the living space closest to the ground. (For example, a basement family room should be tested, but not a seldom-used crawl space underneath.)

The Maryland Department of the Environment has a toll-free information line, (800) 872-3666, and keeps a list of contractors able to do major radon-venting work.

The EPA recommends follow-up testing before any remedial work is done; if the initial test with a charcoal canister (around $10) shows 4 picocuries or more, do a second short-term test.

If the level stays above 4, do a long-term test lasting at least 90 days, using an "alpha-track" or "electret" type of detector, costing around $30. Only this type of test can confirm whether a home actually has a serious problem.

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