Renovations are ongoing inside Ann Arbor's city hall, where high radon levels were recorded in the basement where police officers worked for many years until recently. The new police-courts building, at right, now houses the department's 124 sworn officers.

Ryan J. Stanton | AnnArbor.com

"The most important message that we have is for everyone to test their home for radon," said Angela Parsons, an environmental educator and radon expert with Washtenaw County Public Health. "Especially in this area, we have a rather high concentration of radon. Any home could have it — if it's new, old, big, small, has a basement, doesn't have a basement."

Parsons estimates about 40 percent of homes in the county have radon levels above 4 picocuries per liter of air, the level at which the U.S. Environmental Protection Agency recommends taking remedial action to avoid the risk of lung cancer.

This map shows Washtenaw County is a Zone 1 (red) area, meaning it has the highest potential for radon above the EPA action level of 4 pCi/L. Zone 2 (orange) means moderate potential and Zone 3 (yellow) means low potential.

It can enter homes through cracks in foundations, sump pump crocks, crawl spaces and other openings. It's the second leading cause of lung cancer in the United States, responsible for an estimated 21,000 deaths per year, according to the EPA.

Kurt Hudgins, president of Ann Arbor-based Protech Environmental Services, does radon testing and mitigation work all over Washtenaw County and Southeast Michigan.

"It's a pretty prevalent problem in the area that we're in," he agreed. "Radon comes from uranium decay in the soil and radon is actually one of the byproducts, so in the southern counties — Washtenaw, Lenawee, Hillsdale — all these counties definitely have higher issues with occurrence than when you get farther east and farther north."

Parsons said the county has home test kits available for $10, and the county keeps a database of results. In Ann Arbor's 48104 zip code, 533 tests conducted since the 1990s came back with an average reading of 5 pCi/L, while the highest was 44.9 pCi/L. Countywide, the highest reading recorded was 177.2 pCi/L, which Parsons called "pretty significant."

"And there's also been one that's 176 and 134," she said. "It's rare to get one over 100, but it wouldn't shock me to get one that high."

Tests conducted in the basement of Ann Arbor's city hall in recent years showed radon levels seven times the EPA action level, according to records obtained by AnnArbor.com.

Parsons was brought in by the city to educate employees about radon in May 2009, along with Kim Kearfott, a professor of nuclear engineering and radiology at the University of Michigan. They conducted two training sessions for a total of 125 city employees.

Parsons declined to comment on whether the levels inside city hall were safe, saying only, "There is no safe level of exposure to radon, according to the EPA."

Tests conducted by the Michigan Occupational Safety and Health Administration from March 11-16, 2009, showed radon levels ranging from 21.9 to 28.8 pCi/L in the city hall basement.

According to the EPA, if 1,000 people who never smoked were exposed to 20 pCi/L over a lifetime, about 36 could get lung cancer. The number goes up to 260 for smokers. Under the naturally occurring outdoor radon rate of 0.4 pCi/L, about 3 people could get lung cancer, the EPA estimates.

Despite the high readings, MIOSHA's inspection — which came in response to a complaint from the police officers union — never resulted in a citation.

Elaine Clapp, safety and health manager with MIOSHA, said the state agency follows U.S. Occupational Safety and Health Administration regulations, which set the maximum permissible workplace exposure limit at 100 pCi/L for 40 hours over seven consecutive work days. Unless a test done by MIOSHA showed levels above that, no citation can be issued.

"We can't enforce EPA levels," Clapp said, acknowledging OSHA has different standards. "I don't set those standards and I didn't create the science behind it. All we do is enforce the regulations. Whatever their rationale for doing it, we have to enforce their rationale."

Clapp said the thinking is that employees aren't exposed to the radon levels during their work shift in as long a duration as they would be if the same levels were in their home, so higher levels are tolerated by OSHA in the workplace.

Hudgins said most commercial buildings with modern-day heating and cooling systems have enough airflow to pressurize the building enough so that radon infiltration is not an issue.

"Or if there is a radon issue, many times balancing those systems can correct the issue," he said. "If it's not an adequate enough system, then sometimes you have to go with an active mitigation system like soil depressurization to reduce the levels."

A look at radon levels throughout the United States.

"They can get test kits through us, or they can get them through the county health department," he said. "They're typically around $10 to test their house and find out if they have an issue. That's the first and foremost step to take. It's a very easy test to do and very inexpensive."

Hudgins agreed it doesn't matter if the home has a basement or not. The concern, he said, is the level of the home that's in contact with the soil.

Parsons said tests are available from the county at its offices at 705 N. Zeeb Road or by calling 734-222-3869.

"That short-term test is a good screening device to see kind of where you are in the grand scheme of radon," Parsons said. "Because the levels do fluctuate due to a variety of reasons: weather patterns, different times of year, the operation of the heating and cooling system."

Because radon levels can fluctuate, Kearfott said, people shouldn't get too alarmed if a short-term test done over only a handful of days shows readings above the EPA action level. That just means more testing needs to be done, Kearfott said, but she still recommends following EPA guidelines. And if high levels persist, then there's a real concern.

Kearfott said the only known risk of radon exposure is lung cancer.

"And there's a latency period for it showing up," she said. "So you wouldn't see it really manifest for a while and you would have to be exposed to it for some time even at the higher levels. So for short time periods, you could be exposed to 100 and it's not an issue."

So what are some of the rules regarding radon?

"There are very limited regulations," Parsons said. "For the state of Michigan, if you know that you have radon or if you've done a radon test and you're selling your home, you need to list it on the seller's disclosure statement. And also homes that are used for child care need to be tested and have acceptable levels of radon, less than 4 pCi/L."

Because Washtenaw County is considered a "Zone 1" county, which means it has a higher likelihood of radon, new construction here must be done using radon-resistant techniques.

"And essentially what that means is when a new home is being built or an addition is being placed onto a home, they incorporate a radon mitigation system into that construction," Parsons said. "And it's a really good idea and it's really smart to do because it's much less expensive."

Parsons said the only other regulation she's aware of is Ann Arbor's housing code, which states that a basement can't be used as habitable space unless testing done by an independent third party shows acceptable levels of radon.

Mayor John Hieftje, who used to work in residential real estate, said he's very familiar with the issue because homes are often tested for radon when they're bought and sold.

"There's radon everywhere. Most people have it in their homes to some degree," he said. "A lot of places in Washtenaw County are way over — like 30 is probably not an unusual reading. In a lot of reports I've seen in my previous business, there would be spikes that would jump up pretty high. But it was the average over time you want to be below the action level of 4."

Ryan J. Stanton covers government and politics for AnnArbor.com. Reach him at ryanstanton@annarbor.com or 734-623-2529. You also can follow him on Twitter or subscribe to AnnArbor.com's e-mail newsletters.