Everyone working in the state health department's sixth-floor radiation lab in Baltimore knew it was only a matter of time before fallout from the damaged Fukushima Dai-ichi nuclear power plants in Japan finally reached Maryland.
But on March 23, when the signature of radioactive iodine 131 turned up in an air filter tested in one of the state health lab's gamma-ray counters, Abudureheman Abulimiti, a senior scientist in the lab, wasn't ready to believe it.
Although the radiation lab has been monitoring the state's air and water for decades, this was the first time its current employees — too new to recall the Chernobyl meltdown in 1986 — had seen a radioactive byproduct from a reactor accident.
"I was very surprised," said Abulimiti, who's been there about seven years. "I immediately got in contact with … my supervisor. Something was going on."
This was precisely what Maryland's far-flung radiation monitoring network was designed 30 years ago to do.
At least semiannually, and as often as every week for air and water, the multi-agency program gathers up samples of air, rain and drinking water, milk, wild-caught fish, vegetables, oysters, soil and sediments — mostly near the Peach Bottom and Calvert Cliffs nuclear power plants — to check for the first signs of leaked radiation.
The samples are then tested at the state public health lab in Baltimore, or by the Department of the Environment, to provide state officials with the information they need to protect the public's health.
And now, Abulimiti was looking at the first positive results.
Wary of an erroneous reading, he repeated the 17-hour gamma-ray count in another of the lab's five massive counters. The iodine 131 was still there. He also ran a clean filter through a count in the first gamma-ray counter, and found nothing. This was the real thing.
On Thursday, March 24, the word went out to top state officials. And on Sunday, the 27th, they made it public: A minute amount of radioactive iodine 131 had been detected by the state's monitoring system. They stressed that the amount was tiny — less than one picocurie — and far below the level that would raise public health concerns.
Dr. Clifford S. Mitchell, assistant director for environmental health at the state Department of Health and Mental Hygiene, said the find "is so far below any regulatory standards or public health kind of guideline that we're basically looking at the lowest possible edge of our ability to detect this."
The staff at the lab took some pride in that. The lab is one of just five in the nation equipped by the U.S. Food and Drug Administration as part of the Food Emergency Response Network. The FDA put it on standby after the Fukushima accident, ready to conduct "surge" radiological food testing if needed by the federal government.
The iodine 131 finding demonstrated the system's high sensitivity and an ability to quickly detect minute traces of radioactivity.
"It's extremely small," said Mirna Alpivar, who heads the radiation lab. The detectors measured it in femtocuries per cubic meter of air. A femtocurie is a thousandth of a picocurie. The federal limit for iodine 131 in food is 4,600 picocuries per kilogram or per liter.
Jonathan M. Links, director of Public Health Preparedness Programs at the Johns Hopkins Bloomberg School of Public Health, said radioactivity is a health concern because emissions of ionizing radiation such as gamma rays can damage DNA and cause cancers.
But the health effects are dose-dependent.
"If you look at the levels being detected, they're way below the levels of public health concern," he said. "It's simply that detection sensitivity is so good that even minute amounts can be picked up. The nice thing is we have a bit of an early-warning system."
And while the cancer risks are never zero, he said, at low doses they become vanishingly small compared with our "natural, spontaneous incidence of cancer."
Over our lifetimes, he said, "All of us in the U.S. carry a 40 percent risk of getting cancer, and a 20 percent risk of dying of cancer."
"We're all being exposed to radiation normally — cosmic rays, radioactivity in the soil, in building materials," Links said. "Even if it were right at the EPA action level of I-131 in drinking water, which it isn't … what we would pick up in terms of radiation dose is equivalent to one one-hundredth of what we're picking up every year from background radiation."
The I-131 caught in filters in Harford County was the first environmental sample in Maryland that has turned up any trace of fallout from the damaged Japanese reactors.
Very low levels of I-131 have turned up in water and milk on the West Coast, and in rainwater in Maryland, Massachusetts and Pennsylvania. While the rainwater levels exceed federal limits for drinking water, the EPA said those limits were calculated based on exposures over a 70-year lifetime. Preliminary milk testing was negative; quarterly milk tests will be done shortly, officials said.
The trail of the I-131 that turned up in a single Maryland air sample began 6,700 miles away in the damaged Fukushima reactors.
Links said I-131 is the most abundant of the radioactive elements forged in the reactors and released into the atmosphere. And that's probably why it turned up here first. Others include cesium 137 and strontium 90.
Iodine 131 is also the least troublesome of the three. With a half-life (the time needed for half the radioactivity to disappear) of just eight days, its radioactivity dissipates quickly, and if ingested it is cleared rapidly from the body. The half-lives of cesium 137 and strontium 90, by comparison, are both about 30 years.
After drifting with the atmospheric currents for a week or more, the I-131was captured in paper and carbon filters in an air sampler in Whiteford in northern Harford County.
Susan Gray, manager of the Power Plant Assessment Program in the state Department of the Environment, said the sampler is one of three in Maryland deployed downwind of the Peach Bottom power plant. There are four more near the Calvert Cliffs plant in Southern Maryland.
Mounted on posts and sheltered in louvered boxes the size of a doghouse, the air samplers use a small electric pump to draw a continuous stream of air through the filters.
The filters lie inside a blue plastic canister roughly the size and shape of a hockey puck. They are collected weekly by the Department of the Environment and brought to the state public health lab in Baltimore. One more is retrieved from an identical sampler on the roof of the state office building at 301 W. Preston St., nearer the state's population center, and next door to the lab.
In the lab's counting room, Abulimiti places each canister in a gamma-ray counter the size and shape of a garbage can. The sample sits atop a detector surrounded by 2,500 pounds of copper and lead to screen out natural background radiation.
For 17 hours the device quietly counts gamma rays emitted by the sample, and measures their intensity. The next morning, Abulimiti arrives to check the results on his computer screen.
The display is a vertical bar graph, and on March 23, Abulimiti spotted a fat red bar toward the left side of the graph where he had never seen one before. Its energy level identified it as iodine 131. It was unmistakable.
"Each radioactive element has a unique energy," said Alpivar. "It's like fingerprints." The counter reveals both which radioactive form of the element is there, and how much.
On Thursday, March 24, Abulimiti's findings were passed to the state's Ingestion Pathway Coordinating Committee — leaders and experts from Maryland's departments of health, environment, agriculture and emergency management who are charged with guiding the state's response to a radiological incident.
"This was the first time that most of us had had an actual measurement" to deal with, said Robert M. Summers, Maryland's acting secretary of the environment. The committee's previous meetings were mostly spent planning and drilling for the real thing. And when it came, it fell on the day of the committee's annual face-to-face meeting.
Three days later, after the committee's review, Summers and Maryland Health Secretary Joshua M. Sharfstein issued a news release announcing the low-level I-131 discovered in the Harford County air sample.
With new reports arriving from around the country, and more positive samples expected in Maryland in the coming weeks, the Ingestion Pathway Coordinating Committee now consults daily, Summers said. And it has ordered additional testing.
"As a precaution, we took additional samples of rainwater and raw water — water from streams and reservoirs," he said.
The stepped-up monitoring will continue, Summers said.
"We will remain vigilant, and we will update folks on a regular basis, if the situation changes, or simply to keep people informed," he said. "For the moment, I think that there should be no reason for concern."