Some East Bay residents were curious about a late summer low-flying helicopter survey of naturally-occurring radiation in the Bay Area, and asked Patch for more.
Here’s the initial story announcing the survey; and here’s Part 1 of our follow-up, where I described the frustratingly long process of trying to get more information from the federal agencies behind the effort.
I promised more on naturally-occurring radiation — a look into the what's, where's, and why’s. It does sound creepy, especially to those of us not well versed in planet, or planetary, chemistry.
To no surprise, radiation science isn't the stuff of brief web posts. But I’ll lay out some basics, with links and PDF’s to more.
For starters, “naturally-occurring” radiation may not be the best term for what the feds were surveying in Bay Area hills and dales. "Background” radiation is probably more accurate, according to the scientists I interviewed.
Radiation is part of everyday life
“My main message to you is that, yes, there are several natural and man-made sources of radiation in the everyday environment,” wrote Cary Zeitlin, Ph.D., a high energy physicist at the nonprofit Southwest Research Institute in Texas, who lives in the East Bay. Among other things, Zeitlin is known for his work investigating radiation on Mars for NASA, working with the Mars Odyssey mission.
Zeitlin was one of a few experts who emailed me, or commented, after my first post. He went on:
“Cosmic rays give us all a small dose of radiation, which is increased by living at high altitudes, flying in an airplane, etc. Medical and dental x-rays contribute, and in some parts of the world, naturally-occurring radon gas is present.
"Beyond that, our bodies are all very slightly radioactive, due mainly to potassium-40 in bones and teeth. And there is a tiny (really tiny) contribution to the annual dose as a residual effect of above-ground A-bomb testing in the 1950's."
Many sources - terrestrial, cosmic, manufactured
Kathy Shingleton, a radiation safety leader at Lawrence Livermore National Lab (LLNL), elaborated that background radiation, mostly in very low levels, is present everywhere on earth, as it's an element of the earth's crust (terrestrial sources), showing up in soil, water, rock, and air, and of the cosmos (cosmic or extraterrestrial sources), showing up in the skies.
“The whole earth is radioactive,” Shingleton said. "It was more so one to two million years ago, radioactive material is decreasing, but we’ve lived in a radioactive environment since the Big Bang.”
Manufactured sources make “very, very small contributions” to background radiation, Shingleton said. This includes radiation from medical procedures, weapons, power plants, some ship and airplane parts, watch illumination and other uses.
See PDF's to the right with details on background radiation from the Health Physics Society.
Radon is a concern; Bay Area not hot spot
Assessing the health risks of exposure to background radiation is complicated and controversial, but radon poses the greatest concern, depending on where you live, Shingleton and Zeitlin agree.
“Health effects from naturally-occurring radiation are generally so small as to be unmmeasurable, with the exception of radon," Zeitlin said.
Radon is a radioactive gas byproduct of decaying uranium, and to a lesser degree thorium (heavy metals in the earth's crust), that's present on the earth's surface in widely varying degrees, depending mainly on the surface rock. Radon can get trapped and concentrated in homes and other structures located in areas with higher levels, resulting in potentially dangerous exposures.
In the U.S., the Environmental Protection Agency (EPA) monitors ground radon, including issuing guidelines for residents and builders. Well-ventilated buildings pose less risk. Check the EPA's radon webpages for more information. Most states, including California, have a radon coordinator.
The Bay Area, and most of California, isn’t a radon hot zone, or a region with levels of concern. This doesn’t mean there isn’t any radon in our terrain, but relatively little compared to known hot spots in the midwest and eastern parts of the country, Shingleton said. It's not considered a health risk here. See the EPA’s radon map.
About those low-flying radiation detectors
So, how does this tie into those buzzing helicopters?
Aerial surveys of background radiation have been done intermittently in the U.S. for years, Shingelton said. Sometimes they're collecting data; sometimes testing equipment, or both.
“I learned that the Aug surveys were done as part of a research and development project to obtain baseline aerial measurement data over topograhpically diverse terrains (e.g., hilly, urban, water), which the Bay Area is rich in,” Shingleton said, adding that a Berkeley-based scientist is involved in the work.
“The surveys were not done in response to any particular threat or concern."
“On a more general note," Shingleton continued, "The ability to make aerial measurements of background radiation is a very useful tool, and communities/states are recognizing the value of establishing background radiation levels in their communities BEFORE an incident occurs, as it can dramatically improve detection criteria, clean-up strategies, and public confidence should a radiological event occur."
"Following any radiological incident, there is tremendous pressure to return the area to its 'pre-incident' condition. If the 'natural background levels' are not known prior to the incident, there will never be public consensus of when that endpoint is achieved," Shingleton said.