Radiation exposure in the United States: Ask the expert

Mar 30, 2011

If you have questions about how radiation exposure might be affecting U.S. citizens, then we've got answers. Medical physicist and radiation expert Jonathan Links will be here to address your radiation concerns.

Hi Folks: Jon Links here. We'll be starting in a minute!

The information coming from government officials is unclear. One day it sounds like they have it under control and the next day it seems there is no control. See question on Quora

I sympathize with the frustration of getting incomplete, contradictory, and ever-changing information; I don't have any special inside track, and see what you see, with perhaps a bit of extra state and federal intel. Chernobyl is the worst nuclear power accident in history. That event has led to 6000 thyroid cancer deaths, and a significant population displacement and economic impact, but not world-wide destruction. The second worst accident, Three Mile Island, led to no identifiable deaths.

How can TEPCO dispose of the radioactive water at the Fukushima Dai-ichi plant? See question on Quora

Disposal will ultimately depend on which radionuclides are in the water, and in what quantities. TEPCO may need to store the water on-site, or release it only if it can be put in a large enough volume of dilution water ... such as the sea.

Most of the articles I have read about radiation exposure have said basically we are all exposed to small amounts of radiation every day and even if the accident causes more exposure this would raise our risk of cancer by 5%. My question is if someone either inhales or consumes even a small amount of radioactive strotrium or cesium wouldn't this increase their risk of cancer by much much more than 5%? They would now receive a continuous, imminent dose a radiation for the rest of their life. Is there any evidence of this following Chernobyl? Thanks

We are indeed exposed to ionizing radiation every day; we receive an annual background dose of around 300-350 millirem, from cosmic rays, radioactivity in soil, and even naturally-occurring radioactivity in our own bodies. Any increase in cancer risk depends on radiation dose - increasing dose = increasing risk. So, giving a risk # like 5% has no meaning per se.

Detectable, but undisclosed concentrations of fission byproducts, including Cs137, have already been measured in California's rain water and air. How do measured levels of decay count-per-minute translate into airborne concentrations that residents are breathing? What are the pharmacodynamics of inhaled and ingested Cs137 particles? See question on Quora

In fact, the State of Maryland has been able to detect I-131 in air and rainwater. BUT it's important to appreciate just how good/sensitive our radiation detectors are these days, and detecting or measuring per se is not the same thing as public health risk. With respect to "units," 1 Bequerrel = 1 decay per second; 1 Curie = 3.7 10^10 decays per sec.

I-131 and Cs-137 particles can be inhaled or ingested. Their distribution in the body and clearance from it (toxicokinetics) depends on the specific physico-chemical form; their effects on the body (toxicodynamics) depends on the kinetics and doses. I-131 is mainly a thyroid threat; Cs-137 can have a broader distribution in the body.

Iodine-131 has been detected in Florida and has been attributed to the Japanese reactor releases. It was detected at an extremely low level comparable to the levels of this isotope generated by solar radiation. If further significant releases in Japan occur, are there steps that U.S. citizens should take to reduce risk of exposure, if so, what are they?

IMHO, this is a case of very sensitive detection capability causing unnecessary alarm ... at least for now. However, were the levels to rise to a point of public health risk, which is not expected to actually happen, then KI (or even table salt as a source of iodine) may become recommended, especially for children.

Given the stories of radioactivity now circulating the globe, and recently being detected in the rainwater on the east coast of the US, exactly how long will the water remain radioactive? When exactly will that rainwater lose all radioactivity?

Radioactive decay occurs monoexponentially with time. A monoexponential curve never, in theory, goes to zero. So, the real question is when will the levels become so low as to be indistinguishable from background? That could actually take years in some cases, with radionuclides with decades-long half-lives (e.g., Cs-137) ... depending on environmental clearance.

Should we be concerned with radiation exposure in the western Unites States in the even of a melt down?

Maybe (there are too many uncertainties, including the quantities released and prevailing wind at the time, to answer 'yes' or 'no') ... but such a catastrophic meltdown is no longer anticipated.

Who is responsible for telling us if radiation levels in our city are high? Once high levels are detected, won't it be too late to do anything to protect ourselves if the radiation is airborne? If high levels are present, how long does the danger last?

EPA at the Federal level, and each state's health department, environment and/or natural resources department, and each large city's agencies monitor air and water on a multi-times-per-day basis routinely. This monitoring should pick up any increases ... which is in fact how we know about the elevated levels in some states. Of importance, those levels are FAR below what would constitute a public health risk, indicating the monitoring is so sensitive that we'd have plenty of warning.

I have been researching and planning a trip to China in late spring. Considering their close proximity, I am concerned about the possible effects of radiation in China from the nuclear plant problems in Japan. Should I put my trip off until the Fall or next year? Thanks for any information you can give me. GJ

This is a personal decision based on risk vs benefit. I can tell you that I literally just returned from China myself, having been there for 9 days ... and it was well worth it!

How does the radiation from the nuclear plant spread? Does it freely travel through all material including air, water, earth? What is the least and most resistance material to nuclear radiation? What is the affect of radiation over the human body? What is the most affected part of the body? Thank you!

Radioactive releases would start in air (and certainly air is the primary vector for transport over large geographic distances). Some radioactivity would settle out ("fallout") onto the ground, getting into soil, plants, and animals.

"Resistant" materials are those that are unaffected by radiation. In our bodies, the skin is relatively radiation-resistant. "Shielding" materials, which I'm guessing is the real question, are those that absorb radiation (e.g., lead for x-rays and gamma-rays).

The distribution of radioactivity and the irradiation pattern depend on the sources of exposure. This also then determines the most at-risk organ or part of the body.

The RadNet stations throughout California that are used to see if there is fallout from Japan are only measuring Air particulates. But what if radioactive materials come across the pacific in higher layers and the only way we come in contact with them is through precipitation and deposition in the soil, etc? See question on Quora

The Feds and most states are not only looking at air, but at rainwater, surface water, and soil.

Hiroshima and Nagasaki suffered devastating nuclear explosions in 1945 and they have been rebuilt. Chernobyl suffered a meltdown in 1986 and may not be habitable for thousands of years. What is the difference? See question on Quora

The difference is a combination of which radionuclides, in what amounts, and economic considerations.

What can informed citizens do to reduce the quantity of food they consume that contains Fukushima radiation? Will ocean fish contain Fukushima radiation for years, even centuries to come (considering half lives of some elements)? Aren't we already eating food containing Chernobyl, Pacific Nuclear test bombs, and 3 Mile Island radiation (to name just a few man made sources)?

The challenge is that radioactivity (from a bunch of natural sources) is already all around us ... and in our bodies. I don't find it helpful to think in terms of "zero," so I don't find it helpful to think in binary (yes/no) terms of contaminated or not. Right now, there's no evidence that we are eating anything with significant (as opposed to "measureable") quantities of any radionuclide.

In search of answers of how to protect my self and my family from radiation I came to understand that there are different types if radiation and ones are more harmfull than others. For instance Gama radiation, the one most likely to come from atomic plant fuel spills and nuclear fallout is the most penetrating and most harmful to living organisms at the cellular level including DNA reproduction , I came across a couple of articles that suggest that certain vitamins can be used by body cells to protect or repair damage from exposure to Gama radiation. In the articles they mention Vitamin C , A, D ,E Bcomplex, Betacarotene etc. Ones help with protection to exposure and others with repair from damage already done by exposure. Can you elaborate, confirm or deny this allegations. Can you Explain what are your recommendations in terms what we can do and what Vitamin Supply we should have available to deal with radiation issues. Thanks

I don't think it's helpful to consider taking anything (vitamins, KI) at this time specifically in the context of potential ionzing radiation exposure from Japan. I personally take a daily multi-vitamin anyway, and am certainly interested in any and all free radical scavengers.

With respect to the dangers of different ionzing radiations, it depends on whether the source of the radiation is external to the body (in which case x-rays and gamma-rays, because they're so penetrating, pose the greatest risks) or internal contamination (in which case alphas and betas, because they deposit their energy over very short distances and are already starting out inside the body, pose the greatest risks).

Apparently, people in China are hoarding salt for protection against radiation. Is there any way this could work at all? Would one die of salt poisoning before acquiring a useful dose? See question on Quora

It all depends on how much iodine has been added; it's not bad advice.

The Fox News "science team" referred to a controversial report that radiation is actually good for your health. Who is right on this question? Here is the Fox News segment.

Who is right? Ann Coulter or Science? See question on Quora

There's a controversial concept called hormesis, from the Greek for "to excite," that proposes very small doses of toxicants stimulate the body's repair mechanisms ... leading to the repair of the small amount of damage caused by the toxicant AND any other damage lying around.

Did we get any radiation on the Saturday snow showers?

Don't know where you live, but if there's radioactivity in the air, some of it will indeed be captured in rain or snow and settle out.

I have noticed a proliferation of measurement units in the coverage of radiation leaks from the reactors in Japan: millisieverts, curies, and one named for another French person that begins with a "b." Can you help me sort all this out? Why so many?

Radioactivity (decays per unit time) is measured in Bequerrel (the International System unit) or Curie (the traditional unit).

Radiation dose is measured in Sievert (the SI unit) or rem (the traditional unit).

Most environmental regulation is in terms of radioactivity; risk depends on dose.

Question from the west coast - I read one day that part of the reason there were no reportings of radiation was due to most of the EPA monitoring stations on the west coast were no longer functional or had been defunded or turned off. And then I heard no more about that. Is it true? Have they been reactivated? What kind of monitoring is actually going on?   How strong is Obam's desire that "nothing is wrong" that he and many are in denial---to the people's possible detriment?

I can't comment on the RADNet issue ... but as a native San Franciscan, I can't imagine California hiding anything!

If someone ingests plutonium atoms (or other radioactive elements with long half lives), does that mean that person will be exposed to a continuous dose of radiation basically for the rest of their (short?) life?

NO - because in addition to the physical decay (leading to the long half-life) there is biological clearance - a biological half-life ... that is much shorter!

Can you relate the level of exposure expected to be in the average US citizen to exposures to which we are more accustomed? Like a dental xray?

The average person in this country is going to have no measureable exposure. For reference, we all pick up 300-350 millirem each year from background sources; a chest x-ray is 10-20 millirem; and the EPA regulatory limit for beta emitters in water would lead to an annual dose of only 4 millirem.

I worked at 9/11 in NY and am one of the casualties with lung issues. At the time, the government sent medical teams around assuring us there was nothing to be concerned about in the particulates in the air. Since then, I'm not inclined to take government announcements or media at face value. Is there a source for monitoring current and predicted radiation levels that we in California can refer to? And is there a resource for accurate, honest, reporting of when to be concerned. Learning the danger after the fact of exposure to avoid political issues or prevent panic, isn't really all that helpful.

I understand and sympathize! EPA RADNet data is open-access on the web. I don't know what California's Health Dept has on its website, but I'm betting they do have the data available.

There are reports (as of 28 March 2011) of radiation at these levels in some areas outside the Fukushima reactors. How long would exposure need to be before a person was in serious trouble? See question on Quora

Fundamentally, the risk depends on the total accumulated dose, so the way to think about risk is dose rate x total exposure time. The dose rates beyond the perimeters of the plant fall off pretty dramatically (according to news reports).

Should we be limiting our time outdoors here in the U.S. if we're breathing iodine-131 as has been detected? I know the concentration levels have been described as harmless, but isn't the effect cumulative?

The effect (increased risk of thyroid cancer) indeed depends on cumulative dose, but the measured (as publicly disseminated) levels are so incredibly low that I don't think any change in daily behavior is warranted ... and I certainly haven't in any way changed my behavior.

Do we need to worry about local fishing out here? Is the whole ocean going to get irradiated (exaggeration, of course, but you get the point)? Is it pointless to be worried because there's nothing we can do anyway?

I wouldn't worry yet. Whether I'd ever worry will ultimately depend on what gets released into sea and ocean waters. It's not pointless to worry because we can all make decisions about consumption.

I recently heard a story that radiation levels are elevated in both Virginia and Maryland, although it did not sound severe. Normally, I would not be concerned, but I am 12 weeks pregnant with my first child and have come to realize that things I previously didn't think twice about can now cause slight panic attacks. How much radiation is "safe" for unborn babies? Is there anything I can do to limit exposure? Thanks.

Exposure to ionizing radiation results in two broad types of adverse health effects:

- "random" = cancer and genetic changes

- "deterministic" = everything else, like skin burns

In utero exposures run the risk of childhood leukemia and other cancers, for which we thing (but don't know for certain) there's no safe dose, and growth and mental retardation, which have a 10 rem (i.e., pretty darn high) threshold for triggering such an effect. The published levels in air and rainwater are so incredibly low right now in VA and MD that I don't think there's any real risk.

I'm not worried about Americans or even the people in Tokyo, but the workers in the plant right now trying to fix the reactor. Are they all destined to die of cancer in the next month, year, or decade?

I hesitate to put this out there, but I have the same thought: I think it's very likely that the 50 who stayed behind when the 800 were evacuated have picked up a very significant radiation dose ... one that may lead to acute radiation syndrome and risk of death in the short-term. I think they are the real heroes, because such workers were desparately needed to keep the seawater pumps going!

What is the difference between radiation and radioactivity? I hear both words being thrown around a lot, and my understanding is that radiation is made up of light waves that can be harmful to humans in certain frequencies and quantities (x-rays, microwaves) and that radioactive material is from nuclear energy etc. Can you clarify?

Radioactivity = radioactive atoms that undergo radioactive decay, giving off radiation (specifically, ionizing radiation) upon decay.

Radiation = a broad term, misunderstood by the public. It can refer to either electromagnetic or particulate radiation. Electromagnetic includes x-rays and gamma-rays, but also visible light (which is not risky!), microwaves, etc. Particulate radiation includes alphas and betas.

Should I be thinking about potassium iodine supplementation for my four and six year old, we live in Florida where tests have indicated radioactive iodine in the atmosphere.

Not at this time! And, since I've been answering so many questions with claims of "insignificant levels" and "no public health risks," let me put it out there that I'm a public health guy, not a nuclear power guy -- the levels really are super-duper low right now, and taking KI would be unnecessary at best and risky (in cases of iodine hypersensitivity) at worst.

I was trained as a physical chemist and am consistently distressed by the consistent failure of publications like the Post to cite the importance of the half life of radioactive substances. Many times they don't even provide the name of the element or list of elements. The level of concern folks might have could perhaps be ameliorated somewhat if they understand that at least relative to iodine, the short half life means the risk lessens quickly over time. Clearly the converse obtains for elements with long half lives. The media should make it easier for people to understand the connection between half lives and the duration of risk. Am I off base on believing this might be helpful?

I-131 has an 8-day physical half-life, which means that half the radioactive atoms decay (and, equivalently, the amount of radioactivity is halved) in 8 days. In addition, the body clears iodine, so its residence time in the body in its radioactive form is even shorter. So, I do think it would be nice for the media to explain all of this!

How safe is it to buy non-food related goods from Japan?

I think it's entirely safe.

Based on current data, what is the absolute, worst-case scenario, how likely is it, and when might that occur?

Goodness - virtually impossible to answer. Not Chernobyl, but potentially still something significant.

How does the current exposure to radioactive iodine from Japan compare to the exposures that we experienced in the 50's during aboveground testing of weapons in Nevada?

No comparison - the 50s was a ton more!

At what radiation level should people start to take iodine pills to prevent thyroid cancer, and where can the public find these radiation levels listed. The news media uses terms such as low level, trace level etc. to describe the radiation coming to this country from Japan. Not useful at all.

There's no magic answer to the 'what level?' question, but it would have to be at a level that would produce a significant increase in thyroid cancer risk. For comparison, the EPA action level for beta emitters in drinking water produces an annual dose of 4 millirem ... compared with the 300-350 millirem we all pick up anyway. In other words, even at the action level, the incremental risk is incredibly small.

A big surprise for me was the ban on small children drinking tap water in Tokyo. Do you agree with different acceptable levels of radiations based on age? Can you speculate on how the water source for Tokyo's tap water supply was contaminated? Do you agree with the no minimum threshold concept?

I think that ban was "prudent avoidance" - not based on actual risk but an abundance of caution. I do think it makes total sense to have age-range-specific recommendations given the biology of the thyroid and thyroid carcinogenesis.

Whether or not any carcinogen, including chemical carcinogens and ionizing radiation as a physical carcinogen, has a threshold (i.e., a minimum required dose for any risk to accrue) is an ongoing topic of hot debate. Operationally, in public health we assume no threshold ... but that's to be conservative (i.e., we'd rather risk overprotection than underprotection).

Are/can radiation levels be large enough to affect the health of individuals in the United States?

Right now, absolutely not. Could something catastrophic happen that would threaten our health? Yes, but the threat would be cancer down the road, not an acute radiation syndrome.

Student studying abroad in Paris right now. Is the radiation cloud over us something to worry about? I was just out in the rain and my host mother is trying to tell me that I should shower ASAP. I feel as if this might be a bit much?

For me, "a bit too much."

Considering the long half lives of some elements and all the man made releases that continue to happen, are the so called "normal" background radiation levels slowly creeping up such that, eventually, the "new" normal will be well above the "old" normal?

We have years and years and years of environmental monitoring - what constitutes normal background is pretty darn well understood. While that background can, in certain circumstances and locations, creep up a bit over time, significant accidental releases never "recalibrate" background in the sense of 'background is acceptable.'

We've heard a lot about cesium and iodide, but now we are hearing about plutonium. What added concern does plutonium bring?

It goes to bone and liver, whereas iodine targets the thyroid and cesium has a broad distribution in the body.

As a scientist, do you ever foresee a time when we can overcome our fear of radiation and our inability to leverage its potential? Afterall, we live in a radioactive world, in fact a radioactive universe. Surely, our science and technology should be able to progress to the point where we can leverage its benefits for our own needs?

Paul Slovic, a psychologist, is the guru of risk perception. He has lists of factors and characteristics that drive perception of risk, and radiation is his favorite example, because it has all of the characteristics: can't be sensed, involuntary exposure, risks not fully understood, risks delayed, risks include potentially fatal, etc.

I thought it interesting that the EPA gave us the radiation detected the first days it arrived here in Ca. but nothing since. Do you expect that the radiation levels have gone up over the weeks and considering also that we had multiple days of rain? Also, what would you expect the radiation levels to be in the water supply and on produce? I have been looking and there is no information being provided to the public. I would like more data and not just the stock answer of don't worry it's harmless. Give us the numbers and let us think for ourselves.

I can't comment on EPA. At the risk of being labeled a radiation lover, I really think the current levels across the U.S., including on the West Coast, are very low and of no concern ... although vigilant monitoring is a must, and I agree most communication with the public is needed.

The US is worried about Fukushima fallout reaching the US. Was that not a concern for the Fat Man and Little Boy detonations? Does atomic bomb radiation degrade more quickly? Is it much more dispersed because of the free air explosion? Is there something unique about the core radiation that causes it to be more harmful in the food and water supply? See question on Quora

Atomic bomb detonations also create releases of radioactivity that can be carried by winds for many, many miles. I imagine a social/political decision was made in WW2 regarding what to tell the public (or not).

Hi, I have been seeing reports that radiation has been detected in states such as Alabama and Massachusetts. Supposedly the radiation was brought in by the rain showers we recently experienced. If radiation is present, how will it affect our health? What is the government going to do to keep its citizens safe? How can we keep ourselves safe?

Bottom line: Wind is carrying radioactivity from Japan, in very, very small - but detectable - amounts across the U.S. Some of that radioactivity ends up in rain, where it reaches the ground. So far, the amounts are negligible, and have only been detected because of the extreme sensitivity of most radiation monitors in environmental use.

Lobsters feed on plankton, or so I am told, which according to Webster's New World College Dictionary is "usually microscopic animal and plant life found floating or drifting in the ocean or in bodies of fresh water, used as food by nearly all aquatic animals." I therefore would care to know if this Japanese nuclear leaking would affect our American caught lobsters? Thank you for your time.

We won't really know the ultimate types, quantities, and environmental distribution (world-wide) of releases for some time. So, the answer could swing in either direction.

I enjoyed our chat. Stay vigilant, but please don't be anxious ... at least for now! Best wishes, Jon Links

In This Chat
Jonathan Links
Jonathan M. Links, Ph.D. is a medical physicist, with a B.A. in Medical Physics from the University of California, Berkeley (1977), and a Ph.D. in Environmental Health Sciences (with a concentration in Radiation Health Sciences) from Johns Hopkins University (1983). Dr. Links is currently Professor and Deputy Chair of Environmental Health Sciences in the Johns Hopkins Bloomberg School of Public Health, with joint appointments in Radiology and Emergency Medicine in the Johns Hopkins School of Medicine.
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