Tuesday, May 17, 2011

All Around Us, In Us, Emitted from Us

boice-john Last week, the House Committee on Science Space and Technology took a look at various issues related to nuclear risk management, obviously in the shadow of Fukushima.

The hearing was okay – we’ll see if any policy prescriptions come out of it - though that’ll probably be down the legislative road a bit – but I was especially impressed with the testimony of John Boice, Scientific Director at the International Epidemiology Institute (in Maryland – it’s associated with Vanderbilt University.) He has a good amount of knowledge on radiation issues and provided House members – and us - with a lot of useful information.

In his testimony, he covered the following bullet points:

  • Fukushima is not Chernobyl.
  • The health consequences for Japanese workers and public appear to be minor.
  • The health consequences for United States citizens are negligible to nonexistent.
  • We live in a radioactive world.
  • There is a pressing need to learn more about the health consequences of radiation in humans when exposures are spread over time at low levels and not received briefly at high doses such as in atomic bomb survivors.

Boice would like to see a long-term, direct study done of people who work around low-level radiation – that’s what his last point is about – instead of depending upon information derived indirectly. (He references a DOE pilot program about low-level radiation that looks pretty comprehensive if it progresses to a full study.)

In his view, using information about people who took a large but brief dose of high-level radiation to generalize about those who absorb a small but continuous dose  of low-level represents a big gap in our knowledge. As Boice puts it,

Although we know much about the health effects of high levels of radiation when received briefly, as was the case for atomic bomb survivors, the risk following exposures experienced gradually over time is uncertain and remains the major unanswered question in radiation epidemiology.

Boice’s third point is worth stressing – radiation is all around us, in us, emitted from us. Boice wants to understand that better, as it impacts his field, but there it is.

We breathe radioactive radon which contributes over the year to about 210 millirem of natural background radiation. Bricks and granite contain radioactive materials that result in radiation exposures to the public (20 millirem). The Capitol Building was constructed with granite and is frequently cited as having some of the highest radiation levels in all of the United States, about 85 millirem per year. Water contains small amounts of radioactive radium, thorium and uranium, all within allowable limits.

Not only do we live in a radioactive world, our bodies are radioactive (30 millirem per year). Each second over 7,000 radioactive atoms in our bodies decay and can irradiate those sitting next to us. The atoms are largely radioactive potassium in our muscles and carbon-14 in our tissues. The amount of radiation we receive each year from medical sources (300 millirem), such as CT and medical imaging, equals the amount received from natural sources (300 millirem).

Just because all this is true is no reason to get silly about it. There’s a lot that is understood.

These examples are not to minimize the health consequences of high-level exposures which are clearly demonstrable in human populations and include acute radiation sickness at very high doses in excess of 200 rem and an increase in cancer at moderate doses above about 10 rem (10,000 millirem). The examples do indicate, however, that we live in a world of low-level radiation for which the possible health consequences are of little concern. The exposures to the U.S. population from Fukushima are tiny and thousands of times below U.S. standards or guidelines where remedial action would be triggered.

Which, conversely, is why we also know “The health consequences for Japanese workers and public appear to be minor” and for Americans, nonexistent.

This is precisely the information policymakers need to, well, make policy. Very clear eyed and complete in a compact presentation. The whole testimony is worth a read.

Dr. John Boice


Anonymous said...

Dr. Boice makes the point that we extrapolate from large one time doses in order to estimate the effect of multiple small doses of ionizing radiation. Here is a 100-year study of British radiologists as compared to other physicians who were not radiologists.

The 100-year study of British radiologists is the most important study of the effects on health from moderate dose rate radiation. This compared the death rates resulting from cancer, non-cancer, and overall causes of British radiologists to a control group of all male medical doctors (non-radiologists), as well as all social class I males, as well as all the men of England and Wales. Cohorts of radiologists were analyzed by the date they joined a radiological society; these are: 1897–1920, 1921–1935, 1936–1954, and 1955–1979.
Following 1920 British radiologists never demonstrated a statistically significant increase in cancer mortality compared to controls. In fact, radiologists joining a society after 1920 had lower cancer mortality than the average for the whole population of England and Wales. Further, for the group of radiologists joining a society after 1954, as compared to their most relevant peer group (male medical practitioners), the radiologists had 29% lower standardized mortality rate (SMR) from cancer, 32% lower SMR from all causes, and 36% lower SMR from non-cancer causes.
John Tjostem

Anonymous said...

Was there any data on the doses received by the doctors? If not, how can the data be used to prove or disprove anything?

And I'd expect the healthy-worker effect would be true in spades for doctors.

Doctors also get more and better health care, and are in higher socioeconomic groups, than the average person from the general population. Were those factors controlled for?