Checking Colleague Just Back From Japan For Radiation Contamination

This week, one of my veterinary colleagues returned from a 3-week visit to Japan. She was obviously worried about possible radiation exposure in the aftermath of the Japan nuclear crisis and asked for my advice about how she could check for radiation contamination.

I asked her to come to my office today so that I could monitor her for any radiation contamination.  I have the radiation instruments in both of my offices because we routinely treat hyperthyroid cats with radioactive iodine (I-131). (See my website for more information.)  My staff and I use this radiation detection equipment on a daily basis in order to check for contamination, both on our bodies and well as in our work environment (this is a safety precaution - we do NOT expect or plan on becoming contaminated!).

I first monitored my colleague by use of a general purpose survey meter (Geiger counter). With this meter, I've attached a GM (geiger-mueller) pancake detector, which is sensitive to alpha, beta and gamma radiation and is the industry standard for detecting contamination.

Fortunately, I found absolutely no detectable levels of external contamination with my measurements.

Dr. Peterson checking for external radiation contamination

We next measured my colleague's thyroid gland for internal contamination. As you may know, the principal radiation source of concern with the nuclear reactor accident in Japan is the release of radioactive iodine (I-131). This radioactive isotope that presents a special risk to health because iodine is normally concentrated in the thyroid gland. Exposure of the thyroid to high levels of radioactive iodine may lead to development of thyroid nodules and thyroid cancer years later. 

Counting thyroid gland for I-131 contamination

To measure for internal (thyroid) contamination of I-131, we used a general purpose radiation scaler/ratemeter attached to a shielded well gamma radiation counter. This is a very sensitive instrument, which allows us to detect very tiny amounts of gamma radiation, including the gamma rays (photons) emitted from I-131.

Radiation counts below background readings, indicating no contamination

Fortunately, the thyroid counts measured in my colleague (373 counts per minute or cpm) were below the background radiation counts of 385 cpm. This demonstrated that there was NO internal thyroid radiation.

Overall, we found NO external or internal contamination in my colleague. All good news!  

The fact that we measured a background radiation count is a normal, expected finding: background radiation is constantly present in the environment and is emitted from a variety of natural and artificial sources. See this article for more information on background radiation.