Japanese Radiation Readings
With all the uncertainty and doomsday-scenario talk we've been getting on the news, it's sometimes informative to step back and put things in perspective.
First, let's talk about bananas. The average radiologic profile of bananas is 3520 picocuries per kg, or roughly 520 picocuries per 150g banana. The equivalent dose for 365 bananas (one per day for a year) is 3.6 millirems (36 μSv).
Another way to think about radiation is by comparing the risk from radiation-induced cancer to that from cancer from other sources. For instance, a radiation exposure of 10 mrems (10,000,000,000 picorems) increases your risk of death by about one in one million—the same risk as eating 40 tablespoons of peanut butter, or of smoking 1.4 cigarettes.
Okay, now let's look at official Japanese radiation readings:
Monitoring of radiation levels on the spot is ongoing. At point MP4, where a reading of 1,015μSv was detected yesterday, a radiation level of 44.6μSv was recorded at 00:30 this morning, and a level of 36.7μSv at 6:00am. After the start of venting around 9:20, a reading of 76.9μSv was recorded at 9:20 and of 70.3μSv at 9:30.
What does this mean? The radiation spiked up to 30 bananas a day (2 days ago) and then fell back down to 1 to 2 bananas per day.
Hmm, that doesn't sound so bad any more.
Let's look at other source of radiation hazard:
- 1400 millirem for a gastrointestinal examination series (14,000 μSv)
- 200 millirem for one year in an average house from Radon (2,000 μSv)
- 360 millirem average annual dose for someone in the USA (3600 μSv)
- 660 millirem per year for your whole career might have a life expectancy loss of 15 days
- 1360 millirem per year for your entire working career might have an expected loss of 51 days
- A manufacturing career reduces life expectancy by 40 days
- 100 rem definitely causes damage (10000000 μSv, 1 Sv)
Remember: perspective is important.
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John Rundle is a Distinguished Professor of Physics and Geology at UC Davis and the Executive Director of the APEC Collaboration for Earthquake Simulations. He chaired the Board of Advisors for the Southern California Earthquake Center from 1994 to 1996. Read John's blog.