A Hard Rain
It's been a few days since my last blog. There's a lot to report from Japan, but I'm going to focus on what's happening here in the US. The main news here in the San Francisco Bay Area is the results from U.C. Berkeley's Nuclear Engineering Lab. I strongly recommend their site and its FAQ: http://www.nuc.berkeley.edu/UCBAirSampling
First, I should clear up some mis-reporting that occurred: So far there have been no detections of hazardous levels of radiation in Bay Area drinking water (as one might have interpreted when reading certain recent headlines.) ...and drinking water has been tested. So tap water is safe at present, and this lab is continuing to test tap water and I assume they will let us know ASAP if there is any increase/risk from drinking tap water.
However, it is now clear that on March 17 and afterward radioactive rain fell in the SF Bay Area. From that date forward, detectable levels of I-131 and Cesium have been discovered in rainwater samples collected from the roof of Etchevary Hall in Berkeley (trivia: I used to live on the same street, 1 block away from this building. trivia2: this building used to house a nuclear reactor!) The highest recorded reading for I-131 is 20 Bq/L recorded on 3/23. (This reading means that if you drank 1 full liter of that rainwater, then every second there would be 20 radioactive decays in your body; every hour there would be 72,000 decays) On other days, the readings were much lower, (around 5 Bq/L) but still I-131 was detectable.
What to think about this? The EPA limit for drinking water is 0.111 Bq/L, so the peak rainwater reading is 181 times over the limit. More relevantly, the average value is about 5 Bq/L, which is still about 6 times over the limit. Here are some reasons why this figure is not an automatic sign of serious danger: 1. you didn't drink that rain water, you've been drinking tap water which is fine. 2. the EPA calculated that limit assuming the person would be exposed to this level of radiation for a whole year. So you'd need to drink that rain water for a couple of months to exceed the EPA annual max. dose. 3. *IF* the release of radioactive Iodine stops, then the I-131 present in our environment now will be about 90% gone a month from now. (due to the 8 day half life) Here are some reasons to be concerned. 1. That rain fell on everything around here: roofs, gardens, farms, streams. Thus it can and will get into the food supply. (UC Berkeley is testing the food supply and has not found dangerous levels...yet) 2. If other isotopes, like Cs-137 are present, they will not decay away quickly. (30 year half life). The tables on the site above suggest that signficantly less Cs-137 is present than I-131. However I didn't see a quote for the EPA limit on Cs-137
3. We don't know how long this will go on. If the situation in Japan continues to deteriorate, then we may well be getting "fresh" rains of newly made I-131. In this case the 1 year exposure time defined by the EPA may come into play. This is why it is important to look for signs of continuing out-of-control nuclear reactions at the reactors in Japan.
Note: the Berkeley site lists (in parentheses) numbers relating to dosage of one airplane flight from SF to DC. I don't put much value in these numbers since they compare internal doses (eg. from food or water) with external doses, eg. from air flights or X-ray machines. However they do serve to remind us that we live in an environment has a small level of radioactivity. We always have & always will. This site has an animation of an atmospheric model showing how the air gets from there to here. My Thoughts: Food is extremely safe now. We don't know how long this will go on. (Today's reports of increased risks of new Hydrogen explosions at Fukushima Daiichi suggest no end in sight.) As the father of an infant, it seems prudent to me to stock up on any foods that we can make last right now while they are still safe. The radioactivity in our food may go up, but will not go down. I expect it will never exceed the "unsafe" levels. However these levels may not be created w/ infants in mind. My understanding is that there is no genuinely "safe" level of radiation. Every decay contains the possibility of causing damage to our cells and our genes in particular, however small. Since we live with background radiation every day, we need not be concerned about new radiation sources at the background level. Its when our level of exposure exceeds background that we need to start to consider taking action. Consider this question: Assuming you drive every day, what is the safe level of not wearing your seat belt? No belt once per week (1/7) is certainly safer than no belt ever. Is neglecting a seat belt once per month a safe level? After all, the odds of something happening are 1/30 times the odds of getting in a crash in the first place. A much safer approach would be to ignore your seat belt only one day per year, every year. This is 365 times safer than never wearing a belt. Is that safe enough for you or not? My answer is: if you can take some precaution w/o causing additional risk/harm, why no do it? This is why I just bought large quantities of yogurt, (high Iodine, high Calcium which is chemically similar to Strontium), strawberries (high Iodine) and seaweed (high Iodine) bananas (Potassium, similar to Cesium). I'm using these healthy foods to make items (some frozen) to feed to my son over the coming weeks and months. These foods have elements we all need anyway, so there's no downside, and the upside is the peace of mind of knowing that I've taken a step to reduce the overall risks.
Oh, where have you been, my blue-eyed son? And where have you been, my darling young one? I've stumbled on the side of twelve misty mountains, I've walked and I've crawled on six crooked highways, I've stepped in the middle of seven sad forests, I've been out in front of a dozen dead oceans, I've been ten thousand miles in the mouth of a graveyard, And it's a hard, and it's a hard, it's a hard, and it's a hard, And it's a hard rain's a-gonna fall. -Bob Dylan, A Hard Rain's a-gonna Fall