Fukushima meltdown and glow-in-the-dark Californians?

I’m a big fan of recycling and this is a re post of something I wrote in 2012 but which is still worth reading as a reminder that chicken little syndrome can be combated by a little background reading.

It seems people are getting all bent out of shape about this report.

http://iopscience.iop.org/1748-9326/7/3/034004/article?v_showaffiliations=yes

Temporal evolution of absolute peak concentrations (in Bq m−3, logarithmic scale; grey shaded) and within individual regions (see figure 4(d)) from the 0.1°-model simulation, assuming a total input of 10 PBq of 137Cs. Regions: western Pacific (I, black), off North America (II, green), Hawaii Islands (III, light blue), off Baja California (IV, blue), Aleutian Islands (V, red). The inset is a zoom into the part of the figure with levels below 2 Bq m−3 (pre-Fukushima values) on a linear scale.

Caesium isotopes coming our way are not a good thing and there may be a problem but not based on this report.

The peak level of isotope on the US pacific coast is projected to rise to double the current background radiation, which sounds bad but even at the peak, it will be less than 4Bq/m^3. To put that in perspective, you would need to drink over 250m^3 of the contaminated seawater (that’s well over 250 metric tonnes) to exceed the maximum safe contamination level of a single kilo of food (WHO recommendation, which assumes consumption of 750kg of food contaminated to that level per year) so unless you plan to drink 250 tonnes of seawater twice a day for a year you shouldn’t experience any problems.

The other statistic (gleefully misreported by the press) is that excess contamination levels on the US pacific coast six years from now will be ten times the level experienced in Japan; a truthy little factoid which has been seized on by a number of eco-bloggers who are in major panic mode that we are all going to start glowing in the dark.

Now, ten times sounds bad, but only if you think that, by some miracle of concentration, they mean ten times the peak level immediately after the fukushima meltdown but what they actually mean is that, by the time the excess radiation level here reaches the same level as existing background radiation (doubling the total), the excess radiation in Japan will have fallen to only 10% higher than background. So our excess radiation will be 2Bq/m^3 when theirs is down to 0.2Bq/m^3; that’s 10x sure enough but the TOTAL radiation levels will be 4Bq/m^3 vs 2.2Bq/m^3 which is less than twice and our level will never come within four orders of magnitude (1/10,000) of the levels seen in Japan.

By the way, the biological half life of C-137 (ie: after it has been ingested by an animal) reduces from >30 years to about 30 days so this is not something which is going to persist in the food chain.
So I think I can say that I feel pretty reassured that there will be no water borne problems in California as a result of the Fukushima meltdown.