Tuesday, May 3, 2011

Why the EPA Limits for Drinking Water Are Irrelevant to Radiation From Japan

Originally published as a note on my Facebook page Apr 25, 2011

The most recent results for iodine-131 levels in milk in Arizona have been widely misrepresented in media coverage as 1600x the EPA limit for drinking water. In fact, it's 16x (1600%), however, even that is meaningless. In fact, the EPA doesn't have a level for milk, and comparing it to the drinking water level is flawed as a level for milk and drinking water would not the same due to the differences in daily consumption. So any comparison to EPA levels is complete nonsense. The EPA levels serve a different purpose than the FDA levels, see info on EPA levels below. BTW, AZ publishes the readings from testing water and milk at http://www.azein.gov/azein/2011/Data%20landing%20page.pdf

The FDA sets limits for food and drink (including milk and drinking water), and the highest level reported is ~ 1/1000 of the FDA DIL (Derived Intervention Level). Now the FDA DIL is probably too lax for drinking water because of the amount of water consumed daily. For food and milk, the FDA limits are better, but are arguably still too lax (at least for extended exposure). However, they're far more appropriate to a transient exposure, and they're specific to ingested food and drink, so they're far more applicable than the EPA levels in this situation.


More info on EPA limits:
EPA limits are based on consuming the MCL every day for 70 years, which is to say they are for a maximum "every day" level, not a maximum "safe" level. The EPA levels don't differentiate between getting the MCL every day for a lifetime and getting a somewhat larger dose for a few days. As a maintenance level, it make some sense, but they don't address transient levels. They are flawed in other ways as well, for instance, they allow 5x higher dose from alpha emitters which are far more damaging when inhaled/ingested than they do for beta and gamma emitters. They allow 5x as much exposure to a type of radiation that is ~ 20x more damaging, how does that make sense?

The EPA limits are occupational exposure limits (Quoted from 40 CFR 141.66(d)(2)):
"Maximum Permissible Body Burdens and Maximum Permissible Concentrations of Radionuclides in Air and in Water for Occupational Exposure," NBS (National Bureau of Standards) Handbook 69 as amended August 1963, U.S. Department of Commerce.


Another article on why the FDA and EPA limits are so different.

A group of scientists working to update what is classified safe exposure levels, based upon the scientific evidence.
Time for the scientific, environmental and economic truth about nuclear power

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