Protecting Against Nothing: The Failings of ALARA

Partial list of EPA drinking water regulations

ALARA and Reason

In Howard Shaffer's recent guest post: "No Safe Dose" Is Bad Science,  Shaffer described the questionable science behind the Linear Non Threshold (LNT) standard for radiation protection.  In my introductory remarks for his post, I wrote this sentence:

"Protecting" against very low levels of radiation increases the cost of nuclear plants, but the LNT (Linear Non Threshold) model says we must protect against any level of radiation, no matter how small.

An anonymous commenter asked a question about this statement.  He didn't ask directly about LNT.  He asked about LNT's daughter:  ALARA (As Low As Reasonably Achievable). LNT claims that no radiation dose is safe,  and ALARA claims that we must continually attempt to decrease the amount of any radiation dose.

So, back to the commenter's question.   I had claimed that LNT forces us to protect against "any level of radiation," and he asked:

How would you reconcile that statement with the actual U.S. regulatory regime, which relies on the As Low As Reasonably Achievable approach? (Emphasis in the original statement.)

Mineral Water

"Reasonable" is Unreasonable

My answer (edited a bit from the original that I posted).

The term "reasonable" is intrinsically unreasonable. How is reasonable defined? By whom is it defined?

Here's a simplified example of the difference between "reasonable" levels and a threshold level. My town water meets threshold limits for safety. My town provides town water and it sends residents the analysis results for their water. I am proud to say that our town has an excellent municipal water department. The water is safe to drink: all ions and all contaminants are below the EPA levels that define safety for those materials. 

Let's say the EPA safety limit for "A" is 10 parts per million (ppm).  Let's say, in the town water, "A" is at the level of 5 ppm. 

The water is safe. 

Town water and threshold limits

The water is safe, and people can't go to the town select board and insist that new water treatment methods are available and therefore must be acquired by the town.  They can't insist that the town needs to lower the level of "A" from half the EPA safety limit to a quarter of the limit. People can't force the town to upgrade its water system just because those people believe that the new lower limit is "reasonably" achievable. Once the  town water has met  its threshold for safety, further water treatment is not required.

That's the difference between a threshold level--and the unreasonable term "reasonable." 

• A threshold is a number. A system (water supply, power plant) can do a measurement and prove that it meets the criteria. 
• In contrast, the term "reasonable" is open to endless expensive interpretations.

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Note: The commenter then asked a second question.  I will answer it in a separate post.