Settling The LNT Debunking Study

I don't know how many times this study has been proffered as debunking LNT.

(This might be a good time to review my webpage "LNT Model & Radiation Studies", right hand side of this page)


We're talking about cultured cells here, which is at the bottom of the evidence pyramid.

The study uses Radiation Induced Foci (RIF's) as proxies for Double Strand DNA Breaks (DSB's) and the DSB's are used as proxies for cancer risk.  It should be noted that not all RIF's are created equal, some may have x number of protein 1 and y number of protein 2, etc. and another RIF (especially with different cell types) may have other numbers of proteins making up the RIF.  The protein stained in this study is called p53.

Recall that LNT theory involves TWO "lines", not one!  There is a high dose/dose rate line we can observe epidemiologically.  And there is a low dose/dose rate line which is inferred from higher dose human evidence, animal studies and cell studies.  The ratio of the two lines is called the DDREF.

We expect a different linear slope for doses above about 2 Gy, and those below about 2 Gy.  The current estimated DDREF is 1.5, with a range of 1.1-2.3.  Cellular DDREF studies have shown a range of 2-4.

So let's return to the study which "debunks LNT".

They got 15 RIF/Gy at 2 Gy and 64 RIF/Gy at 0.1 Gy, a factor of 4.3 (64/15 = 4.3), which is consistent with other cellular studies.

But RIF's are just proxies of DSB's, we really care about number of DSB's.  The study says:

"Assuming 35 DSB/Gy, β = 35/α and based on our data, it increases with dose: β ∼ 1 DSB/RIF at 0.4 Gy, suggesting a one-to-one correspondence, whereas there would be β ∼ 2.3 DSB/RIF after 2 Gy."

Translating then, we have (2.3 x 15) DSB/Gy at 2 Gy, and (1 x 64) DSB/Gy at 0.1 Gy.

Now our cellular DDREF becomes 1.9 (64/34.5 = 1.9), again consistent with other cellular DDREF's AND the DDREF we use at the human level.

This study does not debunk LNT, it is consistent with it.