This article Denuclearize-or-lose-our-species-multigenerational-effects-of-exposure-to-radiation/ illustrates why radiation exposure is never safe. See below for my thoughts on the "holey" genome being produced as result of environmental exposures to genotoxins and epigenetic triggers or silencers:
The Holey Human Genome
My hypothesis is that de novo mutations and subtle, but adverse, alterations in genetic expression are being caused by exposures – both internal and external – in excess of the expected rate of mutation in humans. Exposures include chemicals, toxic elements (e.g., lead, mercury, radiocesium, etc.) and electromagnetic radiation.
We evolved under electromagnetic radiation and many toxic elements are indigenous to earth, although humans freed them from their mineral matrices and created in abundance radionuclides rarely if ever found at all on earth, including Plutonium-239 and Cesium-137.
Unfortunately, there is no definitive baseline for human rates of mutation prior to the industrial era. All we have are recently developed baseline figures, which are really simply estimations. For example, Durbin et al (2010) estimated the rate of de novo germline base substitution mutations to be approximately 10−8 per base pair per generation (Durbin, Richard M. Nature. 10/28/2010, Vol. 467 Issue 7319, p1061-1073).
Getting a handle on epigenetics is even more complicated yet we know that chemicals and viruses can alter gene expression, among many other potential triggers.
The effect of increased rates of genetic mutation and epigenetic instabilities would be most likely to be expressed in chronic diseases and/or syndromes rather than discrete bodily deformations: neurological syndromes, immunological syndromes (especially inflammatory responses), endocrine syndromes, etc. Often people with syndromes have comorbid conditions.
Acquired mutations and genetic alterations in eggs, sperm, and mitochondrial DNA will be transmitted across generations. Think cascading failures as a result of too many subtle alterations of genetic expression across time.
Fukushima Daiichi Steaming this Morning