Ah...checking the article I see:
“Mother mice that got radiation doses between 0.7 and 3 centigrays had more pups with browner coats than did sham-irradiated mice. Browner coat colors among mice exposed to low-dose radiation were associated with higher levels of DNA methylation on the agouti gene, indicating that radiation does something to alter the chemical tagging.”
So irradiating the young altered their DNA. Not something we want to try unless you are a “viable yellow agouti mice”.
Correction - the latest version of the National Academy of Science Biological Effects of Ionizing Radiation is the BEIR VII.
“BEIR VII focuses on
the health effects of low levels of low linear energy transfer (low-LET) ionizing radiation such as x-rays
and gamma rays. The most recent BEIR report to address low level low-LET radiation was the BEIR V
report published in 1990. Humans are exposed to ionizing radiation from both natural and man-made
sources (see Figure 1). Very high doses can produce damaging effects in tissues that can be evident within
days after exposure. Late effects such as cancer, which can occur after more modest doses including the
lowdose exposures that are the subject of this report, may take many years to develop.”