Fluctuations in the Rate of Radioactive Decay of the Natural Potassium-40 Isotope Can Potentially Affect the Periodic "Spontaneous" Activity of Animals.
Understanding the Radioactive Ingrowth and Decay of Naturally Occurring Radioactive Materials in the Environment: An Analysis of Produced Fluids from the Marcellus Shale.
Nelson AW, Eitrheim ES, Knight AW, May D, Mehrhoff MA, Shannon R, Litman R, Burnett WC, Forbes TZ, Schultz MK.
Environ Health Perspect. 2015 Jul;123(7):689-96. doi: 10.1289/ehp.1408855. Epub 2015 Apr 2.
PMID:25831257
Experiments and theory of 138La radioactive decay.