Cortinarius caperatus found to be infested with maggots when picked. Mycologist David Arora recommends discarding the tough stipes. The popularity of "C. caperatus" across Europe has led to safety concerns related to its propensity to accumulate contaminants. Fungi are very efficient at absorbing radioactive isotopes of caesium from the soil and naturally have trace amounts of the element. Caesium may take the place of potassium, which exists in high concentrations in mushrooms. "C. caperatus" bioaccumulates radioactive caesium Cs—a product of nuclear testing—much more than many other mushroom species. Levels dramatically rose after the 1986 Chernobyl disaster. This is a potential health issue
Caesium inside old stars and by the R-process in supernova explosions. The only stable caesium isotope is Cs, with 78 neutrons. Although it has a large nuclear spin (+), nuclear magnetic resonance studies can use this isotope at a resonating frequency of 11.7 MHz. The radioactive Cs has a very long half-life of about 2.3 million years, longest of all radioactive isotopes of caesium. Cs and Cs have half-lives of 30 and two years, respectively. Cs decomposes to a short-lived Ba by beta decay, and then to nonradioactive barium, while Cs transforms into Ba directly. The isotopes with mass numbers of