Rad (a.k.a. Nuclear Radiation)

Rad is not a very important issue in Carcass in the Afterfall. By most accounts, it's been roughly 300 years since The Fall.
However, it is not something totally unfamiliar either, most people know about it.
Radiation sticks not only to places, but to objects. Unbelievably, after a few decades, the site where a nuke exploded doesn't have much radiation. Nonetheless, you may find a shady rusted barrel that leaks a weird fluorescent liquid... Or something as innocent as a shoe... that somehow got insane levels of Rad. You may never know how the Rad got into the shoe. Heck, you may even drink Rad contaminated food or water without knowing it.
For the sake of simplicity, Rad exposure in this game is measured in a scale from 0 to 5. 0 means no Rad, and 5 means quick death for most characters.

To endure Rad, you need to Roll Vigor alone, against Standard Difficulty plus the level of exposure.
If you succeed, nothing happens, if you fail, you get 1 Fatigue level caused by Rad.

• Level 0: The average Afterfall wasteland... Like a site that received a bomb in the past. Below 0.001 mSv/hr.
• Level 1: Roll Vigor every 6 hours. - Recommended limit for radiation workers every five years, but in 1 hour. 100 mSv/hr.
• Level 2: Roll Vigor every 1 hours. - Fukushima Daiishi Nuclear Plant the day of the disaster (Max.). 400 mSv/hr.
• Level 3: Roll Vigor every 30 minutes. - Enough to cause Rad Sickness. 1000 mSv/hr.
• Level 4: Roll Vigor every 5 minutes. - Chernobyl workers, half of them died within a month. 5000 mSv/hr.
• Level 5: Roll Vigor every 1 minute. - Chernobyl's Reactor 4, the day after the disaster. 300000 mSv/hr.

http://www.chernobylgallery.com/chernobyl-disaster/radiation-levels/  

Rad and Mutations

Rad exposure is mutagenic, if you get Fatigue levels due to Rad, you may develop a new mutation, beneficial or an Aberration... To know the mechanics, take a look at Stress Induction.