Toughness (being resistant) is a personality stat in EXODE. It's main use is to determine health value.

Base health is:

Toughness * 2 (on the 100 scale)

Or:

Toughness * 20 (on the 10 attribute scale)

If a character is highly resistant, you will see the keyword “Tough” appear on crewfile.

Toughness is also used is a huge number of situations such as resisting to disease or other environmental factors.