It's supposed to be according to RAW. I wanted to experiment to see if it was possible to use Toughness check with the Toxin/Gas/Chem Delivery weapon traits. Because they are very similar. If a fighter has T3, they pass a Tougness Check on a 1-3. If hit by Toxin, they survive on a roll of 1-2. That is a Toughness check with a -1 modifier, no?