mephitic - foul
The word ‘mephitic’ does more than simply refer to air that smells horrible, it expresses something noxious that to breathe in could harm a person’s health, or at the very least assault the nostrils. It is most commonly encountered in relation to atmospheric pollution of some kind, such as poisonous fumes or a foul, gaseous cloud.
The factory was deemed to be unsafe and temporarily closed due to the mephitic fumes that were found to be leaking out of the ventilation system.
After the volcano erupted, a thick cloud of mephitic, poisonous gas swept over the surrounding area and caused a number of deaths.
The cabin in the woods was beautifully crafted and well-appointed, but I had to cut my holiday there short because I found the mephitic stench of the nearby swamp to be too overpowering.