harmful or poisonous
noxious - harmful
The formal word ‘noxious’ is used to refer to something injurious to a person’s physical or mental well-being. Its versatility means that you will often see it applied in a number of different contexts ranging from something poisonous or toxic, such as a gas, to something considered morally corrupting or highly disagreeable, if not repugnant.
After the gas leak at the factory, a number of workers fell seriously ill having been exposed to the noxious fumes.
There have been calls for that controversial book to be banned. Critics claim that it is propagating noxious ideas that could corrupt the minds of younger people.
There was no way back for the government minister after the noxiousness of that political scandal. It did irreparable damage to his reputation.