Your implication here is that Subway is setting out deliberately to poison people, like they are dropping a chemical into a city's water supply with the distinct intention of killing people.

They aren't doing that, and for you to imply they are is fatuous in the extreme.

No one forces you or anyone else to eat at Subway, or at any other FF outlet or any other restaurant, or in any other way. It's one of the distinct advantages of living in a "free" country where you are able to make choices.

Like everything else, it's a matter of Buyer Beware. If it doesn't suit you, you have the choice to move on.