A toxic environment can come in all kinds of forms. Toxic relationships can show up at your workplace, with your friends, and in your family too. It's sad, but that's the truth, and as we've said, the truth sometimes hurts.
A toxic environment isn't really something you can measure. It isn't empirical research, because it depends on a subjective feeling and it's different from one person to the next. That said, if you're in an environment where negative behaviors happen routinely, without anyone even questioning them, then that's the standard and that's the norm, meaning that's the accepted way of doing things. Chances are you're in a toxic environment, if only because there are no consequences for those negative behaviors.
If you walk into a room that has a bad smell in it and you stay there, at a certain point it stops smelling. Why? Because you end up getting used to anything. Don't agree to get used to anything at all, and certainly not to garbage! It's our responsibility to keep checking where we are and to ask whether this environment is good for me or not. Being in a toxic environment, and it doesn't matter whether that's a workplace, friends or your partner, will destroy you. And if there are any dreamers in the audience who think they'll change the environment, here's what I'll tell you: chances are much higher that a toxic environment will change you than that you'll change it. The proof: you can take a good person and put them in a bad environment, and that person will do bad things. And the reverse too. You can take someone who's nothing at all, put them in a supportive, encouraging environment, and they'll turn into a good person and even a leader! Which means the environment is critical.