Smoking is bad for your health but it’s also not great for the environment either. This has nothing to do with actual toxins from the smoke and everything to do with the product itself. Not the whole thing, mostly just the plastic filters. These little bits of waste go on to cause a good deal of pollution.
A lot of the pollution is caused by the fact that people tend to toss the filters from their finished cigarettes just anywhere they happen to finish smoking, whether there is a trash can there or not. This just adds to the amount of litter and they makes it way into the ecosystem from there. Which is not great.
Ironically, the filters don’t make smoking any less dangerous so some people have suggested that they be removed from the product altogether. The best course of action is end smoking completely but until then, if you’re a smoker, please be mindful of where you toss your butts.