Cigarette filters are basically ineffective at reducing the incidence of cancer [1][2]. They're more or less just a placebo for cancer prevention.
When people started realising how bad smoking was in the 50's, the tobacco companies started manufacturing filtered cigarettes, which had the appearance of being less harmful. They even added extra chemicals to make used filters appear darker than they otherwise would, so that they appeared to be filtering more effectively [3].
You know how the filter gets yellow after smoking? It’s not tar, it’s a coloring applied to the filter to make smokers think the filter is doing something.
