Why does cigarette filter turn black?

[bansheepimp4life]

Lately I've noticed that when I smoke I'll get halfway through the cigarette and I'll notice a nasty bitter taste and when I look one side of the filter is black it hasn't always done this , I smoke Marlboro black menthols by the way

[Mintee]

I absolutely cannot believe you are asking this question..
think about it.. what is the purpose of the filter? to filter out the smoke,tar, nicotine.. so hense
it will turn dark... thats obvious

[Duddd]

no wonder you smoke...

[Duddd]

no wonder you smoke...

[timlewis]

that's crazy. knowing Marlboro they've probably started filling the cigs w black tar heroin. try newports , they're yummy. and don't do that. ever.

[JacksonMcFail]

It's the opposite of Michael Jackson.