<prompt> Translate the following text to EnglishHata hivyo, majukumu ya jamaa ya muda wa mfiduo wa PM na kiwango cha mfiduo wa PM katika kusababisha vifo vya mapema bado haijulikani kwa wakati huu.  <response>: However, the relative roles of PM exposure duration and PM exposure level in inducing premature mortality remain unknown at this time. 