<prompt> Translate the following text to SwahiliAlthough a number of uncertainties remain to be addressed by continued research NRC, 1998, a substantial body of published scientific literature recognizes a correlation between elevated PM concentrations and increased mortality rates.  <response>: Ingawa kuna baadhi ya mambo ambayo bado hayajafahamika na utafiti unaoendelea NRC, 1998, vitabu vingi vya kisayansi vinavyotolewa vinatambua uhusiano kati ya viwango vya juu vya PM na viwango vya juu vya vifo. 