<prompt> Translate the following text to EnglishHii ni dhana muhimu, kwa sababu chembe ndogo kutoka kwa uzalishaji wa mitambo ya umeme ni tofauti na kemikali kutoka kwa chembe ndogo zinazotolewa moja kwa moja kutoka kwa vyanzo vya simu na vifaa vingine vya viwanda, lakini hakuna msingi wa kisayansi wa kuunga mkono makadirio ya athari tofauti kwa aina ya chembe.  <response>: This is an important assumption, because fine particles from power plant emissions are chemically different from directly emitted fine particles from both mobile sources and other industrial facilities, but no clear scientific grounds exist for supporting differential effects estimates by particle type. 