<prompt> Translate the following text to EnglishMakadirio ya msingi yanategemea makadirio ya athari ya uwezekano wa mkusanyiko wa muda mrefu wa kuambukizwa kwa chembechembe, wakati makadirio ya mbadala yanadhani kuwa athari za PM ni mdogo kwa wale ambao hukusanyika kwa vipindi vya muda mfupi zaidi.  <response>: The Base Estimate relies on estimates of the potential cumulative effect of long-term exposure to particles, while the Alternative Estimate presumes that PM effects are limited to those that accumulate over much shorter time periods. 