"An Ecosystem's Disturbance by a Pollutant Freedman defines a pollutant as "the occurrence of toxic substances or energy in a larger quality then the ecological communities or particular species can tolerate without suffering measurable detriment" (Freeman, 562). Although the effects of a pollutant on an organism vary depending on the dose and duration (how long administered). The impact can be one of sublethality to lethality, all dependent upon the factors involved. These factors need to be looked at when determining an ecosystem's disturbance by a pollutant. Some of the most frequent pollutants in our ecosyste