Exposure science differs from past approaches in the environmental sciences, because, instead of beginning with an assumed source of pollution and then trying to find out who or what may be affected, exposure science works from both directions — not just from the source but also backward from the receptor. In the past, environmental policy analysts have assumed some obvious source, such as a smokestack or a leaky drum, may be important and then tried to trace where the pollutant goes, often losing its complicated trail long before the much-diluted pollutant ever reaches any real people, plants, or animals
