These seven elements are guarded by seven Amesha Spentas. Polluting is like offending against the rules of purity of these elements, which in turn implies offending the Amesha Spentas.
Fire is the most sacred element in Zoroastrianism as it pervades the entire creation.
At all costs and in all circumstances it must be kept undefiled. It is very strange that Zoroastrians of USA , UK have adopted cremation for their deads, which is totally rejected in Iran. The sanctity of water is very important in Zoroastrianism. The fundamental principle in preventing pollution is also served by not urinating while standing, this checks spreading bodily waste to a larger area and consequently it is proscribed in Vendidad 18.40. Urinating while standing is further condemned in PhlRDd 11.3.