The concept that “RAINDROP”want to talk about is “circulation & feedback”
A cloud is a condensation of water vapour in the atmosphere and into the rain by Gravity.Rainwater will flows into the ocean ,lakes and rivers .After a while
Until the Water molecules r evaporated into the atmosphere, and condense into raindrops falling again, This is the”water circle” that can make life on earth survived.
However, From the day human presence, for their own interests, They forced destroyed the loop which has been maintained for billions of years
With Long-standing accumulation , Pollutants affect the entire circulatory system of nature and Can not be restored anymore.
Finally ,Those heavy metals, acid rain and sewage will be accumulated by circulatory system , back to the land , back to the human.