Why is water pollution a concern if water is continuously cycled through Earth's systerns?

if the water is polluted then fish and water life will die and plants near by will be affected and could also die as well. its like acid rain its not good for the environment.

Explanation:

nucleic acid molecules are incredibly complex, containing the code that guarantees the four different nucleotide units comprise dna, the nucleic acid of interest to the genealogist. and one of four nitrogen-containing molecules called nucleotides