the.com/pollutant

means A substance that, once released into air, water, or soil, causes harm to the environment or living things.

from From Latin 'polluere' — 'to soil, defile, contaminate' — built from 'pol-' (variant of 'por-', toward) plus 'luere', a form tied to washing or dirtying. The word stayed mostly about moral and physical defilement — polluted temples, polluted souls — for centuries; the specific 'chemical or waste substance fouling the environment' sense is a modern narrowing, growing heavy use only as industrial pollution itself became a named problem.