Here you go, here's one plain vanilla dictionary definition, absent context.
Now would you like to discuss which "substances produced by chemical processes" are likely to be the most impactful upon the environment, or would you like to continue quibbling over semantics?
chemical [ kem-i-kuhl ]SHOW IPA
noun
a substance produced by or used in a chemical process.
chemicals, Slang. narcotic or mind-altering drugs or substances.
adjective
of, used in, produced by, or concerned with chemistry or chemicals: a chemical formula; chemical agents.
used in chemical warfare: chemical weapons.
https://www.dictionary.com/browse/chemical