"Harmful byproducts" refers to substances or materials that are produced as a result of a process or activity and can cause damage, illness, or negative effects on the environment or living beings. Full definition
It overactivates the immune system to produce harmful byproducts like peroxide and oxygen radicals that mutate DNA. (sciencedaily.com)
The kind of «resistant starch» that comes from plant foods like cooked beans, peas, lentils, and raw oatmeal — can block the accumulation of potentially harmful byproducts of animal - protein metabolism in the colon. (nutritionfacts.org)
Chlorine can also interact with other matter in the water to form harmful byproducts like trihalomethanes (THMs). (wellnessmama.com)