Every generation has some product/ingredient that they didn’t know was dangerous at the time: tobacco, lead, asbestos, etc. What is that item for this generation?
Yes, all plastics. Even bpa free plastics leak estrogenic chemicals into food, and fpod is often stored in plastic containers. Even milk cartons are lined with plastic.
Teflon(nonstick coated pans and pots) arr similarly terrible
Shoes with a raised heel is bad for your knees. (Easily measurably bad. Especially for running)
It wont be hard, its the rarest material in the universe. Entire planets can be made of diamond. But of planets with life for millions of years, then with intellegent life capable of finding, processing and spreading it. Well it may only have happened once.