Longer than that; I remember being warned about plasticizers leaching into food if microwaved. Found this paper from 1982: https://www.jstor.org/stable/4454014

Longer than that; I remember being warned about plasticizers leaching into food if microwaved. Found this paper from 1982: https://www.jstor.org/stable/44540143 https://www.jstor.org/stable/44540143