PlasticList – Plastic Levels in Foods

It's interesting that several products from the 1920s contain measurable quantities of DEHP, which was apparently first synthesized in the 1930s. How did that happen?

For example, the cocoa powder from the 1920s https://www.plasticlist.org/product/990

That is interesting. I wonder if it's a byproduct of another process and the 1930s date was only when it was commercially produced in isolation.