Confused about plastic

Not yet begun UltraMetabolism Not yet begun UltraMetabolism

Doing the UltraSimple Diet Doing the UltraSimple Diet

I know Dr. Hyman (among others) recommendeds using glass over plastic, but sometimes that's impractical. (Are the meals you can buy delivered in plastic trays?) What plastics are okay to use?  I have recently heard that plastic #7 is one of the worst to use.  However, most of the "harder" plastics are made of this.  I thought Dr. Hyman recommended using harder plastic.

 Does anyone have any clarification on this matter?