I'd have to go way back, and actually feel inspired to do it, but I don't think it was just as issue of plastic not breaking down in landfills either, if I remember correctly there were other concerns, like toxic burn off if waste was incinerated instead of taken to landfills, small particle matter from burn off causing them to change out their filter systems, if I remember correctly, was also a concern. Maybe I am more aware of it because our city decades ago went to incinerating waste materials. Not all our city's waste gets incinerated, just another option they added to handle waste.