My husband doesn't believe this and does it all the time. The practice can be harmful. Plastic is made from oil, and burning it liberates fumes and vapors that can be dangerous if inhaled. Many of these hydrocarbons are carcinogenic. Moreover, they cause air pollution and may be associated with chronic pulmonary disease.
Some plastics are highly flammable.
My husband splintered a rib in an accident several years ago. Once a rib is fractured, it will heal in about two months, as will any other normal broken bone.