First, polyethylene. Polyethylene is composed of hydrocarbons, which produce carbon dioxide and water when it is completely burned, and carbon particles (black smoke) and carbon monoxide when it is not completely burned. Polyethylene is flammable.
Second, polyvinyl chloride. The composition of PVC is hydrocarbon chlorine, which will produce HCL when burning, and it is commonly known as hydrochloric acid after being dissolved in water. PVC is flame retardant.
If it is burning at high temperature, the operation of polyethylene has little effect on human health, while PVC is harmful to health. It is best to wear a mask.
But generally speaking, the biggest impact on human health is not polyethylene and PVC itself, but plastic additives, such as pigments. Many additives have direct harm to human body, and the harm may be even greater after high temperature volatilization or chemical decomposition.
If it is a plastic bag made of recycled plastic, there are many impurities and additives, and the gas produced during high-temperature processing has a great impact on human health.