At present, most of the black plastic bags used in farmers' markets are made of recycled inferior waste polyethylene particles. Most of these recycled particles are made from waste polyethylene packaging films and waste polyethylene packaging bottles after washing, crushing and granulating, but what was previously loaded is unknown. Some experts said that if these packaging films and bottles are already filled with toxic and harmful substances such as fertilizers and pesticides, it is impossible to clean them all simply by washing.