In the past, waxed paper cup is used the most often. It´s soaked in the wax and can only hold cold drink. It can not hold anything that contains oil since wax is dissolved in oil. At around 40℃, wax will melt and wax contains carcinogen---polycyclic aromatic hydrocarbon.
Nowadays, the most commonly used is the paper-plastic cup. Its outside is a layer of paper and the inside a layer of coated paper,which is a kind of plastic film lined with polyethylene. Though the outside is paper, the inner plastic film is the one that contact food,so it´s controversial whether this cup is defined as paper cup or plastic cup. When detected,both the quality of the paper and plastic are detected.
Without wax, people may think the paper-plastic cup is safe. In fact, there are a lot of dangers. The hidden danger of the sanitation of the outside paper is outstanding. If the outside contains water, moulds will emerge and paper cups are stacked together,which means that once there are moulds outside ,the inside will surely be polluted. When using a paper cup, be sure that it´s not wet and moldy. Next, it´s the printing ink on the outside, there is the pungent taste,which is the smell of the ink.If the smell is heavy, it means that the cup is substandard. A lot of printing ink contains benzene and toluene and benzene is the recognized carcinogen. At present, printing ink containing no benzene are used in US and Japan but in China we still use printing ink that contains benzene.
Some paper cups may be made of waste paper and to make the cup look whiter, bleachers are used during production. Some manufacturers even use fluorescent powder for whitenning. According to national regulations, fluorescent powder should not be used for paper related to food. Thus, the whiter the cup,the more dangerous .
As for the plastic film inside the cup, if it´s plastic of food grade and meets national requirements, that´s ok. If industrial plastic is used, plasticizer is added to increase the tenacity and stiffness of the cup. If too much plasticizer is added or illegal plasticizer is used, the satiation can not be guaranteed.
Dong jinshi suggests that we should use less disposable paper cups or scientifically use them. Paper cup of the same color is suitable for hot drinks and become stiff when heated. Plastic cups become stiff when cooled and it´s better used for holding cold drinks. Paper-plastic cups must not hold oily things since oil could penetrate plastic; The penetrability of fluorescent powder and the printing ink is strong, it will contaminate food, so the paper box of instant noodles should not be placed in the microwave oven for heating.