Safety of commonly used plastic tableware

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People’s daily life – including clothing, food, shelter, and transportation – relies on plastic products. From aircraft that fly in the sky to shoes worn on people’s feet and clothes they wear, as well as household appliances such as televisions, computers, and mobile phones that we use every day… What people come into contact with on a regular basis are plastic bags used for packaging food, plastic containers for storing food, plastic bottles for drinking water, and tableware used for eating. The safety of these plastic products is what concerns everyone the most. Many people, while using plastic products, wonder: Are plastic products really toxic? To this end, this magazine has specially invited Dr. Jiang Jia□, Vice President of the Shanghai Nutrition Society and chief physician, to discuss the safety of commonly used plastic tableware. Related to safety are plastic additives. Plastic is a synthetic polymer compound; there are currently over 300 different types of plastics. The main component of plastics is synthetic resin, and various additive materials are often required for each plastic product, such as fillers, plasticizers, stabilizers, colorants, lubricants, etc. In some cases, flame retardants, foaming agents, antistatic agents, and others are also added. **Plastics approved for use in food packaging are generally safe, but it is the auxiliary materials that are most closely related to safety. Fillers: The function of fillers is to improve the strength and heat resistance of plastics, as well as to reduce costs. Commonly used ones include silica, talc powder, and so on. Plasticizers: The purpose of plasticizers is to increase flexibility; common ones include phthalates, glycerol stearate, and various additives containing heavy metals. Phthalates are environmental endocrine disruptors that have hormone-like effects and can impair the functions of the endocrine and reproductive systems. Abroad, their use in food packaging was restricted or banned in the mid-1990s, and in 2005 the European Union mandated a ban on their use in children’s toys and products. Stabilizers: Stabilizers are used to prevent synthetic resins from decomposing or being damaged due to light and heat; common ones include stearates and thiolated methyltin. Lead in stearates can leach into food when exposed to acids or fats. Colorants: Colorants are used to give plastics various colors, including organic and inorganic dyes. Lubricants: Lubricants are used during plastic processing to prevent sticking to the mold and to give the plastic surface a smooth and attractive appearance; stearic acid and paraffin are commonly used. The heavy metals in the aforementioned colorants and lubricants can cause chronic poisoning and organ damage, while the organic dyes in the colorants have sensitizing and carcinogenic effects. Plastic products used in food have an “identity card”; not many plastics are suitable for contact with food. According to regulations, the bottom of plastic containers used for food should carry such an “identity card”, in the form of a number – ranging from 1 to 7 – with each number representing a different type of plastic material. No. 1: Polyethylene (PE), formed from the aggregation of ethylene. It is commonly used for mineral water bottles, cola bottles, juice bottles, etc. Since it can only withstand temperatures of 70°C, it is only suitable for holding cold and warm beverages; it will deform if used to hold hot liquids or if heated. No. 2: High-density polyethylene (HDPE), suitable for bottles used to store food and medicines, containers for cleaning products and bath items, shopping bags, and trash bins. No. 3: Polyvinyl chloride (PVC), formed by the polymerization of vinyl chloride. Polyvinyl chloride plastic exposed to high temperatures and in contact with oils is prone to releasing phthalates and toxic, incompletely polymerized vinyl chloride monomers. Plastic wrap made of polyvinyl chloride is transparent, not easy to break, has strong adhesion, and is inexpensive; the film that sticks tightly to the boxes we see in supermarkets and hypermarkets is of this type. Due to its properties, it is only suitable for refrigerating and preserving vegetables and fruits; it is not appropriate for storing foods with high fat content such as meat and cakes, nor can it be used for heating in a microwave oven. No. 4: Low-density polyethylene (LDPE) plastic film and plastic wrap, which have good water resistance; therefore, it is used as an inner lining film in packaging such as paper milk cartons and beverage containers. Since low-density polyethylene plastic wrap melts at temperatures above 110°C, if this type of wrap is used to cover food that is being heated, the fats in the food will cause certain components of the plastic wrap to melt. Therefore, it is necessary to remove the plastic wrap before putting the food in the microwave; in any case, the food should not come into direct contact with the plastic wrap. Low-density polyethylene does not possess degradation properties on its own, and it is precisely this material that current plastic restrictions are aimed at limiting. No. 5: Polypropylene (PP), which is produced by polymerizing propylene; it has better transparency than polyethylene and is harder than it. Most of the boxes used for packaging in restaurants are made of this material, and plastic containers made from it can be heated in a microwave oven. No. 6: Polystyrene (PS), made by polymerizing styrene, is commonly used in bowls for instant noodles and fast-food containers. It is resistant to both heat and cold, but it releases harmful substances at very high temperatures; therefore, do not use it to heat instant noodles in the microwave, and try not to use it for hot foods. It should also not be used to hold strongly acidic substances (such as juice) or strongly alkaline substances, as this will cause the release of styrene and other components. No. 7: Polycarbonate (PC), which is synthesized using bisphenol A and diphenyl carbonate as raw materials, possesses excellent impact toughness and mechanical strength, as well as high transparency; hence it is known as the \"transparent metal\". It is commonly used to manufacture kettles, water cups, baby bottles, etc. During the production of PC, the raw material bisphenol A should be completely incorporated into the plastic structure and should not be released during use; however, this is often not achievable, and a small amount of bisphenol A fails to be fully converted into the plastic, and can be released into food when exposed to heat. Bisphenol A is an endocrine disruptor that is particularly harmful to developing fetuses and children, and may cause miscarriages, congenital intellectual disabilities, and delayed intellectual development in infants and young children. Some studies have also shown that bisphenol A can interfere with and antagonize thyroid hormones as well as inhibit the secretion of certain hormones, affecting male sexual development and hindering sperm formation, which may thus impact fertility. Therefore, extra care should be taken when using them, including baby bottles made of polycarbonate, to avoid harming the infant’s sexual development. In addition, melamine plastic, which is not among the above 7 types of plastics, is also commonly used as tableware by residents, restaurants, and office canteens. It is a thermosetting plastic frequently used to manufacture tableware such as bowls, plates, chopsticks, and spoons. It is made from melamine and formaldehyde resin as the main raw materials, along with an appropriate amount of cellulose filler and auxiliary materials such as colorants. It has a texture and feel similar to porcelain, is resistant to both acids and alkalis, boasts high surface hardness and impact resistance, and has a long service life. It can be cleaned and disinfected in a dishwasher at temperatures below 120°C. For tableware of the same size and thickness, melamine tableware is lighter than porcelain tableware, yet it is not as fragile as porcelain; therefore, it is particularly popular among parents of infants and young children. Due to the special molecular structure of melamine plastic, it is not suitable for use in microwave ovens, as it is prone to cracking. In melamine tableware, if the melamine is not fully polymerized, some of it can leach into the food. The market has seen the discovery of \"melamine tableware\" made from urea-formaldehyde resin or phenol-formaldehyde resin; it resembles genuine melamine tableware in appearance, making it difficult for ordinary people to distinguish between the two. However, such products contain high levels of formaldehyde, which is released more easily when heated or after holding \"hot\" food. Therefore, it is advisable to purchase genuine melamine tableware produced by reputable manufacturers from official stores. This post was last edited by QXZ-1966 on 2008-11-28 09:26]