Wrapping it Up
The truth about plastic wrap processing and safety
Heidi L. Obidzinski
Recent media exposure has turned plastic wrap into a kitchen hazard, giving the symptoms of overexposure to plasticizers as cancer and infertility. Outraged scientists have claimed that any such reports of unsafe qualities of plastic wrap are scientifically unsound and a result of overzealous environmentalist gibberish. This research report will recite various sources that will show the unstability of reports by the media when compared to the well researched evidence of experts in the scientific field.
The manufacture of plastic wrap is a quite interesting process. It all starts with a process called extrusion. Extrusion is a word that originates from Greek roots meaning to push out. The process of extrusion can best be illustrated by the function of a hot glue gun [1]. Plastic material is fed into the gun, heated and forced out through a hole, which gives it shape. For plastic wrap, a plastic material is loaded into the extruder through a hopper, which is like a funnel, that directs the material through a hole in the top of the extruder called the feed throat. All plasticizers and additives are added along with the plastic and are mixed within the extruder by means of the extruder screw. The material is propelled forward by the rotating motion of the extruder screw. The material is heated by friction and heaters in the barrel of the extruder. As the melted material exits the barrel it is forced through a die. The die is tubular and consists of an offset die and a pipe die which turns the material upwards. An air intake is through the middle of the die vertically and the material flows around it forming a hollow cylinder. Flowing the material upwards allows for a uniform distribution of gravity. If the flow were directed downward a lot more room would be required for this process because the gravity would further extend the material. It would be impractical and too much space would be consumed in a downward extrusion process using conventional equipment. The material is run through a cooling ring so that the material gains stability, but still maintains flexibility. After this cooling ring, air is blown into the material through the air intake discussed earlier. The plastic is inflated like a balloon. As the material expands, it cools and crystallized. The balloon is carefully guided by a sizing basket or external air chamber to avoid over stretching. The bubble, then fully cooled, is collapsed by being drawn through a triangular guide, called a collapsing guide, and rolled flat through nip rolls. The nip rolls also accomplish vertical orientation of the polymer chains by pulling it forward as it is fed through the rollers. The inflation of the plastic into a bubble accomplishes a horizontal orientation of the polymer chains. Therefore, plastic wrap is biaxially oriented. The film as a result is also semi-crystallized. The film is slit and rolled for packaging and shipment.
Plastic wrap is a necessity for food packaging in this day. It protects our food against countless bacteria, keeps it fresh and free from contamination. It is hardly disputed that without plastic wrap there would be a lot more disease and infection due to tainted food. So what is all of the commotion heard recently in the media?
The most popular plastic wraps are made from low-density polyethylene (LDPE) or polyvinyl chloride (PVC). The most controversy has been over plastic wrap made from polyvinyl chloride (the same material used for water pipes and shower curtains). The phthalate di(2-ethylhexyl) adipate (DEHA) is a plasticizer added to polyvinyl chloride based plastic wraps. DEHA has been accused of causing cancer, teratogenic effects, immunotoxicity, neurotoxicity, gene mutations, liver, kidney, reproductive, developmental toxicity or other serious or irreversible chronic health effects [2].
DEHA is used to make the plastic more flexible and to "stick". The plastic’s adherence to itself is what keeps the air out. A tight sel is desirable to expand the life span of perishable food and keep microscopic bacteria and germs out of food.
Plasticizers are accused of being endocrine disrupters [3]. Endocrine disrupters interrupt the natural hormonal process of the body by mimicking complete interference. Endocrine disrupters are suspected to cause breast cancer, birth defects, low sperm count and mental problems. Plasticizers can leach out of plastic and into food, especially with a high fat content (i.e., cheese and meat). One report claims to have found an especially high level of DEHA in food tested [3]. The study wrapped cheese with 19 different polyvinyl chloride wraps. They found in the cheese DEHA levels from 51 to 270 parts per million, the average being 153. This is considered to be a large amount, because Europe has limited the DEHA content of plastic wrap to 18 parts per million. The article says that a maximum daily dosage for a 40 pound child would be exceeded by consuming 1 and a half ounces of this cheese, and 4 ounces for a 130 pound adult. They reference Consumer Reports for supporting their findings, but Consumer Reports findings came out inconclusive [4].
The most concern has been expressed in the microwave capacity of plastic wrap. The Consumer Reports did a study of wrapping cooked hamburgers in plastic wrap and heating them in the microwave. Half they wrapped the burger on a plate in plastic and the other half they placed in a bowl and wrapped in plastic. For the burgers wrapped on the plate, only a minimal amount of plasticizer was found. Similarly, for the burgers wrapped in a bowl, there was no plasticizer found.
CMA Phthalate Esters Panel has responded to several media accusations on the harmful effects of DEHA [5]. They reference the SIDS Initial Assessment Report (SIAR) [6] which was approved by scientists who made the recommendation that no further testing was required. The report concluded that there was little risk to humans from eating foods in contact with cling wrap. They also attest that the EPA has removed DEHA from their list of toxic chemicals, which is maintained by the federal Emergency Planning and Community Right-to-Know Act (EPCRA). The EPA has also placed DEHA in Group C (possible human carcinogens). The National Toxicology Program, after conducting 90-day lifetime feeding studies on rats, found it does not cause tumors in them. The International Agency for Research on Cancer has put DEHA in Group 3, which also contains caffiene and tea. The tests they quote reveal that a dose of 1080 mg/kg/day, or 12,000 parts per million of food, leads to only a weak response in lab rats. This means that a 155 pound adult would have to eat an amount of DEHA equivalent to the size of a hamburger patty (75.6 grams) to see any kind of effect. Further, rats fed 1500 mg/kg/day of DEHA still had no effects to their reproductive organs. This is equivalent to a 155 pound adult eating a quarter-pound of DEHA.
The American Plastics council adds that the lowest-observed-adverse-effect-level (LOAEL) in laboratory animals is 1080 mg/kg/day [7]. This would mean that a 150 pound adult would have to eat 1,000 pounds of cheese wrapped in plastic containing DEHA every day.
An article in the Wall Street Journal by Michael Fumento [8] points out that the people at greatest risk to exposure of plasticizers are dialysis patients, who have their blood carried by plastic tubes and filtered through a machine. These individuals have only one-eighth of the exposure which has been proven safe in laboratory animals. In fact many medical equipment is made of polyvinyl chloride and thus contains plasticizers (i.e., IV bags, blood administration sets and dialysis tubing). He further comments that this whole scare was started by the Greenpeace war against chlorine-based chemicals. What people fail to realize is how many daily and necessary items are all made from polyvinyl chloride containing plasticizers, and how much trouble we would all be in if they were suddenly abandoned.
Plastic wrap is a safe substance. The most leakage occurs when they are put into a microwave. The best way to remain safe is to use common sense, when using plastic wrap in the microwave, do not let it touch the food. Only use food wraps in the microwave that specifically say that they are microwave safe. If using a plastic wrap that contains a plasticizer bothers you, than use a polyethylene based plastic wrap, which is plasticizer free [4]. If plastic wrap melts on your food "you’ll likely have an unpleasant eating experience - but you won’t be harmed" [9].
References
1. Strong, A.B., "Plastics Materials and Processing"; Prentice Hall, 1996, p. 257-293.