The Right Chemistry: Blanket bans on plastic packaging are unrealistic



A cucumber that is discarded because of spoilage has the environmental impact of 93 plastic wraps.

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Trying to separate sense from nonsense for over four decades is quite an educational experience. I have learned a great deal, but perhaps the lesson at the top of the pile is that once you start scratching the surface of an issue, it invariably gets more complicated than it first seems. Rarely are issues black or white, they are various shades of grey. That is the case whether we are talking about electric vehicles, food additives, nutrition, cholesterol, medications, vaccination, climate change, insecticides, herbicides, personal care products, dietary supplements, space exploration, history or plastics. Ahhh, plastics. They have become villains, the targets of emotional attacks by various bloggers who want plastics banned.

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Let’s get the nonsense out of the way. If you are going to ban plastics, you can forget about airplanes, cars, computers, cell phones and you can close down hospitals. Obviously banning plastics is an absurd idea. However, given the deluge of plastic garbage, the frightening notion of microplastics building up in the oceans and possibly in our bodies, we have to engage in a risk-benefit analysis for specific applications. It is unreasonable to question the use of plastics in a heart-lung machine or in a surgical mask, but an English cucumber shrink wrapped in plastic is a different story. Or is it?

The French government thinks it is different, and since Jan. 1, cucumbers wrapped in plastic can no longer be sold. The plastic ban does not only apply to cucumbers, but to many other fruits and vegetables as well, with some exceptions. Cut fruit and some delicate produce such as peaches, berries and cherry tomatoes can still be sold in plastic for now. By the end of June 2023, however, plastic packaging will also be banned for cherry tomatoes, green beans and peaches, and by the end of 2024, such packaging must also be removed from asparagus, mushrooms, cherries and some salads and herbs. Finally, by the end of 2026, all berries will have to be sold without plastic packaging. Sounds like a great idea, and it mostly is. But not in every case. Such as English shrink-wrapped cucumbers, in which case the benefits likely outweigh the risks.

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Let’s first look at the science of “shrink-wrapping,” a technology introduced in the 1960s. There are several different materials that can be used, the common feature being that they are all polymers. Thin films of polyvinyl chloride (PVC), polypropylene or polyethylene can all be shrunk, with polyethylene being used the most widely. Picture a chain made of paper clips linked together. Each clip represents an ethylene molecule and the chain is polyethylene. If you now drop the chain into your hand so that you can close your fist around it, it will coil more or less into a ball. A film of polyethylene is made of many such coils packed together. If this film is now stretched, the balls uncoil to form more or less straight chains that are maintained in this position by the small attractive forces that occur between atoms in adjacent chains. Nature, however, prefers randomness over orderliness and if heat is now applied, the molecules become more vigorous, overcome the attraction between adjacent chains, which then proceed to coil again. The macroscopic effect here is that the film shrinks to fit snuggly around any object, be it a jar of tomato sauce, a medicine bottle or a cucumber.

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Why would a cucumber be shrink-wrapped? No producer has ever said “We are not spending enough on our product, so let’s increase our expenses by wrapping it in useless environmentally unfriendly plastic.” The fact is that shrink-wrapping a cucumbers can extend its shelf life by some 60 per cent. There are several reasons for this. The wrap dramatically reduces moisture loss and prevents shrivelling. It also reduces contact with oxygen in the air and therefore the rate of respiration. Fruits and vegetables continue to respire after being picked, meaning that their carbohydrate content reacts with oxygen to produce carbon dioxide and water, resulting in a change of texture. Oxidation is also responsible for other chemical changes that can affect nutrition. For example, shrink-wrapped broccoli loses far less of the glucosinolates thought to be responsible for the vegetable’s health benefits than loose broccoli.

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Produce that is damaged by moisture loss or oxidation ends up being discarded. It is estimated that about one-third of all food produced is wasted! The production and transportation involved in food that will never be used and the wasted agrochemicals leave a huge environmental footprint. Of course, plastic production also has an environmental impact, but it turns out that at least for cucumbers, the plastic wrap is responsible only for one per cent of that impact. A cucumber that is discarded because of spoilage has the environmental impact of 93 plastic wraps. A cradle-to-grave analysis by the Swiss Federal Laboratories for Materials Science and Technology has concluded that unwrapped cucumbers have a five times greater negative impact on the environment than shrink-wrapped ones.

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Furthermore, the polyethylene used in shrink wraps can be recycled. It can also be made from ethylene derived from ethanol produced from sugar cane with a reduced environmental impact, because the sugar cane absorbs carbon dioxide from the air as it grows. Compostable polylactic acid derived from corn can also be used for wraps, although it is more expensive.

All of this is to suggest that blanket bans on plastic packaging are unrealistic and decisions have to be made on specific applications that take into account possible contamination from handling, nutritional losses and environmental impact. A quarter watermelon needs to be wrapped, but we can do without shrink wrapping a six pack of bottled water. Actually, we can even do without the bottled water.

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Joe Schwarcz is director of McGill University’s Office for Science & Society ( He hosts The Dr. Joe Show on CJAD Radio 800 AM every Sunday from 3 to 4 p.m.

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