How We Designed Microplastics into our Diet

How We Designed Microplastics into our Diet

New research from the University of Newcastle in Australia suggests that we may be consuming up to five grams of plastic every week through our food, water, and perhaps even through the air we breathe. To put this into perspective, five grams is as much plastic as you might find in a credit card. It’s discomforting to imagine all of that plastic potentially stuck inside our lungs, stomach and intestinal tract. 

This thought came to mind last week when I was removing some fruit from the mesh bag that it had been packaged in. Looking down at my hands, I realised they were covered in small flecks of brightly coloured plastic. The bags were already beginning to shred into microplastic components. It doesn’t take much to imagine how tiny pieces of plastic like this could find their way back into the environment and then back into us. 

As we now fumble with how to approach solving this “wicked problem”, it is important to realise that the situation we find ourselves in is no accident, but actually the result of design. Nearly sixty years ago, a purposeful set of engineering and economic design choices were made which led us to this point. 

A good place to start the story is with one Gustaf Thulin Sten, an engineer working for the Celloplast company in Sweden. In the 1950s Celloplast was looking for new uses for its range of thin film plastics. A first patent from the company in 1959 described how to create, “tubing for packaging purposes.” Essentially, these were the first plastic bags on a roll. 

The innovation didn’t stop there. Sten was able to extend the design thinking. By selectively cutting out parts of the partially sealed tubes, he was able to create the world’s first plastic bag with handles. From a purely functional perspective, it is an elegant and ingenious solution. It takes a lightweight and durable material and creates an incredibly useful tool that amplifies human capability. The patent describes his invention as:

“A bag composed of a polymeric weldable sheet material in the form of a flattened tube… and having a spaced integral handle forming portions extending upwardly…” (From US Patent US3756300A)


Likewise, the plastic mesh (or net) bag also seems to have been around for quite a while. Although I managed to locate a 1973 US Patent for a “Plastic Mesh Bag,” it’s possible there were earlier patents. 

“A seamless plastic mesh bag is made from a melt of thermoplastic by forming an open mesh network of plastic strands terminating in a selvage of thickened cross-section and then stretching the mesh…” (From US Patent 3756300).

From: US Patent US3756300A

From: US Patent US3756300A

From an industry lens, they clearly fulfils key business and consumer needs. The bags are strong enough to carry kilograms of consumer goods. They last long enough to get into our home. They use only small amounts of material and can be made by automated machines. Their cost is miniscle compared to other packaging materials. Paraphrasing from one plastic mesh bag wholesaler: 

‘It’s the most relevant and most economic packaging type used for fruit, vegetable and food packaging. It prevents the product inside from infestation and decay by airing with its pores and enables the product inside to be exposed in the best way with its limitless colour options.’

Initially, demand for all types plastic bags was low. For centuries, paper, wood, fibre, cotton, hessian and other natural fibres had dominated the storage and transportation of goods and there was no real reason why this should change. The tipping point arrived in the mid 1980s when it became clear that the price of plastic bags had fallen significantly when compared to paper and retailers began offering both. In addition to cost savings, plastic bags held a number of other benefits; they were much stronger than paper, didn’t perish as easily and didn’t leak.

But even as plastic first began to find its place in the consumer marketplace, there were early environmental concerns. In an article in the Los Angeles Times in 1989, Barry Commoner, an environmentalist and the director of the Centre for Biology of Natural Systems at Queens College asked: 

“It raises the issue of public, democratic control of production decisions. In other words, does society really need plastic bags?”

In the same article, the Plastic Grocery Sack Council, formed by members of the plastics industry, rebutted the concerns, noting: 

“plastics present no leaching, bacterial or explosive gas problem.” 

Keep in mind, by 1989, the grocery sack market was worth USD600 million (not adjusted for inflation). There was a lot of money at stake. S. Edward Weary, speaking on behalf of the Plastic Grocery Sack Council noted: 

“What it boils down to is this…The consumer wants something that is strong, attractive and convenient. Our product [plastic bags] has it, theirs doesn’t.”

As plastic became more popular, the plastic bag began to dominate until it was the most common form of small goods packaging on the market, despite protests from both consumers (and the paper industry). 

Nearly thirty years later, in 2019, plastic bags have hit another cultural flashpoint as cities and even entire countries are banning their use. Admirable and crucial though the bans are, as the plastic bag is being pushed out of the marketplace, its more nebulous cousin, the plastic net bag, continues to unobtrusively package up fruits, vegetables and other goods for transportation and sale. 

As it has woven its way through industry (pun intended), the plastic mesh bag hasn’t attracted anywhere near the same level of attention as its continuously formed cousin. Perhaps, through its similar design to string bags, many of us don’t stop to think that it’s made of plastic.

Ironically, by being made of much weaker fibres, plastic mesh networks are far more frangible and liable to come apart into small fragments while still in use. I was curious, so I put some of the fibres I pulled off my hands and looked at them under a microscope. 

Microscope Plastic Photo by Christopher Roosen

Microscope Plastic Photo by Christopher Roosen

All of the broken fibres are of consistent size and shape and break off the bag in the same way. As the bag is flexed and moved, the plastic triangles that make up the interlocked mesh break at their middle; falling like plastic snow onto hands, counters and floors. The fragments are lightweight and sticky. They most likely end up being washed down the drain, in landfill, or carried elsewhere on our clothes and bodies. At this point they are large enough to pick up with tweezers. However, over time I suspect they will break down, enter our ecosystems and then our bodies. 

There isn’t anything that I could find on what Gustaf Thulin Sten felt about the impact of his plastic bag innovation. I also couldn’t find anything about the inventor of the ’Plastic Mesh Bag’, though its patent seems currently assigned to a large plastic net manufacturer in the United States. I by no means want to pick on the inventors alone. It was entirely likely they were focused on providing the best creative problem solving they could for the companies they worked for. 

On paper, disposable plastic and mesh bags both tick all the boxes when it came to meeting business and consumer needs from economic and functional standpoints, and they still do.  But when we take a wider systems-level perspective, one that looks at the materials that make up these bags, how they are produced, how they are used and how they are then disposed of, we begin to see a different story. When we look at their life cycle as a whole, we can see that the use of these mesh bags is not a good choice but a terrible one. We are now all paying a cost for this choice; with our health, the environment and our future.

It’s a reminder of a question we need to ask ourselves before designing or producing anything: have we really considered the wider system impact? If design choice got us into the plastic problem we now face, then we need to think carefully about how to more responsibly design our future, to get us out of it.


Kilvert, Nick (2019) Microplastics are probably in your diet. But should you be worried? Retrieved October 2019 from: https://www.abc.net.au/news/science/2019-09-17/microplastics-diet-health-bottled-water/11478530 

Laskow, Sarah (2014) How the Plastic Bag Became So Popular. Retrieved, October 2019 from: https://www.theatlantic.com/technology/archive/2014/10/how-the-plastic-bag-became-so-popular/381065/ 

Nalle, G. (1971) Plastic Mesh Bag. Retrieved October 2019, from https://patents.google.com/patent/US3180557 

Thulin Sten, Gustaf. (1962) Bag with handle of weldable plastic material. Retrieved October 2019 from https://patents.google.com/patent/US3756300A/ 

Wikipedia, Plastic Bag. Retreieved October 2019, from https://en.wikipedia.org/wiki/Plastic_bag

Microscope Plastic Photo (c) 2019 Christopher Roosen

Plastic Tweezers Photo (c) 2019 Christopher Roosen

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