It’s Microplastics All the Way Down

After my last column on how the simple act of playing with Lego bricks was able to generate microplastics, a reader reminded me of research published last fall, in which the researchers found that plastics recycling facilities were generators of microplastics. Cutting, grinding, and similar size-reduction operations are needed to fit the plastic into standard processing machines. Since there is little or no concern about capture of the microplastics, they can escape and make their way into the broader environment (both air and water).

Microplastics from Lego and recycling operations are both unusual sources as they start out as microplastics, but ones that are unintentionally formed. Let me bring in some terminology to help clarify this.

The role of intentionality.

Microplastics are often broken down into two categories — primary and secondary. Primary microplastics are plastics that start out as microplastics, such as the microbeads added to many cosmetic products. They are intentionally made as microplastics. In contrast, secondary microplastics start out as large pieces of plastic that become microplastics due to the environment breaking them into smaller pieces. This size reduction is mostly caused by photo-oxidation, but it can also happen from mechanical and biodegradation processes.

Related:Tire Wear a Major Source of Microplastics, Say Researchers

The microplastics from Lego activities and recycling facilities likely would qualify as primary microplastics: They start out small instead of big, even if this small size is not intended.

A misleading perspective.

This perspective of primary and secondary microplastics, however, can be quite misleading. With secondary microplastics, big pieces of plastic garbage become smaller pieces of plastic garbage and those smaller pieces of plastic garbage become ever smaller pieces of plastic garbage, and so on, without limit, until you get to atoms (which for all practical purposes are indestructible.)

That’s because the size degradation processes do not have a lower size limit at which they stop working. While I do suspect mechanical degradation becomes less impactful at smaller sizes, UV light will keep breaking down chemical bonds as long as two atoms are bound together, and bugs will more readily eat and degrade smaller molecules than larger ones. At some point, what’s left is so small that it isn’t even plastic anymore. Instead, it has changed into some other organic chemical(s).

A common fate.

Plastics become microplastics become nanoplastics become non-plastic. Microplastics right now — and to a lesser extent nanoplastics — are treated as a generic catch bucket, the end of the road for plastic pollution. But it isn’t — it’s just a stop along the way. While the distinction between primary and secondary microplastics might be useful in some cases, the fate of both categories is the same.

I’m not suggesting that we not worry about (micro)plastic pollution. I’m dead set against any plastic pollution anywhere. It’s just that I see the distinction between primary and secondary microplastics as deceptive and misleading. The degradation that forms secondary microplastics is something that never stops.

A question to ponder: How much microplastic or nanoplastic is “lost” like this, becoming non-plastic?