How Small is Small?

This week I realized that I've never given a measurement for microplastics that makes sense to the average reader. I talk all about micrometer-sized objects, but it is unlikely that the average individual knows how small a micrometer is; and for those who know the theoretical size of a micrometer, it is unlikely that they know the comparative size of a micrometer. Therefore, I want to spend time making the size of microplastics a comparative measurement, rather than a theoretical one. Below are some images from my research; the blue object that you can see is a microfragment, while the red is a microfiber. Ignore the two black items: one is the pencil line I drew for measuring the particles, while the other is a contaminant. The microfiber is 3.017 mm in length, which is likely not a foreign measurement. However, the microfragment is 0.325 mm--or 325 micrometers--which may be more abstract.
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Let's compare these objects to ones that we encounter daily. For example, the diameter of a penny is over 19,000 micrometers, while the length of a staple is 6,000 micrometers--just outside the range of microplastic size. On the other hand, the head of a pin is 2,540 micrometers in diameter and the point of an average pin is approximately 127 micrometers, so both are well within the microplastic size range of 1 micrometer to 5 mm (5,000 micrometers). However, I think the item that most people are familiar with that is within the microplastic size range is human hair. The diameter of a single human hair ranges between 17 and 180 micrometers, but looking at a single hair follicle and estimating that width is insane to think about. Similarly, identifying the size of a single microplastic is incredibly challenging without microscope assistance. Although some may range on the large end of the size spectrum and can be seen without assistance, most of the particles that I am working with are closer in size to the microfragment.

The incredibly small size of these particles are just part of the reason that they are so challenging to study and come up with effective management strategies for. Scientists collecting water column samples using drag nets may be using nets that have mesh sizes far too large for these particles, and sediment sampling may contain so many microplastics that it becomes a challenge to analyze every single particle. I am lucky that while there are many particles for me to assess in my own sampling, I have not been inundated with items to identify, which gives me hope that perhaps we have overestimated the abundances of plastics in the ocean (though that hope is not supported by a plethora of studies).

In separate news, as the semester starts back up in a little over a week's time, I may be changing my weekly blog post to Tuesdays or Thursdays to work around my schedule. Next week I will know for sure and will let you know. Thanks for tuning in!

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