Is there a recognised definition of ‘Microplastics’ ?

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MichaelG.
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Is there a recognised definition of ‘Microplastics’ ?

#1 Post by MichaelG. » Wed Dec 04, 2019 11:22 pm

I have just read this, from Fox News

https://www.foxnews.com/science/oceans- ... e-realized

and I am utterly bemused.

How can quantitative surveys of ‘Microplastics’ have any credibility ?

MichaelG.
.

Note: The published paper is available via the link in the ‘News’ report.
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wporter
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Re: Is there a recognised definition of ‘Microplastics’ ?

#2 Post by wporter » Thu Dec 05, 2019 12:35 am

"How can quantitative surveys of ‘Microplastics’ have any credibility ?"

Why not?

When you read a simplistic summary of research in the popular press, sometimes it makes no sense. You will have to read the journal article to understand the constraints and methodologies involved, and to understand the conclusions. You certainly won't get any of that from Fox News.

MichaelG.
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Re: Is there a recognised definition of ‘Microplastics’ ?

#3 Post by MichaelG. » Thu Dec 05, 2019 9:17 am

wporter wrote:
Thu Dec 05, 2019 12:35 am
When you read a simplistic summary of research in the popular press, sometimes it makes no sense. You will have to read the journal article to understand the constraints and methodologies involved, and to understand the conclusions. You certainly won't get any of that from Fox News.
Yes, I am aware of that ... which is why I downloaded the paper.

However sensationalised the ‘Fox News’ summary might be ... there is a simple underlying fact stated by Brandon et al
Abstract
Microplastics (< 5 mm) have long been a concern in marine debris research, but quantifying the smallest microplastics (< 333 μm) has been hampered by appropriate collection methods, like net tows. We modified standard epifluorescence microscopy methods to develop a new technique to enumerate < 333 μm microplastics (mini-microplastics) from filtered surface seawater samples and salp stomach contents. This permitted us to distinguish mini-microplastics from phytoplankton and suspended particles. […]


My bemusement was due to the revelation that they found it necessary and appropriate to define a new sub-category of mini-microplastics [sic] when I had previously assumed that the existing broad definition of microplastics as particles less than 5mm meant what it said !!

It now appears that in much of previous research it meant “less than 5mm but greater than 333 μm”

I find that shocking

MichaelG.
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Hobbyst46
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Re: Is there a recognised definition of ‘Microplastics’ ?

#4 Post by Hobbyst46 » Thu Dec 05, 2019 9:27 am

MichaelG wrote:...
Thanks for posting this, Michael. I find the fluorescence analysis of tiny particles interesting.

Edit:
The classification by the original researchers of particles as <5mm, <333 um in the Introduction section of their article seems indeed to me non-decisive.
However, their aim is clearly defined. Citation:

"We aimed to isolate, identify, and quantify microplastics 5–333 μm in size, a subgroup of microplastics which we termed mini-microplastic."
I think that the "key" number of 333 um is based on a popular standard mesh size of the tow net.

The main challenge in that research was discrimination between plastics and other collected particles from the sea water according to fluorescence at different wavelengths. A fairly intriguing topic IMHO; and may I suggest, that at least some fun experiments along that line can be performed by hobbyists who own fluorescence microscopes, a boat and plankton nets, and a lot of spare time... (Bob ? ;) )

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Re: Is there a recognised definition of ‘Microplastics’ ?

#5 Post by MicroBob » Thu Dec 05, 2019 3:00 pm

Hi together,
the collection of particles between 333µm and 5mm really is not useful to determine the scope of the micro plastic problem.
There may have been a cause for this selective fishing: Most plancton is below 333µm and one avoids a net full of algae and protozoa with a few plastic particles in between.
In my view smaller particles will be more likely to be eaten by us and do harm.

I will put this on my to-do list for fluorescence microscopy. It would be a good test to create micro plastic from specific plastics and check whether they can be identified by their fluorescence. With FIJI it might pe possible to count them in an image.

Bob

MichaelG.
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Re: Is there a recognised definition of ‘Microplastics’ ?

#6 Post by MichaelG. » Thu Dec 05, 2019 5:32 pm

Hobbyst46 wrote:
Thu Dec 05, 2019 9:27 am
Citation:

"We aimed to isolate, identify, and quantify microplastics 5–333 μm in size, a subgroup of microplastics which we termed mini-microplastic."
I think that the "key" number of 333 um is based on a popular standard mesh size of the tow net.
Agreed ... I think that much is clear

Perhaps I expressed my initial thoughts poorly, but my concern is that; in the light of this paper, it appears that many previous studies are invalidated [assuming that the definition of microplastic was plastic particles of less than 5mm] ... Which is why I asked the question.

MichaelG.

.

Edit: according to Wikipedia, the definition is attributable to NOAA
Microplastics are very small pieces of plastic that pollute the environment.[1] Microplastics are not a specific kind of plastic, but rather any type of plastic fragment that is less than 5 mm in length according to the U.S. National Oceanic and Atmospheric Administration (NOAA).[2][3] They enter natural ecosystems from a variety of sources, including cosmetics, clothing, and industrial processes.
Ref. https://en.wikipedia.org/wiki/Microplastics

... and I note this, from page 10 of reference [2]
While there is no requirement for a “lower bound” in size, as a practical matter defining microplastics as those that range between 5mm and 333μm recognizes the common use of 333μm mesh neuston nets commonly used in the field to capture plankton and floating debris.
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Re: Is there a recognised definition of ‘Microplastics’ ?

#7 Post by MichaelG. » Fri Apr 01, 2022 8:47 am

I am reviving this thread because I have just read a brief article from the Smithsonian:
https://www.smithsonianmag.com/smart-ne ... 180979826/

At last … someone is including the very small in their investigations

MichaelG.
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apochronaut
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Re: Is there a recognised definition of ‘Microplastics’ ?

#8 Post by apochronaut » Fri Apr 01, 2022 9:29 am

A T.V. evangelist with a ring as big as the Lincoln he was driving, pulled in the farm lane one summer day and I can't remember why he was there. Directions maybe? He was there long enough for me to find out that he had plastic in his blood!

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Re: Is there a recognised definition of ‘Microplastics’ ?

#9 Post by crb5 » Fri Apr 01, 2022 10:56 pm

There is still no agreed definition of micro- and nano-plastics. In a recent paper from Richard Thompson (a father figure in the field), he opens with a statement “Microplastics (nominally < 5 mm (Arthur et al., 2009)) and nanoplastics (<1 µm (Kershaw, 2015) or < 0.1 µm (Chain, 2016) depending on the definition used) can be directly released into the environment or formed from the degradation of larger plastic items (Koelmans et al., 2015).”

https://www.sciencedirect.com/science/a ... via%3Dihub

Others have argued that the microplastics definition should range from 1 to 1,000 µm (i.e. 1 mm) rather than the arbitrary 5 mm which I believe was reached by considering particles below which are likely need some kind of lens to see them well enough to judge their plastic origins.

The lower cut-off limit is obviously affected by the collection method (net mesh or filtration pore size) and has been explored systematically:

https://www.researchgate.net/publicatio ... _mesh-size

To add to the problems, many microplastics found in the environment are fibers which may or may not be trapped by a mesh when the length exceeds the mesh size but the diameter doesn’t.

The lower limit is also challenged by the sensitivity of the detection method. Here fluorescence is one of the best and is capable of detecting the nanoplastic regime however this limit is defined. But fluorescence does not identify specific chemistry (unlike Raman and IR spectroscopy) and is subject to false positives and false negatives. In the paper which initiated this thread (Brandon et al 2019, https://aslopubs.onlinelibrary.wiley.co ... lol2.10127 ), the authors used intrinsic fluorescence found in many plastics but not all. The fluorescent is likely to arise from additives, since the basic polymer backbones of plastics are unlikely to have any emission at visible wavelengths. Furthermore, any strongly colored plastic is likely to quench the emission from other components, so brightfield inspection is also required. Nile Red dye has been widely used to increase the detection limit (and to some extent the specificity) of microplastics using fluorescence https://pubs.acs.org/doi/full/10.1021/acs.est.7b04512

But the good news is that you don’t need a dedicated fluorescence microscope to see microplastic fluorescence. Practically any microscope can be adapted. https://sites.google.com/ucsc.edu/cbags ... roplastics.

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Re: Is there a recognised definition of ‘Microplastics’ ?

#10 Post by MichaelG. » Sat Apr 02, 2022 8:35 am

crb5 wrote:
Fri Apr 01, 2022 10:56 pm
There is still no agreed definition of micro- and nano-plastics. In a recent paper from Richard Thompson (a father figure in the field), he opens with a statement “Microplastics (nominally < 5 mm (Arthur et al., 2009)) and nanoplastics (<1 µm (Kershaw, 2015) or < 0.1 µm (Chain, 2016) depending on the definition used) can be directly released into the environment or formed from the degradation of larger plastic items (Koelmans et al., 2015).”

https://www.sciencedirect.com/science/a ... via%3Dihub

[…]
.

Thanks for all the useful links and comments … But that was basically what prompted my original question.
“Microplastics (nominally < 5 mm (Arthur et al., 2009)”
seemed a clear and logical definition … until people started messing with it

MichaelG.
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Hobbyst46
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Re: Is there a recognised definition of ‘Microplastics’ ?

#11 Post by Hobbyst46 » Sat Apr 02, 2022 9:47 am

@MichaelG

@crb5

Having read the Labbe and Begshaw article in the link, it seems to me that the size of microplastics should be defined by the detection mode. Thus, the authors modified a stereo microscope and a compound microscope for fluorescence; the compound objective seems to be 10X. Using higher mag objectives would be limited by the working distance, because of the top-sideways excitation illumination. It would be difficult to achieve excitation for a 40X objective for example, given that the authors strive for the most affordable adaptation of an affordable microscope. In fact, the authors state that a chief advantage of their configurations over "competitors" is low cost. This is understandable since their configuration does not include expensive interference filters (especially the dichroic mirror) and cubes.

So, IMO, for hobby detection of micro-plastic by fluorescence, according to those modifications of microscopes, the lower size limit should be determined by the smallest fluorescing spot that can be viewed with a 10X objective of a respectable working distance (say).

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Re: Is there a recognised definition of ‘Microplastics’ ?

#12 Post by crb5 » Sat Apr 02, 2022 5:52 pm

@ Hobbyst46

I agree any report about the number of microplastic particles in a given sample volume should be accompanied by a statement regarding the size range that can be captured by the net/filter or positively identified, which ever is the larger. The “problem” with fluorescence is that it can be detected with good sensitivity, even below the conventional resolution limit of the objective lens, but knowing whether it is really plastic remains a challenge. In the Labbe et al paper, we used a 20 um net mesh for collection and particles around this size could reasonably be distinguished from biologically-derived material by the lack of cellular structure. But any fluorescently-stained particles smaller than this remained ambiguous.

@ Hobbyst46. You are right that LED flashlight/torch illumination from the side requires a reasonable working distance and limits the objective to around 10x, but a focused beam from a laser pointer allows fluorescence excitation from the side with a 40x objective, as described in the Supporting Information III of Labbe et al.

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Re: Is there a recognised definition of ‘Microplastics’ ?

#13 Post by Hobbyst46 » Sat Apr 02, 2022 7:24 pm

crb5 wrote:
Sat Apr 02, 2022 5:52 pm
... a focused beam from a laser pointer allows fluorescence excitation from the side with a 40x objective, as described in the Supporting Information III of Labbe et al.
Thanks ! It seems that I somehow missed important details in the SI.

I'm trying to avoid laser devices at home, because of possible unnoticed spurious reflections. A 5mm super-bright LED can shine directly into the side of the slide and yield reflections and refractions from a transparent object. Will probably be too weak to be a fluorescence excitation source.

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Re: Is there a recognised definition of ‘Microplastics’ ?

#14 Post by MichaelG. » Sun Jun 25, 2023 7:24 am

I am resurrecting this old thread, because the topic is still [increasingly] relevant:

I was rather disappointed by the de-facto definition of ‘microplastic’ but I am encouraged by finding this recent paper:
https://www.mdpi.com/2673-8929/1/3/24

Recommended reading !

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apochronaut
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Re: Is there a recognised definition of ‘Microplastics’ ?

#15 Post by apochronaut » Sun Jun 25, 2023 1:29 pm

Microsplastics cross the blood brain barrier. It seems Polythene Pam was a real person.

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Re: Is there a recognised definition of ‘Microplastics’ ?

#16 Post by Dennis » Thu Jun 29, 2023 8:58 pm

While not exactly plastic (I guess), there is another problematic-

PFAS is short for perfloroalky and polyfuoroalkyl substances which include chemicals known as PFOS, PFOA and GenX. The report refers to them as “forever chemicals” because they don't break down once they're in the environment. They've been manufactured since the 1940s for their ability to repel oil and water.

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Re: Is there a recognised definition of ‘Microplastics’ ?

#17 Post by PeteM » Thu Jun 29, 2023 9:12 pm

apochronaut wrote:
Sun Jun 25, 2023 1:29 pm
Microsplastics cross the blood brain barrier. It seems Polythene Pam was a real person.
Yikes. And I thought the now-ambiguously-defined "neuroplasticity" into old age was a good thing. Now comes this:

https://www.sustainability-times.com/gr ... d-barrier/

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