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Writer's pictureMatthew Grabowski

Microplastic contamination in pre-rolled joints

Updated: Apr 22, 2023

Is your pre-roll milling solution causing microplastic contamination?


Context:

When you get a pre-rolled joint how do you know what is inside of it? What if a manufacturing equipment oversight caused tiny bits of plastic to wind up inside the joint you are about to smoke?


The rapper Camron said it best in the 2003 song ‘Purple Haze’


“[Cam - talking]

I gotta come in now, I don't know what Tito's rolling up

I gotta roll it myself up , I don't know what's in them Dutch Masters

If you don't crush your own weed up

And put it in the blunt yourself

Your own brother'll hand you some dust

That's what time it is”


Definitions for the purpose of this article:
  • Mill is a machine used to grind cannabis biomass to a desired size in preparation for filling pre-rolled joints.

  • The term whip style mills refers to plastic strings spun inside a cylinder as the grinding mechanism.

  • Whips are the plastic stings used in the whip style mill. The whips function in the same way plastic string on a weed-wacker does.

What is the problem?

During normal use plastic whips inside the mill wear. This wear causes the release of microplastic particles into the milled cannabis used to fill pre-rolls. See photos of whip degradation below.


Who does this concern?

Cannabis consumer product manufacturers (pre-roll manufacturers) using whip style mills and whip mill manufacturers.


When does this issue occur?

During normal operation of the mill (grinder). The plastic whips used by the mill break down slowly. The speed of whip degradation will be influenced by factors like moisture content of the biomass, and stem thickness.


Why use a whip style mill?

Answer; cost and oversight. The mills that cause this plastic contamination are a common and cheap milling solution. The cost of a whip style mill is ~80% less than a proper stainless mill.


What type of plastic do you prefer to smoke?

Manufacturers of whip style mills sell replacement whips. One popular brand sells ‘food grade plastic’ whips in addition to ‘commercial grade’ whips.


Proper pre-roll mill qualifications:
Conclusion:

Whip mills are not capable of producing contaminant free milled cannabis suitable for pre-rolled joints.


Solution:

Use a proper mill. Pair it with comprehensive standard operating procedures, preventative maintenance, and inspection protocols. As a final step, use metal detector compatible packaging, and scan all finished products with a detector.


Acceptable applications for whip style mills:

Milling for extraction when using hydrocarbon, ethanol, or CO2 as a solvent. Plastic particulate from whips in the biomass will not be dissolved by these solvents.


Photos of degraded 'whips' below





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