Microplastic contamination in pre-rolled joints

Is your pre-roll milling solution causing microplastic contamination?

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:

• Safe to operate, clean, and service

• All stainless steel

• Adjustable mill size capability

• Example Mobius brand M210 Cannabis mill

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.

Note acceptable applications for whip style mills:

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

Photos of degraded 'whips' below