Contaminants

Contaminants are unwanted substances that can enter a hemp product during growing, extraction, manufacturing or storage and that laboratories screen for.

The main classes are pesticides applied to or drifting onto crops, heavy metals such as lead, arsenic, cadmium and mercury that hemp readily absorbs from soil, residual solvents left over from extraction, microbes including molds, yeast, Salmonella and E. coli, and mycotoxins such as aflatoxin produced by mold. Each class is tested with a different method: chromatography coupled to mass spectrometry for pesticides and solvents, inductively coupled plasma mass spectrometry for metals, and culture or DNA-based methods for microbes.

A certificate of analysis lists each contaminant panel with the laboratory's action limit and the measured result, and a product passes when every analyte falls below its limit. Because federal rules for finished hemp products are still developing, action limits are usually borrowed from state cannabis programs or pharmacopeial standards and can differ between laboratories. Readers comparing certificates should check which panels were run and against which limits.