Concentrates issue: Testing for residual solvents
What isn't in your concentrates is just as important as what is
By Analytical 360 Chief Science Officer Randall Oliver & Chief Operating Officer Edward Stremlow
Lab-tested Cannabis has become common in Washington with the maturing medical marijuana industry and the passage of I-502. Cultivators, processors and access points have begun to use Cannabis testing to develop, refine and ensure consistency and quality in their products. Fueled by a demand from patients, cannabinoid profiling has led the charge in the industry.
However, with increasingly educated and demanding patients, and looming state regulation, medical marijuana has begun the transformation of adding safety into the growing equation.
With a strong patient demand for refined Cannabis extractions, questions about safety are becoming as common as questions about potency. Patients want to know which products are safe, and producers are increasingly stepping up to prove their products are sound. The most common question about concentrates is the validity or safety of the solvents being used in the extraction process and the allowable limits for those solvents.
As producers begin to incorporate more stringent safety protocols into their operations, guidelines on recommended acceptable levels for residual solvents in Cannabis extracts will be a primary objective.
Solvents are broken into three classes
Class 1 solvents are recommended not to be employed in the manufacture of Cannabis extracts, excipients and drug products because of unacceptable levels of toxicity and their deleterious environmental effects. Common Class 1 solvents to be avoided include benzene. Class 1 solvents are only permitted when their use is unavoidable in order to produce a drug that can be justified in a risk-benefit trade-off. Class 1 solvents should never be used.
Class 2 solvents are not recommended for use outside a stringent Good Manufacturing Practice environment in which the solvents are tightly controlled and continuously monitored because of their dangerous effects. No Cannabis processors operating in Washington comply with these tight restrictions. One example of a common Class 2 solvent recommended for extracting Cannabis is hexane.
Hexanes are significant constituents of gasoline. They are colorless liquids at room temperature, with a gasoline-like odor. Hexanes are used in glues for shoes, leather products, cleansing and degreasing formulas, textile manufacturing, and the extraction of cooking oils from seeds.
However, long-term toxicity of hexane in humans is well known, and extensive peripheral nervous system failure is known to occur in humans chronically exposed to levels of hexane ranging from 400 to 600 parts per million, with occasional exposure up to 2,500 ppm.
Chronic intoxication from hexane and other Class 2 solvents have been observed in recreational solvent abusers and workers in manufacturing industries where exposure has occurred. Class 2 solvents should be limited or completely avoided in Cannabis products because of their inherent toxicity. Common Class 2 solvents in pharmaceutical products include hexane and methanol.
Class 3 solvents with a low toxic potential might be regarded as less toxic and of lower health risk. No Class 3 solvents are known to have a human health hazard at acceptable levels in Cannabis extracts. Safe common Class 3 solvents include ethanol. However, no long-term toxicity or carcinogenicity studies have been conducted for several of the Class 3 solvents.
Data from short-term studies suggest that Class 3 solvents pose little toxic risk. Acceptable levels for Class 3 solvents are generally stated at 50 milligrams per day or less (5,000 ppm or 0.5 percent).
Only Class 3 solvents should be used in solvent-based Cannabis extractions because of their low toxicity. However, it is crucial that Cannabis extracts be tested to ensure levels don’t exceed allowable limits. Isopropyl alcohol is a common solvent used in Cannabis extractions from the Class 3 solvent list.
However, this is one solvent with associated health risks, especially when allowable limits are exceeded. Isopropyl extractions should be approached with caution or completely avoided unless the safety of the product can be ensured.
Isopropyl alcohol and its metabolite, acetone, act as central nervous system depressants. Poisoning can occur from ingestion, inhalation or absorption and can result in headaches, dizziness, central nervous system depression, anesthesia, nausea, vomiting, coma or even death.
Presumably due to the low toxicity of residues, isopropyl alcohol is popular in pharmaceutical applications. However, levels of isopropyl alcohol generally far exceed acceptable limits with current applications of this solvent in the marijuana industry.
Another area of concern is the use of denatured alcohol or methylated spirits. Denatured alcohol has additives to make it undrinkable (poisonous, foul taste and smelly) in order to discourage recreational consumption. Because the alcohol has been denatured so as to be inconsumable, it only makes sense denatured alcohol should never be used in Cannabis extractions.
Just because a chemical is not listed in one of the solvent tables -- a list of several solvents and their effects -- it does not mean it is safe. Naphtha is a common solvent used in cannabinoid extractions. Naphtha is a mixture of hydrocarbons and is a component of natural gas condensate or distillation product from petroleum or coal tar. Common products made with naphtha include cleaning solvents, camp stove fuel and lighter fluid.
Naptha is not listed on the solvent tables and should not be used in Cannabis extractions. Like many hydrocarbon products, Naptha is a product of a refining process in which a complex soup of chemicals is broken into another range of chemicals. A range of distinct chemicals are in each product, which makes it difficult to compare and identify specific carcinogens.
Only Class 3 solvents should be used for extraction, and then only with tight controls in place. Some solvents and extraction methods not listed on the tables, and they might be safe. For example, butane and CO2 -- or cow milk butter, for that matter -- are not on the list, but are acceptable methods of extraction when safety protocols are met.
Purity or grade of these solvents can also be an issue because only high-purity or food-grade solvents should be used in cannabinoid extractions. Although ethanol is a Class 3 solvent, consumption of food grade ethanol above 50 milligrams per day is generally accepted in tincture-based products.
As with all therapeutic remedies, any adverse health effects or risk for abuse should be taken into consideration, and a doctor should be consulted if there are any concerns.
Analytical 360, a Seattle company that tests the quality of therapeutic cannabinoids, recommends patients verify test results before consuming concentrates derived from any solvent and nonsolvent-based Cannabis extracts before consumption.