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Multiple Case Studies Show Potential Danger of Cannabis Contaminants

By Alexander Beadle
Published: Jul 22, 2018   
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Many studies have been carried out to quantify the short and long-term health effects of cannabis use, and the general consensus within the medical community at present appears to be that for medicinal users, the benefits outweigh the small number of side effects. For recreational users, the inclusion of age restrictions in law leaves it up to the adult in question to make an informed decision about whether they deem those side effects tolerable.

In addition to the effects of the cannabis itself, it is also important to address the topic of cannabis contamination in discussions about cannabis safety. Most medicinal drugs are synthesized in laboratory conditions and are unlikely to experience much contamination from external sources if laboratory procedures are followed correctly. Other recreational drugs such as alcohol are distilled or filtered as part of their production process which decreases the likelihood of contamination. 

Contrastingly, the cultivation of cannabis is open to many possible avenues of contamination as it must be farmed, harvested and processed as opposed to being synthesized in a laboratory setting.

Microbial Contamination of Cannabis Plants

Improperly prepared cannabis can play host to microbial life that thrives in the humid farming conditions typically utilized to maximize plant growth. These microbial contaminants can go on to cause outbreaks of infection if present in high enough levels, as was the case in a 1981 outbreak of Salmonellosis. There it was discovered that the outbreak was caused by cannabis plants that were contaminated with Salmonella muenchen. Fungal spores are also a concern, and there have been reported cases of fungal spores related to the growth of Aspergillus fungi causing serious respiratory issues in immunocompromised people.

Given the medicinal applications of cannabis, this impact on immunocompromised patients is concerning. One simple approach to combatting contamination is ensuring that all harvesting, handling, and preparation of cannabis happens in a hygienic environment. In addition to preventative measures, gamma-irradiation has also been successfully trialed as a method for sterilizing contaminated cannabis products. 

Cancer Risk and Regular Cannabis Use

Rigorous testing of medicinal and recreational cannabis around the world has revealed the presence of numerous carcinogenic and suspected carcinogenic contaminants in cannabis samples, with many being linked to the use of pesticides. Despite this, the risk of respiratory tract or lung cancers does not seem to be affected by light or moderate smoking of cannabis.

Arsenic and aflatoxins can also be present in cannabis plants, predominantly due to contaminated soil or fungal infection. Both arsenic and aflatoxins are classified as Group 1 substances by the United Nations, which states that both are known carcinogens and as such should be avoided. 

Legislative measures are thought to be the best way to tackle these risks. Reform of what pesticides can be used on cannabis plants is already underway in some states. California have chosen to introduce a blanket ban on the use of any pesticide on cannabis plants that is not already approved for use on food or is exempt from residue tolerance requirements is exempt from registration requirements. It is hoped that this ban, and other similar measures, can limit the risk of exposure to dangerous pesticide residues for cannabis users.

Endocrine Disrupting Cannabis Contaminants

Endocrine disruptors are biologically active materials that can interfere with the human endocrine system and disrupt normal hormonal function. They can decrease fertility and increase the risk of developing some autoimmune diseases, as well as prostate and ovarian cancers. Organophosphate-based insecticides and heavy metals are both endocrine disruptors that can come into contact with cannabis plants during their cultivation. 

One potential way of dealing with the heavy metal contaminants is by boiling the cannabis plants during processing. This extracts some of the metal from the plant matter into the hot water. The treated cannabis plants can then be removed from the water, dried, and prepared as normal. Insecticides can be dealt with in much the same way as other pesticides, with more hygienic preparation methods and improved legislation.

Future Considerations

The fact that cannabis must be grown as a plant and cannot be synthesized within a sterile lab environment opens up a number of potential sources for contamination. A number of preventative steps are being taken to minimize the risk of contamination, and the creation of methods to treat contaminated cannabis plants is an active area of research. Further research into the quantification of contaminants such as microbial life, pesticides, and heavy metals in cannabis is required so that scientists and regulators are able to better understand the scope of the issue and, the best approaches to minimizing risk. 


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