Nowadays, the main source of cannabinoids worldwide is cannabis plants, but we forget that cannabis is a crop that undergoes regular management to improve its growth, development, and yield. Many users only get to see the pharmaceutical products, extracts, edibles, or final buds, but have you ever thought about the chemicals used for growing cannabis or to control its pests? And, since we know the main consumption of cannabis is through smoking, could it be transferred into the smoke?
Cannabis is a living organism susceptible to diseases, pests, and infections. Spider mites, thrips and aphids are the most frequent pests that cannabis growers must face. Although there is some regulation for the use of pesticides in countries where cannabis is legal, there is no standardized protocol for their utilization yet. Traces are allowed in the final buds, if the pesticide is considered safe or moderately hazardous by The World Health Organization, but this assumption is based on studies of pesticides for oral intake, whereas inhalation safety has not yet been clarified.
Pesticides are retained in the trichomes of cannabis plants. The trichomes are very specialized structures located on the leaves and flowers of the plant, which mainly contain cannabinoids and terpenes. The latter are hydrophobic compounds and ironically, pesticides too. Therefore, trichome density and retention of pesticides is correlated, meaning that the more the trichomes, the more the pesticides. Then, if cannabis is smoked, pesticides are transferred into the smoke through a process called pyrolysis. Pyrolysis is the chemical decomposition of organic materials through the application of heat, and it can turn some pesticides into a more toxic chemical that will end up being absorbed by the lungs of the consumer. For that reason, some growers have recently started to seek alternative pesticides, such as natural extracts like neem oil.
Neem oil meets the purpose of a regular pesticide, providing sufficient efficacy through its main active component called azadirachtin. Even though it appears to be a safe solution, there are case reports of neem oil poisoning with severe symptoms, but only through oral intake of high concentrations. Although neem oil toxicity through inhaling has never been explored, we cannot presume it is completely safe, but might be safer than synthetic pesticides.
There are some studies that had quantified pesticide residues in cannabis smoke from different smoking devices. They evidently outline the need of adequate regulatory guidelines with proper scientific studies that can give smokers confidence for consumption of cannabis. Even though we know that it is difficult to quantify the dose inhaled by each consumer, it should not represent any harm when smoked. Anyway, whether natural or synthetic, pesticides do not seem to have an immediate detrimental effect in humans when the pyrolysis fumes are smoked. Nevertheless, the long-term effect of chronic low-dose intake should not be underestimated.
Stay tuned – There is no greater ignorance than thinking you know it all.
- Sullivan, N., Elzinga, S., & Raber, J. C. (2013). Determination of pesticide residues in cannabis smoke. Journal of toxicology, 2013, 378168. https://doi.org/10.1155/2013/378168
- Antonious, F. G., & Snyder, C. J., (1993). Trichome density and pesticide retention and half‐life, Journal of Environmental Science and Health, Part B, 28:2, 205-219, DOI: 10.1080/03601239309372823 
- Mishra, A., & Dave, N. (2013). Neem oil poisoning: Case report of an adult with toxic encephalopathy. Indian journal of critical care medicine : peer-reviewed, official publication of Indian Society of Critical Care Medicine, 17(5), 321–322. https://doi.org/10.4103/0972-5229.120330 
- Taylor, A., & Birkett, J. W. (2020). Pesticides in cannabis: A review of analytical and toxicological considerations. Drug testing and analysis, 12(2), 180–190. https://doi.org/10.1002/dta.2747 
- Campos, E. V., de Oliveira, J. L., Pascoli, M., de Lima, R., & Fraceto, L. F. (2016). Neem Oil and Crop Protection: From Now to the Future. Frontiers in plant science, 7, 1494. https://doi.org/10.3389/fpls.2016.01494 
Masha Burelo  is a PhD Student at the University of Aberdeen. Her research explores Electrophysiology and behavioural evaluation in preclinical models of Alzheimer’s disease. Masha started her studies in veterinary medicine in Mexico and first became interested in cannabinoids when her dog developed epilepsy, then with close family members struck by Alzheimer’s Disease her interest in neuroscience, plants and the brain developed.