About 1 in 4 Cannabis Home Growers Used Chemical Additives, With Rates Declining Over Time
A survey of over 11,000 cannabis growers across 18 countries found 26% used chemical fertilizers or pesticides, with use declining compared to a decade earlier.
Quick Facts
What This Study Found
In the 2020-21 survey, 26% of cannabis growers reported using chemicals. The highest odds of chemical use were among male, older, urban growers who grew under artificial light to sell cannabis. In three countries tracked over time (Australia, Denmark, UK), chemical fertilizer use decreased significantly between 2012-13 and 2020-21.
Key Numbers
11,479 growers surveyed across 18 countries. 26% reported chemical use. Growers using soil and artificial light comprised over half of all chemical users. Significant reductions in chemical fertilizer use were observed between the 2012-13 and 2020-21 surveys in Australia, Denmark, and the UK.
How They Did This
Web-based convenience survey of 11,479 mainly small-scale cannabis growers from 18 countries (2020-2021). Logistic regression identified predictors of chemical use. Results were compared with data from a similar 2012-13 survey in three countries.
Why This Research Matters
Unregulated chemical use in cannabis growing poses health risks to consumers, especially since some plant growth regulators banned from food crops for decades have been found in cannabis fertilizer products. Understanding who uses these chemicals and why can inform harm reduction efforts.
The Bigger Picture
As cannabis legalization spreads, regulating the products used to grow it becomes increasingly important. This study highlights that the legal cannabis fertilizer market itself needs stricter oversight to protect both growers and consumers.
What This Study Doesn't Tell Us
Convenience (non-random) web sample may not represent all cannabis growers. Self-reported chemical use may be underreported. The two survey waves used different samples, limiting direct comparison.
Questions This Raises
- ?What specific chemicals are most commonly used, and at what concentrations?
- ?How do residue levels in harvested cannabis compare between chemical-using and non-chemical growers?
Trust & Context
- Key Stat:
- 26% of growers used chemicals, with soil + artificial light growers making up over half of chemical users
- Evidence Grade:
- Moderate: large international sample with statistical modeling, though limited by convenience sampling and self-report.
- Study Age:
- 2025 study using 2020-2021 survey data.
- Original Title:
- Growing practices and the use of potentially harmful chemical additives from a web survey of mainly small-scale cannabis growers in 18 countries.
- Published In:
- The International journal on drug policy, 144(Pt 3), 104662 (2025)
- Authors:
- Lenton, Simon(4), Potter, Gary, Fortin, Davide(4), Granville, Ashely, Grigg, Jodie, Sevigny, Eric, Wilkins, Chris, Decorte, Tom, Barratt, Monica
- Database ID:
- RTHC-06922
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
What kind of chemicals were growers using?
Chemical fertilizers, pesticides, and plant growth regulators (PGRs), some of which have been banned from food crops for decades but appear in products marketed to cannabis growers.
Which growers were most likely to use chemicals?
Male, older, urban growers who grew under artificial light, used soil or non-soil media, grew to sell, and believed cannabis was legal in their area.
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Cite This Study
https://rethinkthc.com/research/RTHC-06922APA
Lenton, Simon; Potter, Gary; Fortin, Davide; Granville, Ashely; Grigg, Jodie; Sevigny, Eric; Wilkins, Chris; Decorte, Tom; Barratt, Monica. (2025). Growing practices and the use of potentially harmful chemical additives from a web survey of mainly small-scale cannabis growers in 18 countries.. The International journal on drug policy, 144(Pt 3), 104662. https://doi.org/10.1016/j.drugpo.2024.104662
MLA
Lenton, Simon, et al. "Growing practices and the use of potentially harmful chemical additives from a web survey of mainly small-scale cannabis growers in 18 countries.." The International journal on drug policy, 2025. https://doi.org/10.1016/j.drugpo.2024.104662
RethinkTHC
RethinkTHC Research Database. "Growing practices and the use of potentially harmful chemica..." RTHC-06922. Retrieved from https://rethinkthc.com/research/lenton-2025-growing-practices-and-the
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.