This study evaluated the agronomic performance and safety of three medicinal Cannabis sativa L. cultivars grown under outdoor field conditions in Patagonia, Argentina, irrigated exclusively with treated municipal wastewater. Measured outputs included soil physicochemistry, irrigation-water quality, yield and cannabinoid profiles, and heavy-metal concentrations in dried flowers and derived medicinal oils. The heavy-metal findings are irrigation-context and plant-product data from a small field experiment (n=3 cultivars, one composite sample per cultivar per matrix), not a retail market survey.
Key numbers
All heavy-metal concentrations are reported in mg/kg (equivalent to µg/g or ppm) on a dry-weight basis for solid samples (soil, dried flowers) and in mg/L for liquid samples (water, medicinal oils). The limit of quantification (LOQ) is 0.20 mg/kg for solid samples and 0.002 mg/L for liquid samples (Table 5 footnote, p. 10). Values designated “<Loq” indicate below-LOQ measurements; the LOQ for solids (0.20 mg/kg = 200 µg/kg) was set by the analytical method.
Irrigation water (reclaimed wastewater)
All heavy-metal concentrations in irrigation water were below the LOQ of 0.002 mg/L (2 µg/L), with the exception of copper and zinc, which were detected at very low levels (copper: 0.035 ± 0.001 mg/L; zinc: 0.116 ± 0.01 mg/L) (Results, p. 6, Water quality section).
Soil (0-10 cm layer, three sampling times over 91 days; Table 3, p. 6)
The authors state that soil heavy-metal concentrations remained stable throughout the cultivation period, with only minor fluctuations (p. 6). All soil values were between one and two orders of magnitude below Argentine thresholds for agricultural soils under Regulatory Decree 831/93 of National Law 24,051 (p. 10).
Dried flowers (Table 5, p. 10; dry-weight basis; mg/kg)
The paper reports a cross-cultivar mean lead concentration for dried flowers of 0.88 mg/kg (880 µg/kg), with the highest values in Pachamama and the lowest in Conicet (p. 8). The text states this exceeds the maximum allowable limit established by California regulations; the California Department of Cannabis Control edible limit for lead is 0.5 mg/kg and the inhalable limit is 0.012 mg/kg (Table 5 notes and Discussion, p. 8-10). Arsenic and cadmium were below the LOQ (0.20 mg/kg) in all three cultivars. Cobalt was below the LOQ in Conicet but detectable in Mariquita (0.42 mg/kg) and Pachamama (0.34 mg/kg). Chromium was below the LOQ in Conicet but detectable in Mariquita (0.66 mg/kg) and Pachamama (0.53 mg/kg). Nickel was below the LOQ in all three cultivars.
Note on lead values in Table 5: The table (p. 10) lists 5.8 mg/kg for Conicet and 5.5 mg/kg for Mariquita and Pachamama in dried flowers, while the text at p. 8 states an average of 0.88 mg/kg with highest values in Pachamama and lowest in Conicet. The text narrative and Table 5 are internally inconsistent. The mean of 0.88 mg/kg stated in the narrative is used in the Discussion for regulatory comparison. This discrepancy should be verified against the original published table before any regulatory or synthesis use.
Medicinal oils (Table 5, p. 10; mg/L basis for liquid samples)
In medicinal oils, arsenic, cadmium, cobalt, chromium, nickel, and lead were all below the LOQ of 0.002 mg/L. Only copper (mean 0.54 mg/L across cultivars) and zinc (mean 1.80 mg/L across cultivars) were detected. The highest copper concentration was in Mariquita oil; Conicet oil showed the highest zinc levels (p. 8).
Methods (brief)
Three Cannabis sativa L. cultivars registered at the Argentine National Seed Institute (INASE): Conicet (Type I, THC-dominant), Mariquita (Type II, CBD-THC balanced), and Pachamama (Type III, CBD-dominant). Plants grown from clonal propagation, transplanted outdoors in Puerto Madryn, Chubut, Argentina (42 degrees 47’ 10.4” S, 65 degrees 00’ 28.2” W; cold arid steppe climate, BSk) on a sandy-loam soil. Irrigated exclusively with municipal treated wastewater via automatic drip system at 5 L per plant per day throughout the cultivation period (December 2021 to March 2022; 78-90 day crop cycle). No potable-water control treatment was included. Sample preparation and analytical methods for heavy metals followed standard methods described in the American Public Health Association (APHA 2017) for water and U.S. Salinity Laboratory Staff methods for soils. Analysis by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). LOQ: 0.20 mg/kg for solid samples, 0.002 mg/L for liquid samples. CRM and recovery data are not reported in the paper.
Evidence fitness
This study provides plant-product heavy-metal data for dried Cannabis sativa inflorescences and derived medicinal oils grown under outdoor conditions with reclaimed wastewater irrigation in Patagonia, Argentina. The data are relevant as agronomic and irrigation-context evidence for understanding heavy-metal transfer pathways from water and soil into cannabis plant products. The oil data are relevant as broad product context for cannabis oil products.
The data do not support market occurrence estimates: n=3 cultivars, one composite sample per cultivar per matrix, single growing season, single geographic site, non-retail products. The analytical method is ICP-AES rather than ICP-MS; the LOQ for solid samples (0.20 mg/kg = 200,000 µg/kg) is substantially higher than state cannabis action limits for lead (California edible: 0.5 mg/kg; California inhalable: 0.012 mg/kg) and cadmium (California inhalable: 0.02 mg/kg), so below-LOQ results for arsenic and cadmium cannot confirm compliance with state programs. Total arsenic only; inorganic arsenic speciation not measured. Total chromium only; hexavalent chromium not measured. No CRM or spike recovery data reported.
The paper focuses on feasibility of reclaimed-water irrigation for cannabis cultivation, not on contaminant surveillance. The heavy-metal discussion is a secondary outcome supporting the conclusion that treatment-system quality and monitoring are essential for product safety under reclaimed-water irrigation scenarios.
Limitations
Small sample size (n=3 cultivars, one composite sample per cultivar per matrix); results represent single growing season at one site in Patagonia, Argentina, not a population-representative sample. LOQ of 0.20 mg/kg for solids precludes reliable quantification at state cannabis action limits for lead (California inhalable: 0.012 mg/kg) and cadmium (California inhalable: 0.02 mg/kg). No CRM, blank, duplicate, or spike recovery data reported. The apparent inconsistency between the Table 5 lead values and the p. 8 narrative average (0.88 mg/kg) requires verification. ICP-AES method has higher detection limits than ICP-MS used in most regulatory cannabis surveys. Geographic scope limited to Patagonia, Argentina; Argentine reclaimed-water irrigation conditions differ from regulated North American or European cannabis markets.
Related evidence
- Topicals (creams, balms, salves)
- Tinctures and sublingual oils
- Cannabis flower / dried herb
- Lead
- Cadmium
- Arsenic
- Chromium
- Nickel
- Copper
- Zinc
- Cobalt
Update history
The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git.
| Commit | Date | Change | Description |
|---|---|---|---|
| 437eae1613 | 2026-11-08 | major | 10 sections added; narrative text revised |