For years those growing non-Hemp CBD, typically marijuana or drug Cannabis >0.3% THC, have said it was less likely to uptake heavy metals and other toxins than Hemp. It was a silly assertion, of course, as Cannabis is Cannabis. Ironically, because of this canard Hemp might actually be “cleaner” than marijuana, as it may be tested more due to its phytoremediation potential. This study lays it bare:
A narrative review on environmental impacts
of cannabis cultivation
Journal of Cannabis Research, volume 3, Article number: 35 (2021)
[…]
Phytoremediation potential
Cannabis has gradually garnered attention as a “bioremediation crop” because of its strong ability to absorbing and storing heavy metals (McPartland and McKernan 2017). It can remove heavy metal substances from substrate soils and keep these in its tissues by means of its bio-accumulative capacity (Dryburgh et al. 2018). Usually, it takes up high levels of heavy metals from the soil or growing medium via its roots and potentially deposits into its flowers (Seltenrich 2019). Tainted fertilizer uptake from the soil is often a source of heavy metals contamination such as arsenic, cadmium, lead, and mercury. Singani and Ahmadi reported that Cannabis sativa could absorb lead and cadmium from soils amended with contaminated cow and poultry manures (Singani and Ahmadi 2012). Though limited studies discussed the effectiveness of cannabis for heavy metals removal, many studies have addressed the uptake of heavy metals by industrial hemp (Campbell et al. 2002; Linger et al. 2002). It indicates that the cannabis plant is qualified as a phytoremediation of contaminated soils. […]
Here are the studies cited, in order:
Contaminants of Concern in Cannabis: Microbes, Heavy Metals and Pesticides
Cannabis contaminants: sources, distribution, human toxicity and pharmacologic effects
Cannabis Contaminants: Regulating Solvents, Microbes, and Metals in Legal Weed
Remediation of Benzo[a]pyrene and Chrysene-Contaminated Soil with Industrial Hemp (Cannabis sativa)