Remediating Contaminated Hemp Crops

Hemp is a renowned hyperaccumulator, and is good at what it does – perhaps, even too good.

In 3 primary steps: phytoaccumulation, phytovolatilization, and phytodegradation, the renowned “king of crops” cleans up its environment via its roots, without falling victim to the contaminants itself.

However, in a highly toxic environment and under unsuitable conditions, the case is somewhat different, and as a result, human health and crop safety may be at the brink of peril.

THE CONTAMINANTS’ CHECKLISTS

In 2008, farmer Vicenzo Fornaro went from 600 to 0 sheep in a single day due to the toxic dioxin spewing from a nearby steel mill.

Fornaro, who had bred livestock for ricotta and meat, had his entire herd culled when the Italian government discovered the toxic chemical in his sheep. This event significantly changed his life.

The one-time sheep farmer now had zero livestock. However, since he was not losing his land, he came up with a crazy idea: use hemp to leach out the chemicals from the soil – and it worked! He is not the first, though.

Following the nuclear disaster in Chernobyl, hemp proved to be one of the best phyto-remediating plants for soil clean-up and has since then been applied for similar purposes.

Paradoxically, this highly-praised power of the hemp plant is accompanied by it’s not so exceptional vulnerability to pathogenic attacks and accretion of absorbed toxins, contrary to former beliefs.

Unfortunately, the numerous safety blind spots and lack of regulatory oversights in the hemp industry are not helping. As a result, the sensitive and unsettling situation of crop contamination within the hemp sector is on the rise.

A SLICE FOR EVERYONE

Unlike other forms of agriculture, the industry has relatively insufficient knowledge on safety standards for agrochemicals in hemp cultivation and crop management.

This situation has caused several growers to make difficult decisions regarding potentially harmful chemicals in hemp plants without the benefit of data typically needed to inform pesticide policies.

At the 2019 State FIFRA Issues Research and Evaluation Group (SFIREG) in Arlington, Virginia, Liza, Fleeson Trossbach, a Virginia pesticide regulator, said: “We’re in a situation where production is already happening.” EPA officials also admitted to scrambling to take initial steps in making pesticides legal and safe to use on hemp crops.

However, the bioaccumulation predicament is not just a farmer’s problem. The effect of the limited data on what pesticide residue levels are safe for hemp products, particularly those intended for human consumption, runs through the supply chain, all the way down to the final consumer.

TAKING PREVENTIVE MEASURES

Now, while individual states and relevant federal organizations have begun formulating compliance standards for safety in industrial hemp farming, it remains a work in progress, with most of these developments creating even more confusion for farmers.

Therefore, until farmers get the solutions they need from the higher powers, it is up to them to maintain and ensure the safety of their crops for their sake and the consumers’.

Below is a list of stages at which testing should be conducted to effectively and efficiently keep track of, and maintain, crop safety:

FIRST TESTING PHASE: PRE-PLANTING/MEDIUM ANALYSIS

WHAT TO CHECK FOR: HEAVY METALS & CHEMICAL ELEMENTS

Every true hemp grower, even traditional crop farmers, will attest to the importance of medium testing before planting.

This form of testing enables timely and effective resolution of field issues through the in-depth analytical review of the medium and its constituents; contaminants included.

Thus, the significance of soil testing should never be undermined, as a highly contaminated medium will render inadequate any hemp biomass grown for therapeutic or food purposes.

SECOND TESTING PHASE: POST-HARVEST

WHAT TO CHECK FOR: CONTAMINANTS & CANNABINOIDS

According to industry experts, plants with moisture levels above 12% run a higher risk of microbial and insect infestation. Moreover, high humidity levels are never great for long-term storage.

It is, therefore, crucial to test hemp harvests and storage environments for moisture levels to eliminate a prime contamination risk. Similarly, residual pesticides and other agrochemicals should be scanned for at this stage.

CORRECTING CONTAMINANTS

Taking preventive measures is widely considered the best bet to keep hemp yields contaminant-free, but there is an hitch. These contaminants are ubiquitous, and hemp is ever ready to take them up, making the quest of attaining total purity difficult. Thus, decontamination at every possible stage is a necessity.

In selecting what decontamination solution to employ, the following factors are to be considered:

1. The nature of the contaminant.
   
2. The crop variety.
   
3. The purpose for cultivation.

Unfortunately, studies have shown that it remains almost impossible to recover crops from heavy metal contamination in the field. Nevertheless, with microbial-contaminated crops, there are some exciting remediating innovations to utilize:

Gamma Irradiation

In most countries with a national medicinal cannabis program, there is a list of strict guiding regulations on herbal cannabis production, and gamma irradiation seems to check off most of the stipulated criteria.

This procedure involves exposing the target material to high-energy photons, with levels elevated enough to destroy the DNA or RNA of the contaminating microorganism.

However, while this method is widely accepted and even endorsed by the World Health Organization, the topic of irradiation as a decontamination technique remains a somewhat controversial one, sparking a plethora of intense debates amongst the general public.

Meanwhile, it has been successful for some Canadian hemp producers (and consumers). To meet microbial safety requirements, some of these producers that had initially pledged to stay off irradiation for decontamination have had to fall back to these solutions.

E-Beam (Beta) Irradiation

This form of irradiation is quite similar to gamma irradiation but differs in various aspects.

First, beta irradiation uses less energy than gamma while retaining a vast majority of the many benefits of gamma. Then, unlike most decontaminants, it leaves no residue after sterilization, and since it does not require extreme heat, it is less likely to damage desired compounds.

On the other hand, it’s elevated energy levels might cause the rearrangement of inherent molecules in the plant material, thereby forming new molecules.

Nevertheless, beta-irradiation is proven to have little to no detrimental effect on the overall quality of plant material as it does not require a radioactive source like gamma. Instead, it uses an electron accelerator, making it safe and healthy for human consumption and the environment.

Furthermore, certain microorganisms like Penicillium expansum have shown more sensitivity to E-beam than gamma irradiation.

Cold Plasma Treatments

This method, on the other hand, uses an entirely different system for disinfection and sterilization.

With the cold plasma technique, ions, electrons, photons, and free radicals in gases are discharged at atmospheric or sub-atmospheric pressure. When applied in decontamination, these levels prompt oxidative reactions, which results in the apoptosis and subsequent death of the microorganisms.

Comparing this technique to the fore-listed, its less penetrative activity (surface action) makes it more desirable for sterilizing crops as it does not alter, in any depreciable way, the concentration of the cannabinoids and terpene molecules.

Plus, it is more affordable and is relatively easier to implement in on-site treatments.

CONCLUSION

Thanks to modern technology and innovations, the underlying problem of effectively dealing with crop contaminants has met its match.

Again, not all of the available solutions are as practical as they should be. In tandem with the farmer’s chosen solution, it is necessary to follow good manufacturing practices.

Nevertheless, it is welcome for the industry to have workable solutions that help indicate we are on the right track to pushing the industry to a comfortable and gratifying height.