In brief The US hemp industry is growing thanks to a surge in demand for cannabidiol (CBD) in products such as cosmetics, dietary supplements, and food. Many states have programs governing hemp cultivation, but federal regulators are struggling to streamline the rules. Hemp producers and processors are unhappy with the US Department of Agriculture’s first attempt to develop uniform national standards for growing hemp. They are also worried about the Food and Drug Administration’s wavering position on CBD in dietary supplements and food, which is creating uncertainty for end markets for hemp.

Regulating hemp and the products derived from it, such as cannabidiol (CBD), should be relatively straightforward. The primary objective is to limit the amount of one specific, well-known chemical: ∆9-tetrahydrocannabinol (∆9-THC), the main psychoactive component of cannabis. But as US federal regulators are finding, little is simple when it comes to producing and processing natural products.

Many US states have been overseeing hemp production in their jurisdictions since 2014, when Congress authorized states to conduct hemp pilot programs. In 2018, Congress removed hemp—defined as cannabis containing no more than 0.3% of ∆9-THC on a dry-weight basis—from the Controlled Substances Act. Lawmakers intended the move to pave the way for the US hemp industry to take off.

To bring order to the patchwork of state rules, the 2018 farm bill also directed the US Department of Agriculture to develop federal standards for hemp production. The USDA released the first federal rule in October 2019. The agency plans to update the rule at some point before it expires in October 2021. But first, the USDA wants to gain experience implementing the rule and receive input from various stakeholders.

So far, those stakeholders are very unhappy. Of the thousands of comments submitted to the USDA on the interim rule, the majority claim that the rule is unworkable. Concerns from hemp farmers have prompted lawmakers representing Indiana, Oregon, and Virginia, as well as various state agriculture departments and farm bureaus, to write letters to the USDA. Several states, including Arkansas, Maine, Minnesota, Missouri, New Mexico, and Wisconsin, have opted to continue operating under their state plans until those expire in October 2020. Other states are likely to follow suit.

The concerns center on the THC limit and how to handle “hot” hemp, which is hemp with too much THC. These issues, plus uncertainty related to federal regulation of CBD in food and dietary supplements, threaten to hamstring an industry that is just getting off the ground.

0.3% THC

One of the biggest issues that hemp growers face is controlling the level of THC in their crops so that they have no more than 0.3% at 15 days before harvest, the window of time specified in the USDA rule. Although a few companies claim their seeds will produce hemp that has more than 10% CBD while keeping to this THC limit, most growers and researchers argue that it will be nearly impossible to grow plants to full maturity and comply with the USDA’s policy.

Regulatory red tape These are the top concerns raised by the US hemp industry about the US Department of Agriculture interim rule. • The tetrahydrocannabinol (THC) limit includes psychoactive ∆9-THC as well as tetrahydrocannabinolic acid, which is not intoxicating. • The THC limit is difficult to meet under all growing conditions. • Whole plants should be tested, not just flowers. • Fifteen days between testing and harvesting is insufficient. • The scarcity of Drug Enforcement Administration–registered labs will create testing bottlenecks. • A remediation pathway is needed for crops that test above the THC limit. • Uncertainty related to cannabidiol in food and dietary supplements is limiting markets for hemp.

Many factors affect THC levels in hemp, including nutrients in the soil, weather, plant spacing, and other growing conditions. Seeds planted in one region produce a different chemical profile than the same seeds planted elsewhere. Most farmers plant hemp to produce high amounts of CBD for use in food, dietary supplements, cosmetics, and other products. To make the plants profitable, growers typically aim for a minimum of 10% CBD. As hemp plants mature, CBD levels rise, but so do THC levels.

The reason lies in how plants make CBD and THC. The two compounds arise from the same biosynthetic pathway up to cannabigerolic acid. Enzymes then convert cannabigerolic acid to cannabidiolic acid (CBDA) and tetrahydrocannabinolic acid (THCA). CBDA and THCA then decarboxylate to yield CBD and ∆9-THC. Because the compounds have the same cannabigerolic acid precursor, increasing one typically means increasing the other.

Another point of contention is whether the 0.3% limit should apply to just ∆9-THC or to total THC, which is ∆9-THC plus THCA. Congress specified ∆9-THC in the Agriculture Improvement Act of 2018 (the 2018 farm bill). But the USDA focuses on total THC to prevent people from growing varieties of hemp that are high in THCA levels but low in ∆9-THC. When heated, THCA decarboxylates to ∆9-THC, the psychoactive component in cannabis. Some states currently require only ∆9-THC testing for hemp, while others require total THC testing. Those in favor of setting the federal limit only for ∆9-THC argue that the farm bill definition of hemp is based on ∆9-THC, not total THC.

Because of the desire for high CBD and the USDA’s defining the THC limit as total THC, experts predict that under the interim rule, as much as 40% of the hemp grown in the US will test above the 0.3% total THC threshold. To make it more likely that plants will not exceed that threshold, the hemp industry is encouraging the USDA to make several changes to its policy related to testing THC.

Many in the industry advocate raising the THC threshold to 0.5 or 1%, especially if it stays as total THC. The 0.3% limit for hemp is arbitrary and not based on science. Researchers have shown that hemp containing 1% total THC does not produce intoxicating effects, particularly when it contains high CBD levels (Psychopharmacology 1988, DOI: 10.1007/bf00176846). Many marijuana varieties sold in states where it is legal contain at least 15% total THC. Concentrated cannabis products, such as extracts, contain 50–90% THC.

In addition, the USDA does not have sufficient data yet to determine how agricultural variability affects THC levels in hemp. “Let’s go farm it in 50 states” to get the data, says Jeffrey Raber, CEO and cofounder of the Werc Shop, a cannabis contract manufacturing and testing firm. Then the USDA could evaluate all the samples over a 2-year period and determine what percentage of crops would fail for a given THC limit. “If we defined the THC limit at, say, 0.75%, maybe we would have only failed 2% of crops,” he suggests.

Many growers also want the USDA to allow testing of the entire plant, including the stems, leaves, and flowers. The USDA requires sampling of just the flowers, which contain the highest levels of THC and CBD. But typically the entire plant is used industrially, even for CBD extraction.

I have not seen any data from our work or from our growers that would suggest you can consistently get close to 10% CBD without going over 0.3% total THC. Keith Edmisten, professor, North Carolina State University

Researchers at North Carolina State University are collecting data on THC and CBD levels in different varieties of hemp grown outdoors under various conditions. So far, the data suggest that no common varieties will meet the USDA’s requirements. “I have not seen any data from our work or from our growers that would suggest you can consistently get close to 10% CBD without going over 0.3% total THC,” says Keith Edmisten, an NC State professor of crop and soil sciences and a cotton and hemp specialist.

In addition, “the closer you get to harvest, the higher the THC is going to go,” Edmisten says. At full maturity, hemp plants grown for CBD often contain 0.8% total THC or more. Many hemp growers and state agriculture departments are urging the USDA to extend the 15-day harvest window to 30 days or more. If plants are tested 30 days before harvest, they are much less likely to exceed 0.3% THC than if they are tested 15 days before harvest.

The longer window would also give growers more time to harvest their plants. “Two weeks is not enough time to sample the crop,” Edmisten says. “We know from our experience, you would have to hire a lot more people.”

Creating cannabinoids Cannabidiol (CBD) and Δ9-tetrahydrocannabinol (Δ9-THC) share the same biosynthetic pathway up to cannabigerolic acid. Increasing CBD levels in hemp plants therefore typically increases THC levels.

Handling “hot” hemp

Another major concern is that the USDA’s policy allows only laboratories registered with the US Drug Enforcement Administration to test hemp plants. If test results show that a hemp plant contains greater than 0.3% THC, the DEA considers the plant to be a controlled substance. Under federal law, only DEA-registered labs are allowed to handle controlled substances.

The 15-day testing window plus the restriction to DEA-registered labs “will create a tremendous backlog in terms of testing,” says Jonathan Miller, general counsel of the US Hemp Roundtable, a consortium of hemp and CBD companies and organizations.

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The USDA has identified 37 DEA-registered labs in the US. Some states have more than others. Although many states have several labs certified to test medical marijuana in their jurisdictions, the USDA’s policy prohibits those labs from testing hemp because they are not registered with the DEA.

At a minimum, the USDA should remove the DEA lab registration requirement in states where cannabis is legal, officials at Confidence Analytics, a cannabis testing lab in Washington State, say in comments submitted to the USDA. Allowing state-certified labs that have extensive experience testing cannabis plant material to participate in the hemp program “will ensure that the analytical needs of the producers can be met in a timely manner and with quality, accurate results,” the Confidence Analytics officials say.

Excluding labs that are experienced in THC testing is “unfortunate,” the Werc Shop’s Raber says. But with marijuana still a controlled substance federally, it gets complicated to combine marijuana testing under state law and hemp testing under federal law in the same place, he says. If the DEA wants to inspect a lab or ensure that hot hemp is destroyed, what happens if marijuana is in the same facility? The only way to truly resolve the issue would be to make cannabis legal at the federal level, he notes.

Then there’s the issue of what to do with hemp crops that turn up hot. Under the USDA’s interim rule, any hemp crops that test above 0.3% THC need to be destroyed. If hemp plants have more than 0.5% THC, the grower is charged with negligence. Growers who are found negligent three times are prohibited from growing hemp for 5 years.

“We think there needs to be more lenient guidelines when it comes to what happens when the hemp tests hot,” Miller of the Hemp Roundtable says. “We don’t think that something that is 0.5% THC is necessarily caused by negligence. It could be caused by climate or soil.” A finding of negligence should mirror what negligence means in the law, not some arbitrary standard, he says.

Rather than destroy hot crops, the hemp industry is pushing for remediation of the plants. One option is to allow farmers to use hot hemp on their farms for fuel, feed, or other purposes. Another possibility is to follow the lead of states that allow farmers to send hot hemp plants to a state-licensed facility where the THC is removed and destroyed. In such cases, farmers may sell the salvaged material.

Many hemp farmers are advocating for a third alternative, in which hot hemp plants are processed in such a way that the final product does not contain more than 0.3% THC. It is much easier for the processor to control the THC level in a finished product, such as a cosmetic, tincture, or dietary supplement, than it is for the farmer to control the THC level in the plants, they say.

We think there needs to be more lenient guidelines when it comes to what happens when the hemp tests hot. Jonathan Miller, general counsel, US Hemp Roundtable

CBD uncertainty

The USDA’s rule addresses only hemp cultivation. It does not address the marketing and sale of products derived from hemp. The US Food and Drug Administration has regulatory authority over foods, dietary supplements, and cosmetics. But the FDA has been slow to adopt rules governing the sale of hemp-derived products that are under its jurisdiction. The agency said last year that it does not consider CBD generally recognized as safe, so it can’t be added to food without premarket approval from the FDA. CBD also does not meet the definition of a dietary supplement, the agency said.

The FDA is concerned about the potential for CBD to cause liver injury and possible interactions with pharmaceuticals. The agency is also warning consumers about reports of CBD products containing pesticides, heavy metals, and other contaminants.

Even so, the FDA is exercising enforcement discretion and not going after companies making food and supplements containing CBD, even when they are adulterated with contaminants. So far, the agency has sent warning letters only to CBD companies making egregious health claims.

“I think we would have seen a different course of action from the FDA if there was a true safety concern for the ingredient” at levels showing up in consumer products, says Tami Wahl, a Washington, DC–based attorney and lobbyist. “Fortunately, we are not dealing with a toxic substance,” at low doses.


“We’d like to see the FDA committed to testing” CBD products for contaminants, such as pesticides, mold, and heavy metals, before they enter the food chain, the Hemp Roundtable’s Miller says. Cannabis plants, including hemp, are notorious for their ability to accumulate heavy metals from soil. “Heavy-metal contamination doesn’t matter if you are using the hemp for construction purposes, but it really does matter if the hemp is being used for food or CBD,” Miller says.

Wahl is hopeful that Congress will intervene and pass legislation this year to resolve some of the regulatory uncertainty related to the FDA’s position on CBD. “A legislative solution is the most expedient way,” she says.

In January, Rep. Collin Peterson, chair of the Agriculture Committee in the House of Representatives, introduced a bill (H.R. 5587) that would give the FDA the flexibility to allow hemp-derived CBD in dietary supplements.

“The last two Farm Bills were landmark successes for hemp, but we are still very early in this process, and growers need regulatory certainty,” Peterson said in a statement when he introduced the bill. “This bill will allow FDA to regulate CBD that comes from hemp as a dietary supplement, providing a pathway forward for hemp-derived products.”

As for the USDA, the agency has no plans to change its interim rule for the 2020 or 2021 growing seasons. The rule sunsets in October 2021, at which time the agency is likely to replace it with a new rule that addresses some of the concerns.