Abstract
Introduction:
Legal limits on the amount of cannabis sold per transaction in states with recreational cannabis may promote moderate use and limit diversion. However, state sales limits are heterogeneous, and difficult to interpret in terms of tetrahydrocannabinol dose equivalents.
Methods:
This cross-sectional study examined how transaction sales limits on recreational cannabis translate to tetrahydrocannabinol doses among U.S. states allowing commercial cannabis sales as of January 1, 2020. Weight-based quantity limits by cannabis type (flower/bud, concentrates, and edibles) were converted into grams of tetrahydrocannabinol content per transaction using known potency values in 2020.
Results:
Weight-based sales limits for flower and concentrate vary considerably across states (range=1.0–2.5 ounces for flower, 3.5–15.0 grams for concentrate) whereas limits for edible cannabis are heterogeneous. Four states have independent limits for each product category, and 6 states place limits across all products sold in the transaction. Because no states impose limits on the potency of flower or concentrates, the small differences in weight-based limits translate into large differences in grams of tetrahydrocannabinol allowed to be sold. Assuming a typical dose of 10 milligrams of tetrahydrocannabinol, current laws allow for sales of up to 560 (Alaska) to 2,283 (Michigan) doses per transaction based on median product potencies.
Conclusions:
All states allow a large number of tetrahydrocannabinol doses per transaction, larger than what is typically consumed by daily users over a month. States concerned about public health and diversion should consider reducing sales limits and basing them on total tetrahydrocannabinol content across all purchased products.
INTRODUCTION
State experimentation with legal adult-use cannabis markets is receiving considerable attention from governments both within the U.S. and abroad. Although scholars are assessing effects on cannabis consumption and harm,1,2 an aspect receiving little attention is sales limits. By capping the amount of cannabis purchased by an individual at one time, sales limits are intended to reduce diversion from the legal market and to influence norms around consumption and impairment. There are a range of ways to institute sales limits. Uruguay restricts purchases at pharmacies to no more than 10 grams per week and caps potency at 10%.3 Canada does not restrict purchases directly, but does so implicitly by restricting possession in public to 30 grams.4
In the U.S., sales limits are based on product weight, but the amount of the psychoactive ingredient tetrahydrocannabinol (THC) varies considerably both within and across products. Thus, to understand how effective state sales limits are at discouraging excessive consumption or diversion, one must have a sense of how these sales limits translate into standardized doses of THC. Published information on the potency of cannabis products was used to translate current sales limits in states with commercial sales of recreational cannabis into standardized doses of THC.
METHODS
A public health lawyer conducted legal research using LexisAdvance to extract information on quantity limits for sales of flower, edibles, and concentrates in 2020. Limits on flower and edibles were standardized into ounces, and limits on concentrates were standardized into grams. Limits on grams of THC sold within a product, most frequently edibles, or across the entire transaction were also collected.
Weight-based limits were translated into grams of THC by multiplying weight by potency values published by Davenport,5 who reported the minimum, maximum, median, and IQRs for flower and extracts included in Washington state’s seed-to-sale system as of October 2017 (Table 2). Potency ranges reported for high-THC flower in Davenport5 were used, as it represented 99% of the flower material sold in Washington that year. Similarly, Davenport’s5 values on high-THC cartridge extracts were used for assigning potencies for concentrates. After calculating product-specific grams of THC under various assumed potencies, total grams of THC were summed across products; this value was replaced by the total transaction quantity or THC sales limit when such limits existed and were lower than the sum of product-specific limits.
Finally, the total number of doses per transaction were calculated, as implied by these estimates. Although recent research suggests 5 milligrams of THC as a “standardized dose” for researchers studying cannabis,6,7 10 milligrams of THC was used as several state statutes utilize this standard for edible product labeling. This suggests 10 milligrams is more consistent with market behavior. To obtain the number of THC doses, the total weight-based grams of THC limits on flower and extracts were multiplied by 100 (1,000/10 milligrams) and then added to edible dosing limits based on 10 milligrams doses. The IRB at Boston University Medical Campus determined this to not be human subject research.
RESULTS
As of January 1, 2020, a total of 11 states and the District of Columbia had laws allowing adult use of cannabis and 10 states allowed commercial sales. Of these, the majority set product weight-based limits on the maximum amount of flower and concentrates that can be purchased, ranging from 1.0 ounce to 2.5 ounces for flower and 3.5 grams to 15.0 grams for concentrates (Table 1). Two states (Oregon and Washington) place product weight and volume limits on edibles, and 4 states (Colorado, Illinois, Massachusetts, and Nevada) place limits on the total grams of THC sold through edibles. Six states impose total transaction limits in addition to product-specific limits, but only Alaska explicitly limits the total amount of THC that can be sold per transaction (5.6 grams).
Table 1.
Legal Limits Imposed on Sales of Cannabis Products Sold for Recreational Use in U.S. States, as of January 2020
State | Sales limits on weight or volume on individual products | |||||
---|---|---|---|---|---|---|
Flower/Bud (ounces) | Concentrates (grams) | Solid form, edibles (ounces) | Edibles Liquid orm, drinks (fl oz) | Edibles (grams THC) | Product limits are interdependent | |
Alaska | 1 | 7 | NL | NL | NL | Yesc |
California | 1 | 8 | NL | NL | NL | Yesd |
Colorado | 1 | 8 | NL | NL | 0.8 | Yese |
Illinois | 1 | 5 | NL | NL | 0.5 | No |
Maine | 2.5 | 5 | NL | NL | NL | Yesf |
Massachusetts | 1 | 5a | NL | NL | 0.5 | Yese |
Michigan | 2.5 | 15 | NL | NL | NL | Yesf |
Nevada | 1 | 3.5b | NL | NL | 3.5 | No |
Oregon | 1 | 5 | 16 | 72 | NL | No |
Washington | 1 | 7 | 16 | 72 | NL | No |
Notes: As of January 1, 2020, Illinois’ emergency regulations had not yet addressed sales limits, so possession limits are assumed sales limits. In Maine, stores are not yet open.
Retailers cannot sell more than 5 grams of THC in marijuana concentrate, which matches possession limits for concentrate.
Retailers cannot sell more than one-eighth ounce (3,544 milligram) of marijuana concentrate which must not contain more than 3,500 milligrams of THC.
The combination of all products and product types (flower, concentrates, edibles) may not contain more than 5.6 grams of THC.
Concentrate contained in edibles are included in the concentrate sales limit, but flower sales limit is independent.
The limit on each of the 3 categories (flower, concentrate, edibles) is equivalent to one another, and therefore selling a percentage of the limit for 1 category reduces by the same percentage the limit on each of the other 2 categories.
The combination of flower and concentrates cannot exceed the flower limit, and the concentrate limit must also be observed. Concentrate contained in edibles are included in the concentrate sales limit.
NL, no limit specified; THC, tetrahydrocannabinol.
Considering the wide range in THC potency for flower (8%–34%) and concentrates (40%–97%), the total grams of THC per transaction allowed by these limits varies from <3 grams to approximately 33 grams of THC (Table 2). At minimum product potencies, the grams of THC sold in a transaction range from 2.3 (Massachusetts) to 10.5 (Michigan). At maximum product potencies for flower (34%) and concentrates (97%), grams of THC range from 5.6 (Alaska) to 33.6 (Michigan).
Table 2.
Translation of Weight-Based Quantity Limits Into Grams of THC for Cannabis Flower and Concentrate Products
Grams of THC per transaction assuming… | |||||
---|---|---|---|---|---|
State | Minimum potency per product | 25th percentile potency per product | Median product potencies | 75th percentile potency per product | Maximum potency per product |
Alaska | 5.07 | 5.60 | 5.60 | 5.60 | 5.60 |
California | 5.47 | 10.83 | 11.87 | 13.36 | 17.40 |
Colorado | 3.20 | 5.44 | 5.95 | 6.80 | 9.64 |
Illinois | 4.27 | 8.79 | 9.65 | 10.90 | 14.49 |
Maine | 7.27 | 15.92 | 17.53 | 19.91 | 27.25 |
Massachusetts | 2.27 | 5.39 | 5.95 | 6.80 | 9.64 |
Michigan | 10.47 | 20.82 | 22.83 | 25.71 | 33.55 |
Nevada | 3.67 | 7.77 | 8.54 | 9.67 | 13.03 |
Oregon | 4.27 | 8.79 | 9.65 | 10.90 | 14.49 |
Washington | 5.07 | 10.15 | 11.13 | 12.54 | 16.43 |
Assumed potency flower | 8% | 19% | 21% | 24% | 34% |
Assumed potency vaping | 40% | 68% | 74% | 82% | 97% |
Notes: Potency levels (minimum, maximum, 25th, 50th and 75th percentile) for flower and high THC cartridge extracts (for vaping) products from Davenport (2019). Edibles are excluded in these calculations. Stores are not yet open in Maine. For Alaska, Colorado, Maine, Massachusetts, and Michigan, where product limits are interdependent, the authors identified the product or combination of products generating maximum grams of THC.
THC, tetrahydrocannabinol.
Figure 1 shows final estimates of standardized 10 mg doses given different potency scenarios. The range of standardized doses varies from 226 doses at the lowest potency products (Massachusetts) to 1,046 (Michigan). At median product potency levels, all states enable purchases exceeding 500 doses, with 6 states exceeding 1,000 doses and 1 state exceeding 2,000 doses. Alaska, which limits total transaction amounts of THC, is capped at 560 doses regardless of potency. For transactions involving maximum potency products, purchases exceeding 1,450 doses were possible in the majority of states.
Figure 1.
Implied ranges of 10 milligram THC doses associated with state sales limits. Notes: The shaded portion of the bars represents the number of doses based on the IQR of product potencies, with the vertical line representing doses at median potency. The ends of the lines represent doses at minimum or maximum product potencies, respectively. Stores not yet open in Maine. Estimates do not incorporate edibles in Oregon and Washington, since edible limits in these states are based on product weight without specified limits on either the potency of product or the total amount of THC that may be sold in the form of edibles.
THC, tetrahydrocannabinol.
DISCUSSION
Placing limits on cannabis sales might appear consistent with public health goals of reducing excessive consumption and preventing diversion since the weight-based quantities limit the physical availability of cannabis. However, cannabis’s main intoxicating and psychoactive ingredient, THC, varies widely within and across products.5–7 Even when median product potencies are applied to the statutory limits, all states allow for >500 THC-standardized doses to be sold in a single transaction.
These limits are large relative to typical market purchase behavior. Information from household surveys8,9 and dispensary visitors10 suggest that typical purchase amounts from populations represented in these surveys tend to be small (<5 grams on average). Even daily users, who account for the majority of sales8,11,12 and report consuming approximately 1.6 grams of flower per day (i.e., 1.7 ounces per month),12,13 could purchase 2 weeks’ worth of cannabis in a single transaction in any state if they purchased up to the limit, and even more than a 2 week supply if they only purchased high-potency products.
Limits placed on the total transaction amounts or weights are more effective at reducing number of standardized doses sold than having only product-specific limits. For example, Massachusetts has the same product-specific weight limits as Illinois, but by imposing an equivalency limit on the entire transaction, Massachusetts allows considerably fewer grams of THC per sale than Illinois (5.95 grams vs 9.65 grams for medium potency products).
CONCLUSIONS
For those interested in purchasing large amounts of THC, basing transaction limits on product weight alone creates opportunities for overconsumption simply by purchasing products with increased potency. Accordingly, even if lower weight limits were applied, those wanting more THC could simply shift their purchases to higher potency products, which is undesirable from a public health perspective as higher potency products are associated with greater health risks, particularly for young or naïve users.14–16 Thus, if the goal of these regulations is to encourage moderate consumption of THC, lower limits need to be applied to quantity-based metrics, and regulators should consider shifting to limits based on quantity of THC. If the goal is to minimize risk of diversion from the legal market to the illicit market, states should also consider restricting the number of outlets a consumer can purchase from in a single day or specified time period, as Uruguay does. Such changes would do far more to promote moderate consumption and reduced diversion than current strategies that fail to achieve either.
ACKNOWLEDGMENTS
This study was supported by award R01AA026268 from the National Institute on Alcohol Abuse and Alcoholism (NIAAA). The content is solely the responsibility of the authors and does not necessarily represent the official views of NIAAA or NIH. NIAAA had no role in the study design; collection, analysis, and interpretation of data; writing the report; and the decision to submit the report for publication.
Footnotes
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