NIST Analysis Finds Most Tested Smokable Hemp Products Exceeded the Federal Total-THC Limit
An analysis of 53 smokable hemp products found that approximately 93% contained total delta-9 THC above the federal threshold used to distinguish hemp from marijuana. The products were marketed as federally compliant hemp, but testing by the National Institute of Standards and Technology (NIST) produced substantially different results.
The findings come from a 2024 study published in Forensic Chemistry by NIST researchers. The team examined products purchased from five commercial sources, measuring delta-8 THC, delta-9 THC, tetrahydrocannabinolic acid (THCA), and total delta-9 THC using liquid chromatography with photodiode-array detection.
Under the federal hemp framework, cannabis must contain no more than 0.3% total delta-9 THC by dry weight. Total THC accounts for both delta-9 THC and the potential conversion of THCA into delta-9 THC. The U.S. Department of Agriculture’s testing guidance uses the calculation THC + (0.877 × THCA) to estimate that total.
Although all 53 products were sold as hemp with stated delta-9 THC levels at or below 0.3%, NIST found that about 93% exceeded the limit when total delta-9 THC was measured. The result does not establish how common noncompliant products are across the entire hemp market: the samples came from only five commercial sources and were selected for analytical evaluation, rather than drawn as a representative national survey.
The researchers also found inconsistencies between laboratory measurements and manufacturers’ certificates of analysis. Online documentation was available for 45 of the products, but direct comparisons with NIST’s results were possible for only 22. The two sets of measurements agreed within their uncertainty ranges for approximately 55% of total delta-9 THC results, 68% of THCA results, and 18% of delta-9 THC results.
Several factors could explain the discrepancies, according to the study. Products may not have been sufficiently homogeneous from one package to another, contract laboratories may have used inaccurate or inconsistent measurements, and older certificates of analysis may not have reflected changes during storage. THCA can also gradually decarboxylate into delta-9 THC, potentially changing a product’s cannabinoid profile over time.
The study’s central concern is therefore not only whether individual products exceed the legal limit, but whether manufacturers, laboratories, regulators, and forensic analysts are measuring and reporting cannabinoid content consistently. That matters for product labeling, regulatory enforcement, and the classification of seized cannabis material.
NIST has since developed Hemp Plant Reference Material RM 8210, a standardized material that laboratories can use to check the accuracy of measurements for THC, CBD, moisture, and certain toxic elements. Such reference materials, along with better sampling procedures, validated methods, appropriate storage, and up-to-date certificates of analysis, could help reduce the gap between the cannabinoid content manufacturers report and what testing laboratories actually find.
