With cannabis being regulated at the state level of the 39 states that have legalized at least medical marijuana, there are dozens of variations on the requirements for pesticide and other chemical contamination testing, inspection, and enforcement. That variation has become a point of contention for consumer safety across jurisdictions since there is little agreement on the contaminants that should be tested in legal markets, and the relative unknowns in the black market, which continues to exist. Criticism is rising in a number of states, such as California, that contamination is not being adequately addressed by those with oversight responsibilities.
As found in a 2022 study, a total of 679 cannabis contaminants are regulated by the states with legalized use, but each individual state generally regulates less than 20% of those. This means that a chemical that results in a recall in one state may not even require testing in another state. In fact, the study notes that five jurisdictions did not list any specific contaminants at all in their regulatory documents.
Of the contaminants regulated, pesticides were the most common, making up more than 80% of contaminants for which the states required testing. However, many of the pesticides listed “were highly unlikely to be used in cannabis cultivation and processing,” (e.g., chlorpropham, oxytetracycline, and norflurazon).
Not only did the study find that the regulated contaminants varied, but also the action levels. A case in point was that of heavy metals (including arsenic, cadmium, lead, and mercury) listed as contaminants by 28 jurisdictions, but the action levels varied significantly, ranging from 0.00009 ppm to 10.0 ppm.
In addition to providing statistics for all states with legalized marijuana at the time of the study (2022), the researchers delved specifically into contaminant load in California cannabis samples, the largest cannabis market in the US, where cannabis and its products are required to be tested for 68 pesticides, 4 inorganics, 20 solvents, 6 microbes, and 5 mycotoxins. The study results, showing that 5.1% of the cannabis samples tested exceeded California’s regulatory action levels, followed an earlier 2017 survey that found cannabis samples from dispensaries in California to contain significant numbers of fungal and bacterial contaminants.
It is numbers such as these, along with an investigation by The LA Times that found widespread contamination in California cannabis products and overall criticism that the state is failing to fully address contamination in cannabis, that triggered a late February 2025 request that the California governor and legislature shift responsibility for pesticides in cannabis products from the Department of Cannabis Control to the state Department of Pesticide Regulation. The request from the Santa Cruz County Board of Supervisors also asked that accreditation of cannabis testing labs be moved to the State Water Resources Control Board, and that 24 pesticides be added to the list of 66 chemicals for which cannabis products must be screened for prior to sale.
With such a range of contaminant regulations, action levels, and safety issues, TAG continues to see federal oversight as needed to overcome the many challenges of state-by-state regulation. Thus, we would agree with the conclusion of the 2022 study noting that it demonstrates a “need for a unified regulatory approach to mitigate the public health risk of cannabis contamination at a national level”; and that the national-level guideline should be based on a human health risk assessment and include a rigorous approach to regulate medical cannabis to address the vulnerabilities of these populations.
