The prevalence of pesticides and contaminants in retail cannabis is one of the most important issues facing the industry. As more states require testing, the high levels of pesticides in retail products are causing alarm among consumers and regulators concerned about the potential health effects of these chemicals, especially on medical patients with compromised immune systems.

The extent of the problem was highlighted by Steep Hill Labs, a leading cannabis-testing company. It found that, if California implemented the same testing requirements adopted by Oregon, 84 percent of the products tested in the state would fail—an alarmingly high number for the country’s largest cannabis market. Nor is the pesticide problem confined to California: The Association of Commercial Cannabis Companies estimates that half of the cannabis tested around the country contains measurable levels of pesticides, though the exact number is still not known. As Jeffrey Raber, president of the ACCL, states: “Cultivating-agent contamination is a huge concern.”

Technological advances in testing have enabled us to see the true extent of the problem. As the ACCL reports, “Using state-of-the-art mass-spectrometry-based approaches, we have broadened the ability to detect more of these cultivating agents and have come to understand that this problem is larger and more complex than anyone initially suspected.”

One of the most prevalent pesticides, myclobutanil, is of particular concern in smoked forms of cannabis, because it turns into hydrogen cyanide—a compound that is toxic to humans—when combusted. Sixty-six percent of the cannabis samples tested in California contained myclobutanil, indicating its widespread use despite the health risks it poses.

The intensive use of pesticides in loosely regulated cannabis markets is understandable: The plant is highly susceptible to fungal infections that can damage entire crops, which can be extremely costly to growers. This leads some to overuse pesticides, resulting in residual levels in the harvested plants that far exceed what is considered safe for human consumption. A single joint of contaminated cannabis may not be enough to kill or cause severe harm, but the cumulative effects of ingesting contaminated cannabis may pose serious long-term health risks to cannabis consumers.

The increased focus on pesticides is being fueled by a greater interest on the part of consumers in the quality of the cannabis they purchase. In illicit markets, cannabis consumers had very little access to information about its source, its potency or its quality. With the transition to legal cannabis markets, especially those that now mandate testing, consumers are seeing for the first time the extent of the contaminant problem in cannabis, and are increasingly demanding more information on product quality.

Cannabis testing has become more widespread as recreational and medical marijuana states include testing requirements in their regulations. Under the newly passed adult-use law in California, for example, all cannabis will need to be tested before it reaches store shelves.

While the precise testing requirements have yet to be finalized, the extent of the pesticide problem revealed in Steep Hill’s analysis indicates that many growers will need to change their practices to ensure that their products can be sold. This may make it more challenging for growers, but the public-health concerns raised by unfettered pesticide use are too significant to ignore.

John Kagia is executive vice president of industry analytics for New Frontier Data.