Wildfires are all too common in California, in fact, the state experiences an average of 3,600 wildfires every year. Most of these fires are relatively small and self-contained and are of minimal danger to human life and animal habitat, but when conditions are made ripe through extended periods of drought and the presence of the dry “Diablo winds”, some wildfires can grow to cover hundreds of thousands of acres, leaving a trail of destruction in their path.



16 major wildfires are currently active in the state, including the Mendocino Complex Fire. This fire is the result of the Ranch Fire and River Fire combining around the shores of Clear Lake in Northern California to create the largest single wildfire ever seen in the state’s history, currently covering over 283,000 acres of land and destroying 75 homes.



As well as affecting the homes of residents, the fires are also having huge effects on the Californian agriculture, including the cannabis industry. The Californian climate is famed for how it allows cannabis plants to prosper in outdoor farms, as well as the indoor greenhouses that are common in colder climates. As a result, many cannabis growers’ farms are at risk of direct fire damage to the crops. And, those who operate cannabis farms downwind of the fires are also having to contend with huge volumes of airborne soot contaminating their plants. Even indoor cannabis farms can be affected by airborne contaminants as they get drawn into ventilation systems and spread through the greenhouses.





Types of contamination from wildfires



The burning wildfires produce an array of different contaminants that can present many risks to the cannabis industry. In addition to losses from direct burning as wildfires spread, the large amounts of soot and ash produced by the burning trees can stress cannabis plants resulting in stunted growth or even plant death. In badly affected regions, this can wipe out a large portion of the cannabis crop in the county, potentially leading to inflated prices as cannabis farmers try to make ends meet and pay their workers with the profits of a much smaller crop.



It is challenging to remove all traces of soot contamination before cannabis is distributed for sale without the use of even harsher chemicals. Furthermore, even if the majority of the soot deposition can be removed from the surface of the plant, it is still likely to ruin the flavor for the consumer.



Wildfires do not remain contained to rural and wooded areas, they can also spread into towns and cities in the affected region. This is currently happening in the city of Redding, Shasta County, where residents are being evacuated as the Carr Fire reaches the city limits.



When the fires move into towns and cities, different airborne contaminants are produced by the flames. For example, many older timber structures were built with chromated copper arsenate wood in the interest of preserving the timber, but this treated wood can release toxic arsenic into the air upon burning. The wildfires are also hot enough to burn rubber and plastic, which can release benzene and other carcinogenic aromatic hydrocarbons into the environment.





Cannabis testing in polluted areas



The presence of contaminants produced during the fires is also putting a strain on the cannabis testing laboratories in California. Due to the federal restrictions imposed on cannabis as a schedule 1 drug, there is no federally recognized way to carry out quality control on cannabis plants and as a result, each state can impose its own individual testing criteria.



Current cannabis testing procedures are thought to be vulnerable to providing false-positive or false-negative results due to the interference of wildfire-related contaminants. While cannabis testing regulations in California include provisions for many of the most common pesticides, there is no framework in place for fire-borne materials. Ash and soot from burning wood is mostly made up of harmless carbon and as such is unlikely to affect testing results, but things like heavy metals and complex aromatic hydrocarbons from burning plastics and rubber could potentially avoid detection.



Additionally, if cannabis is grown near burning crops that have been heavily treated with pesticides, the combustion products of the pesticides can be carried downwind and settle on the cannabis plants. These trace combustion products may not be as dangerous as the original high volumes of pesticide, but as they have similar chemical structures they can be flagged during testing as dangerous pesticides and again lead to false positives and inaccurate analysis.



In California, cannabis testing is overseen by the Bureau of Cannabis Control. In an effort to create a more accurate and reliable cannabis testing system, the Bureau is currently in the process of rolling out new testing standards and guidelines for cannabis. Many of these new criteria will include provisions for fire-affected crops. For example, as part of the final phase beginning in January 2019, all cannabis testing facilities in California will be required to test for heavy metal contaminants, such as arsenic, as part of standard testing. The second phase, which is currently being implemented, includes the need for more advanced pesticide residue tests, which may also improve the accuracy of cannabis testing in regions affected by wildfires.