Toxic tokes

Let’s talk openly and matter-of-factly about pot: are pesticide residues on marijuana a health concern?

The truth is that we don’t know because there is virtually no research on the topic, and whether there are direct health risks posed by pesticides used in marijuana production will remain uncertain for as long as marijuana remains federally illegal. So, if you can’t bite into a fruit because of the allergic reactions that pesticides cause you or if you are looking for another argument for the legalization of your herbs, this column is for you.

Most people agree that pesticides have contributed to great gains in agricultural production and human nutrition. But while they can improve crop yield and quality of food, they also pose health risks to people — not to mention the risks they pose on the environment. And if anyone is to be aware of this fact, it should be North Carolinians who are third in the country in the number of pesticide-related illness and deaths, according to the Centers for Disease Control and Protection. (According to the Centers for Disease Control and Protection, North Carolina is the third state with the most pesticide-related illness and deaths with an average annual 34.55 per 100K illness and deaths between 2000 and 2010.)

When it comes to legal guidance over marijuana production and consumption methods, the absence of clarity on what’s legal and what’s not is particularly problematic. The simple confusion over the legality of pesticide use, has cost marijuana farmers across the country hundreds of thousands of dollars.

For example, earlier this summer, officials in Washington State ordered statewide halt to sales of 15 marijuana products after lab results showed these had residues of undisclosed pesticides. Also, last year, nine companies in Colorado were ordered to quarantine their plants because the Denver Department of Environmental Health found residues of Eagle 20, Mallet and Avid in their marijuana products. Were the farmers at fault? Many would argue that they weren’t.

The standard procedure for farmers caught using prohibited pesticides is that the contaminated crops are seized and destroyed. However, currently, there is no pesticide in the market that says “approved for marijuana”. That means that any grower in the country that uses some form of pesticide is at risk of losing her crop. By some estimates, 95% of cultivators nationwide do use some form of pesticide. That’s a lot of weed to burn just because somebody wanted to keep bugs away from their flowers.

But assuming the farmers were at fault, is it even worth it to burn all that hash in the name of toxicity prevention? How toxic is this stuff anyway?

In general, how toxic a pesticide is depends both on its residue levels and how it is ingested. At least for the case of edible marijuana products you can count on your liver to provide some protection, but for the case of smoked marijuana, the story is very different.

A 2013 study found that up to 69.5 percent of pesticide residues can remain in smoked marijuana. However, filtering smoke through cotton can reduce the level of pesticide residues to 1-11 percent. To give you a reference point, the analogous statistic for tobacco is 1.5-15.5 percent.

Some interests groups claim that quality cannabis can be grown with organic methods. In their view, cannabis growers could lead the way in developing a truly all-natural agricultural industry. However, not using pesticides poses financial costs on producers and other types of health risks on consumers.

In the case of producers take for example a small-scale marijuana farmer with 150 plants in Colorado. If some mildew infestation forced him to destroy a crop that would have yielded 70 pounds of cannabis, at the 2015 rate for retail marijuana, he would have easily lost $230,000. Maybe I’m just too poor, but if I were him, I think I’d spray my plants with a little Eagle 20 — particularly since there are no laws and no science saying that I shouldn’t.

Regarding the case of health risks to consumers, consider that molds and bacteria can contaminate cannabis plants too, and being exposed to those pathogens can be harmful to marijuana consumers. This would be a particularly serious concern for users of medical marijuana since their immune systems are already vulnerable.

The case has been exposed. Is it legal or safe to use pesticides on marijuana? Is it fair and financially sound to prevent pesticide use in marijuana production? I can’t answer that for you. But until pot is not legal at the federal level, I would recommend you adding a filter next time you roll.


“Cannabis growers look for clarity on pesticide use” (July 7, 2016):

“State finds undisclosed pesticides in pot growing products” (June 30, 2016):

“Pesticide use can pose health risks; how is it in your state? (Jun 10, 2016):

“The wild west of marijuana pesticides”. ( Aug 31, 2015):

“Marijuana Legalization 2015: EPA  Issues guidance on marijuana pesticides amid industry uncertainty”. (June 9, 2015):

“Confusion over pesticide rules presents conundrum for Colorado cannabis growers”. (April 23, 2015):

“Pesticide Use in Marijuana Production: Safety Issues and Sustainable Options As states legalize cannabis, toxics in cultivation intersect with health and the environment, and ecological practices” (2014-2015):



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