Heavy Metals Found in 90 Percent of Tested Rolling Papers, Californian Study Finds

A new investigation of cannabis rolling papers available in California has found traces of heavy metals in 90 percent of products.

Carried out by the Californian branch of SC Labs, the investigation also found detectable amounts of pesticides in 16 percent of the samples, and five percent registered over the allowable action limits.

The extent of the contamination

SC Labs initiated the tests after one customer reportedly received pesticide traces in their finished products. Shortly after, a second customer reported a similar issue.

Both complaints were made despite the cannabis having previously passed a pesticide screening test.

“We had this cluster of customers that were batch testing pre-rolled joints and failed compliance testing for chlorpyrifos,” Josh Wurzer, president and co-founder of SC Labs, told Analytical Cannabis.

“All of these customers had pre-tested their plant material and it came up totally clean for all pesticides before rolling them into the joints and submitting them for this batch testing. So, obviously, everyone was a bit surprised and curious as to where the contamination came from.”

After further analysis, the contamination was traced back to the rolling papers used for the products. As the investigation report says, SC Labs then decided to embark on this wider analysis to “assess the frequency of detection and measure the levels of contamination” in rolling paper products in general.

In total, the study tested over 110 different rolling paper products available online and in local Santa Cruz smoke shops, including rice paper-based rolling papers, hemp- or cellulose-based rolling papers, pre-rolled cones, and wraps.

Notably, all three of the cellulose-based rolling papers exceeded the action limits for heavy metal detections; each type contained concerning amounts of lead.

Around 22 percent of the wraps tested also returned heavy metal test results that were above the action limits for California, although not to the same extreme levels seen with the cellulose-based products.

As many of these wraps were hemp-based, the team at SC Labs believe that the amounts of heavy metals detected are likely a result of hemp’s natural tendency to draw up nutrients from its surrounding soil, which then accumulate in the plant’s shoots and leaves.

In total, 58 percent of the wraps contained some levels of pesticides; 21 percent exceeded the state action limits for the relevant pesticide.

What does this mean for the consumer?

While these numbers might appear worrying on the surface, the scientists at SC Labs believe the results to be much more nuanced than they might first appear.

“I want to caution people to not be too alarmed over this report,” said Wurzer. “The takeaways that I have from this is that there are certain rolling paper categories that have much more contamination – or appear to have much more contamination based on this report – than others.”

The cellulose-based papers are of central concern, he says. While none of these products contained detectable limits of pesticides, the amount of harmful lead found in the products is still worrying.

“The cellulose-based rolling papers came in thousands of times over the inhalable limit for lead, basically maxed out the calibration on our instrument,” Wurzer explained. “As a consumer, I would be very wary of those products in particular – and until more data came back – I would say cellulose-based rolling papers as a category.”

For other rolling paper product types, the final products are likely still safe to consume. Rolling papers only contribute a fractional amount to the overall mass of any pre-roll product, and assuming that the cannabis plant material is free from contaminants, the final product would likely be still well under the actionable contaminant limits, even in states with very tight limits, like California. Although for products like the wraps, a significant portion of which returned positive pesticide and heavy metal detections, it may still be reasonable for consumers to take some caution.

“I would maybe be wary that if I consumed a lot of these wraps every day that maybe I’d want to cut back,” Wurzer recommended.

“I’d treat it sort of like how we treat some types of fish that are known to have high levels of mercury. You just limit your intake as a consumer.”

Wurzer’s report says that consumers should be made aware that rolling papers are not currently regulated like cannabis. Producers of pre-rolled products should also be aware that these rolling papers may be a potential liability when it comes to batch testing, and product manufacturers may wish to re-evaluate their product quality specifications to ensure that what they are producing is as clean and as safe as possible.