A team of researchers with Complutense University just published the first scientific study of the cannabis resin, i.e. hash, sold illegally on the streets of Madrid, Spain. And their findings suggest that street hash poses a major public health risk, both for the people handling it and those smoking it. According to the report, most, as in 88.3 percent of the 90 hash samples researchers obtained, were not suitable for human consumption due to the presence of feces and other contaminants.

Hash in Madrid is Sh*t—Literally

An alarming new report from forensic scientists in Madrid has found that most illegal cannabis products sold there are contaminated with human fecal bacterial. According to lead researcher and Pharmacist Manuel Pérez Moreno, the way drug traffickers smuggle and handle hash is responsible for the contamination.

Due to Spain’s strict prohibition against cannabis, much of the hash sold on the streets of cities like Madrid is smuggled in. For drug traffickers, there’s a simple way to do that. Just wrap a small amount of hash in some plastic and swallow it. Then when the coast is clear, take some laxatives to retrieve the stash. “And that’s what goes on sale,” Moreno said.

Dealers typically sell hash in two quantities: a larger unit, called an “ingot,” and a smaller unit, called an “acorn.” While one could conceivably swallow and pass both sizes, the acorn is much more manageable in that regard. And that likely accounts for the disparities in contamination researchers observed between the two types. Comparing the two, researchers found that 93 percent of the “acorns” tested positive for E. coli bacteria. But just 29.4 percent of the ingots sampled contained E. coli.

Escherichia coli bacteria live in the intestines of mammals. Most are harmless, part of our natural microbiome, but some are extremely dangerous. E. coli infections can cause serious bouts of diarrhea, severe abdominal and muscle cramps, vomiting and even hemorrhaging.

And the hash samples researchers analyzed didn’t just contain traces of fecal bacteria. They contained significant quantities. According to Pérez’s report, each gram of cannabis resin contained roughly 500 times the maximum amount of E. coli allowed by U.S. marijuana regulations. (Yes, there is a threshold for “acceptable” amounts of microbial contamination in regulated cannabis products.)

Without Access to Legal Medical Cannabis, Patients Turn to Dangerous Street Hash

Furthermore, the study found that 10 percent of all the hash samples contained a species of mold, aspergillus, that can trigger serious infections, especially in people with weakened immune systems. In other words, exactly the kind of people who are seeking cannabis products on the street to treat various conditions.

According to Spain’s Ministry of Health, 31 percent of the country’s population between the ages of 15 and 64 self-reported using cannabis at least once. And as the popularity of therapeutic and medicinal uses for cannabis continues growing worldwide, more Spaniards are looking to buy some. But illicit street products are typically their only source. “In recent years, there has been an increase in the number of people with cancer who smoke cannabis with the intention of reducing the side effects of chemotherapy,” Pérez cited as just one example.

But chemo patients and other people with illness are especially vulnerable to microbial contamination in hash. For them, street hash is a serious, potentially harmful risk.

Of course, fecal bacteria and mold pose risks for recreational consumers, too, beyond the yuck factor. Most people smoke hash in a spliff, rolling it up with tobacco and smoking it. If people use a filter at all, it’s likely hollow. And that means, as Pérez explained, “not only do you suck the smoke, you also suck particles”—as in, poop particles.