The substance also known as K2 (a.k.a. 'synthetic marijuana') is becoming increasingly problematic in the nation's capital.

Over the course of 12 days, DC Fire and EMS received 463 calls for suspected K2 overdoses, with 340 people ultimately being admitted to hospital while other cases have proven fatal. The exact cause is yet unknown, but the Office of the Chief Medical Examiner "heavily suspects" these cases are linked to K2 consumption.

Douglas Buchanan, spokesperson for the DC Fire and EMS Department says this is an issue that is cross all social boundaries.

"It's not just near homeless shelters," Buchanan told NPR.

The cheap and largely inconspicuous substance can be easily found in DC: "It's sold at gas stations, corner stores and tobacco shops" says David Barnett, a food delivery driver. "I see the empty wrappers everywhere" he noted, adding that he sees people overdosing regularly as he makes his deliveries.

"I've seen people overdosing in Adams Morgan, Columbia Heights, the H Street corridor," he said, "and a couple of days ago I saw paramedics helping a woman outside of Union Station."

K2 is not actually marijuana. The drug is developed to stimulate the same areas of the brain that are affected by cannabis, so people call it synthetic marijuana. But K2 should not be confused with its significantly safer namesake.

"The contents of synthetic cannabinoid products can be unpredictable" explained Tegan Boehmer, a senior research scientist at CDC's National Center for Environmental Health in Atlanta. "The concentration of the active ingredient(s) can vary significantly between batches or even within the same batch."

K2 is typically comprised of legal compounds. The specific ingredients frequently change as manufacturers adapt their product to skirt around new regulations designed to crack down on the drug. Those alterations make the side effects of K2 extremely unpredictable and unsafe.

"You have no idea what you're buying and it's not in any way controlled when it's made," explained Dr. Jenifer Smith - Director of the Department of Forensic Sciences in Washington, DC. "It's very, very dangerous."

The problems with synthetic marijuana are not unique to DC either. CDC data suggests that Illinois, Wisconsin and Maryland have the highest rates of reported cases since March. And there have been 8 confirmed deaths associated with use of the substance across the country over the course of this month.

Cannabis for Beginners - How long does cannabis stay in your system?