An increasing number of kids are showing up in emergency rooms across the U.S. with side effects from over-the-counter “synthetic pot” — a legal, marijuana-like substance sold in gas stations and corner stores. Poison control centers have received nearly 4,500 calls related to toxic effects of the drug since 2010, when the drug became widely available. HealthDay News reports:

The recent advent of so-called “synthetic pot” is a rising public health concern, researchers warn, sending kids to the emergency room and prompting parental calls to poison control centers.

The concoction was originally conceived in a laboratory setting as a research aid for animal studies involving THC, a key stimulative ingredient in marijuana, the new report noted.

But purely recreational street use of this widely varying mix of plants and herbal ingredients is growing. It’s widely available and is currently undetectable by commercial drug tests.

“The concern is that we’re going to really see this grow in popularity,” said study author Dr. Joanna Cohen, an assistant professor of pediatrics and emergency medicine at Children’s National Medical Center, in Washington, D.C. “Because it’s really easy to get, and because kids know that it doesn’t come back on typical clinically useful urine drug screenings that we would use in an ER.”

Read here for more about the dangers of this drug.