Nearly two years ago, Beth Quinn’s son Brendan was found dead at age 48. He had apparently overdosed on kratom, an herb with opioid and stimulant-like effects that has earned it the nickname “gas station heroin.” Quinn blames the lack of regulation of kratom for the death of her son, who leaves behind a 15-year-old daughter.

“There was no dosage recommendation,” said Quinn, a former newspaper editor who lives in upstate New York. “There was nothing except, ‘It’s not our problem if you die, that’s on you, man.'”

Kratom is sold legally and widely in vape shops, gas stations and supermarkets in liquid, tablet or powder form. The American Kratom Association, which advocates for consumer access to the substance, says it’s an industry worth about $1.5 billion a year.

Kratom is not regulated as a controlled substance, although the Drug Enforcement Administration lists it as a “drug of concern.” The FDA has not approved kratom for any purpose, but dietary supplements do not require approval from the agency to be sold.

According to a report from the Centers for Disease Control and Prevention, kratom was the cause of 91 overdose deaths between July 2016 and December 2017. But some estimates put the numbers much higher: A Washington Post analysis found that kratom was listed as the primary or partial cause of death in at least 4,100 deaths between 2020 and 2022, and a Tampa Bay Times investigation last year found that more than 580 people have died of kratom-related overdoses in Florida alone since 2013.

In a letter published Monday in the journal Annals of Internal Medicine, a group of researchers called kratom an “emerging problem” and suggested that doctors should consider asking patients about their kratom use, as they do for cannabis, cocaine, methamphetamines or heroin. The article suggests that about 1.9 million people in the U.S. had used kratom in 2022, although the authors say that’s an underestimate.

The DEA attempted to temporarily reclassify kratom as a Schedule 1 substance in 2016, but changed that after a backlash. Instead of federal oversight, more states and cities are now taking action against kratom on their own.

A patchwork quilt

According to a report from the Congressional Research Service, at least six states — Alabama, Arkansas, Indiana, Rhode Island, Vermont and Wisconsin — had banned kratom entirely by the end of last year. Some cities have done so recently, too: Tinley Park, Illinois, a suburb of Chicago, enacted a ban in June. Newport Beach, California, did the same in May.

More common, however, are age-related restrictions. More than 15 states prohibit the sale of kratom to minors or anyone under the age of 21.

Kentucky recently joined the list: Last month, a law went into effect that bans the sale of kratom to anyone under 21, restricts the ingredients in kratom products, and requires ingredient disclosure on the label. In May, Georgia passed a similar law that tightens regulations on kratom products and raises the minimum age to purchase to 21. “When I started researching the substance, I realized that Georgians who used kratom weren’t fully aware of what they were putting into their bodies when they took it,” said Republican Rep. Rick Townsend, who introduced the bill.

Townsend said he was inspired to make the request after two voters told him they lost their son to kratom, among other things.

Oklahoma also recently passed a law requiring labeling for kratom products. The state has banned the sale of kratom to minors since 2021.

Rep. Daniel Pae of Oklahoma, who introduced the bill, said he was open to “federal uniformity” in regulating kratom, but “given the political realities in Congress, I don’t expect any action to be taken there any time soon.”

Oliver Grundmann, a clinical professor in the University of Florida’s department of medicinal chemistry, has been researching kratom since 2016. While stronger regulations are needed, a nationwide ban may not be advisable because the substance appears to help some people with opioid withdrawal, he said.

“There are legitimate uses for it, but it must be done in a controlled environment,” Grundmann said.

He added that due to a lack of federal regulations, there is also no mandatory reporting of deaths from kratom overdoses, making it difficult to reconstruct the effects.

“Basically, you have to look at the coroner’s reports or death certificates in each state,” he said.

The American Kratom Association said it would welcome more regulation. Mac Haddow, a senior fellow for public policy at the association, called the current industry a “Wild West.”

“Consumers should be on guard,” he said, adding that if the information on the label is missing or questionable, “the product should not be used.”

Four Groups of Kratom Users

Kratom contains a chemical compound called mitragynine, which can stimulate the same brain receptors as opioids. Experts say this makes it somewhat addictive. In high concentrations, the substance can cause nausea, cramps, vomiting, difficulty breathing, and in the most extreme cases, death.

The FDA has issued warnings about the health risks of kratom and taken action against manufacturers who make misleading claims. But given the general lack of regulation, the packaging of many kratom products does not include information about dosage, the concentration of active ingredients or the other ingredients mixed in. “Nobody wants to buy a product that is contaminated with lead, arsenic and tin,” said Michael White, chair of the pharmacy practice department at the University of Connecticut. “But I can tell you that there are a number of kratom products being sold right now that exceed FDA regulations… for all of these heavy metals.”

White categorized kratom users into four main groups.

The first group are people with opioid use disorder who buy kratom to tide them over until they can get more opiates or to wean themselves off of even harder drugs. The second group are people who say kratom helps them manage pain. Then there are users with anxiety, depression, or other mood disorders, and finally a group who simply enjoy the stimulant effects.

Emmy Hartman, a TikTok influencer who has posted about kratom, belongs to the latter group. She said she started taking it to help her focus.

“I drank it to do my taxes, and I had a great time,” Hartman said in an interview in June. “I felt relaxed, I felt a little happy. So I kept drinking.”

Hartman admitted that she didn’t know much about the ingredients in kratom when she first tried it.

“I called one of my friends and showed it to him. He said, ‘Emmy, did you read what’s in there?’ And I said, ‘No.’ He described it as ‘gas station crack.'”

Quinn doesn’t know why her son Brendan took kratom. He had struggled with drug and alcohol abuse, she said, and he also suffered from chronic shoulder pain after surgery. The toxicology report after his death, which NBC News reviewed, showed he had nothing in his system other than caffeine, nicotine, kratom and a prescribed anti-epileptic drug.

“We went into the house and found an empty box of kratom,” Quinn said. “Just because it’s sold in the supermarket doesn’t mean it’s safe.”

This article was originally published on NBCNews.com.