An industrial chemical is creeping into Philly's fentanyl supply

• While the chemical's health effects on humans aren't known, studies using rats have shown it can cause heart defects, lung damage, blurry vision and death.

Driving the news: About 17% of fentanyl samples collected in Kensington, one of the East Coast's biggest open-air drug markets, over a four-month period last year contained BTMPS — shorthand for an industrial chemical that's often added to plastics and other polymers, Columbia University researchers found.

• Plastic manufacturers typically add BTMPS to protect their products against heat and sunlight.

The intrigue: The average sample contained about twice as much BTMPS as fentanyl (4% compared to 2.3%), with one containing 18% BTMPS — far exceeding levels people are normally exposed to from plastic products, per the study published last month.

Flashback: Philly health officials put out a warning late last year after BTMPS was discovered in the Philly drug supply, saying it's still unclear whether the chemical increases the likelihood of overdoses.

• Philly officials said BTMPS was initially discovered last June in about a quarter of their samples, but by November, that number had jumped to 55%.
• People who have reported smoking BTMPS-laced fentanyl said it smelled like bug spray, while those who've injected it said it burned, per the city.
• Additional observed effects include ringing ears, blurred vision and a bloody cough.

By the numbers: Philly had more than 1,300 overdose deaths in 2023, fueled largely by opioids, including synthetic fentanyl. They were down 7% from 2022, the first decline in five years.

• The animal tranquilizer xylazine has also increasingly infiltrated the city's illegal heroin market over the past few years, which has been linked to overdoses.

Zoom out: The findings, published in JAMA, are part of a larger study by a team of researchers who tested samples from nine sites in California, Pennsylvania, Delaware, Maryland, Nevada, Washington and Puerto Rico.

• BTMPS was found in all locations, typically in greater amounts than fentanyl.

What they're saying: The same drug additive rarely appears simultaneously in the U.S. drug supply, Columbia researchers Karli Hochstatter and Fernando Montero write.

• That means it's likely BTMPS is being used to manufacture fentanyl rather than just being added to the drug supply as a cutting agent.

Savage Sisters, a Kensington-based recovery nonprofit that helped local researchers obtain drug samples, was first warned of BTMPS from other harm reductionist groups across the U.S., executive director Sarah Laurel tells Axios.

• After finding traces of BTMPS here, Savage Sisters talked to Philly's street dealers who had "no idea what we were talking about," Laurel tells Axios.
• "We're all talking through this together: Is it something that's being adulterated into the supply? Was it being added to the bricks to preserve it through the trafficking spaces?" Laurel says.

The latest: Philly police have only detected two cases of BTMPS in 2025, Nicole Martin, chemistry lab manager at the city's Office of Forensic Science, tells Axios.

• But officials acknowledge numbers could be skewed since BTMPS isn't currently a controlled substance, so suspected drug samples aren't specifically tested for the chemical.
• Philly's forensic team says identifying new drug trends is a game of whack-a-mole, with dealers always looking to stay ahead of authorities.

What's ahead: Researchers are monitoring the BTMPS trend in Philly and plan to study immediate and long-term health consequences for people exposed to the chemical through drug use.

The bottom line: "My biggest concern is the unknown," Laurel says. "This one is a mystery."