A growing coalition of U.S. politicians want tougher police tactics used against gangs now selling fentanyl, methamphetamines and xylazine.

"We do need to stop the trafficking of these drugs and give law enforcement the tools they need," said Nevada's Democratic Sen. Catherine Cortez Masto, lead sponsor of a bill to toughen penalties for dealing the synthetic drug xylazine.

Big drug sweeps, narcotics seizures and mass arrests of dealers have been a cornerstone of America's war on drugs since the 1970s.

But new research published in the American Journal of Public Health suggests
drug busts and police crackdowns on dealers may actually be making the overdose crisis worse.

The study, which underwent a rigorous peer-review process because of its controversial findings, is based on data gathered in Indianapolis, Indiana that found patterns of overdose and death that followed drug seizures in the city.

"With opioids we saw overdoses double in the area immediately surrounding a seizure, within maybe a five-minute walk of that seizure over the next several weeks," said Jennifer Carroll, a medical anthropologist at North Carolina State University and co-author of the article.

What happens after you arrest a drug dealer?

Law enforcement agencies have argued for years that arresting dealers and disrupting the supply of street drugs would make communities safer.

Lawmakers in state houses and Congress have raced to boost funding for drug interdiction, while toughening criminal penalties for trafficking fentanyl.

"We can't just allow the drugs to come in because we are seeing too many deaths," Sen. Cortez Masto told NPR.

Are harsher fentanyl sentences the solution to the opiate crisis? Experts say no

But Carroll says a growing body of data, including her own study, shows drug sweeps and seizures can destabilize the ecosystem of illegal activity.

People with addiction wind up buying fentanyl, methamphetamines and other high-risk street drugs from strangers selling drugs of different potency — often with different, more dangerous ingredients.

When people experiencing severe addiction are forced to go without drugs — even for a short period of time — it can alter their level of tolerance. Begin using again and they may be more vulnerable to overdose and death.

"When supply is disrupted, demand does not decrease," Carroll noted. "It's really drug market disruptions that are driving a lot of the harm of illicit substance use."

Brandon Del Pozo is a former police chief who now studies drug policy at Brown University. He's one of this new study's co-authors and says evidence is now clear that drug-bust tactics put lives at risk without actually cleaning up neighborhoods.

"There's a long history of big drug arrests followed by press conferences that say, 'This time will be different, this time will make a difference,'" Del Pozo said. "But except in the short term, where it leads to more overdose, it hasn't made a difference."

Research raises questions. Politicians call for tough action

Indeed, many of these tactics have been in use for half a century, but critics say they haven't worked.

The supply of street drugs is now cheaper, more readily available, and more toxic than ever before; roughly 110,000 people in the U.S. died of fatal overdoses last year alone, a devastating new record.

"If the goal is to save lives, we have pretty good reason to save lives, then we have pretty good reason to believe that criminalization really isn't serving that purpose very well," Carroll said.

But fear of fentanyl is adding to political pressure to get even tougher on drug dealers.

"I don't see the enforcement side of it slowing down at all, many people are doubling down," said Brittney Garrett, a former cop who now advises police departments on drug fighting tactics.

Sen. Cortez Masto describes her xylazine measure - which has broad bipartisan support - as a necessary legal tool to toughen penalties and "crack down on traffickers."

"I can just tell you what I'm seeing and hearing from my law enforcement," Sen. Cortz Masto told NPR. Xylazine is "becoming an emergent threat, one we need to get a handle on now and not wait to lose more lives."

Beau Kilmer, who heads the Rand Drug Policy Research Center, agrees police should play a major role cleaning up neighborhoods where drug-dealing is rampant.

"If you can just reduce the number of dealers on the street and allow residents get their neighborhood back that could be a real benefit," he said.

Can drug seizures be folded into a wider public health strategy?

But Kilmer says this study shows that before drug busts and seizures occur, police have to do more planning to prevent spikes of deadly overdoses.

"They're going to want to make sure they talk to folks at the department of health and make sure they have a thoughtful plan making sure treatment is available," Kilmer said.

Some experts say this kind of coordination, while increasing, remains rare.

NPR asked the U.S. Drug Enforcement Administration and Indianapolis police for an interview about this research to find out how these findings might shape their tactics. The DEA didn't respond.

Indianapolis police sent a brief statement saying they would review results from the study but remain committed to taking drugs off the streets.

"We look forward to working with other law enforcement agencies, health care providers and other organizations who are committed to reducing drug trafficking and substance abuse," said Indianapolis police spokesperson Alexa Boylan in an email.

Just days after the new study was published, cops across Indianapolis — working with the DEA — mounted another major drug sweep, seizing roughly two hundred pounds of fentanyl and methamphetamines.

"I think what you see here today sends a message to our community, we are unyielding, said Indianapolis Deputy Police Chief Kendale Adams.

He didn't mention the overdose study or its warnings but said police are partnering with public health agencies.

"We'll be working with [the Office of Public Health and Safety] going back to some of these neighborhoods to see what they can do to change people's lives, change people's mindset, so they can get out of the game."

Some experts on police drug enforcement tactics believe law enforcement must do much more to protect public health before drug seizures occur. That would mean more advanced planning and coordination with harm reduction groups and others focused on helping people with addiction.

"We don't have a choice is the way I look at it," said Brittney Garrett, the former cop who works now with a pro-reform group called the Police Assisted Addiction and Recovery Initiative.

"By not having law enforcement, public health, behavioral health, harm reduction all working together, we're going to end up with more people being harmed."