Ian Ayres is the William K. Townsend professor at Yale Law School.

The tragic epidemic of more than 100 overdoses in New Haven, Conn., last month had health workers literally scrambling from one patient to the next on my hometown’s central green.

These overdoses are better characterized as poisonings. The victims were exposed to tainted synthetic marijuana laced with Fubinaca, a powerful synthetic drug that mimics the effects of cannabis but is far more potent.

The problem has reached epidemic proportions because amateur chemists here and abroad find it easy to manufacture a host of deadly synthetics. Established approaches to drug-law enforcement are inadequate to deal with this flood onto the illegal marketplace. As Sen. Richard Blumenthal (D-Conn.) said: “We need new tactics to address synthetics.”

One option to consider: drug exchanges.

If needle exchanges can purge dangerous delivery devices from our streets, why not use a drug-exchange program to vacuum up the dangerous drugs themselves? State lawmakers should authorize public-health officials responding to the next tainted synthetic marijuana health emergency to trade cash or even marijuana for K2 — at least in states where recreational marijuana use is legal.

The current public-health approach is to get the word out that a bad batch of drugs is being sold in the area in the hope that drug purchasers will throw away their potentially tainted product. But the news from New Haven suggests that asking dealers and people with substance-use disorders to throw away their stash is sometimes too big an ask. The New Haven Register reported that several of the people who received initial treatment for the tainted K2 returned to the green wearing their hospital bracelets and overdosed again — some more than once.

Clearly, the demand for drugs persists even in the face of public-health warnings. Instead of asking addicts to give up probabilistically untainted drugs for nothing, public-health officials might, for a short time, offer people to trade for some mixture of money and pot.

Some of the New Haven victims would probably have turned down such offers as they actively sought the more powerful effect of Fubinaca. But possessors who mistakenly bought the tainted K2, and dealers who were reluctant to throw away their inventory, might be more likely to make a swap.

Fear of adulteration has never been greater; even seemingly organic buds can be sprayed with deadly enhancements. Student groups at several universities have responded by offering free “drug identification testing.” But it’s much easier for testing kits to identify that a substance contains, say, THC, than it is to assure a user that it doesn’t also include a dangerous additive.

Needle-exchange programs — which often provide clean needles and drug treatment programing without requiring program participants to turn in used needles — have been shown to reduce the spread of HIV without increasing the prevalence of substance-use disorder. A drug-exchange program is likely to be even more effective because cash and marijuana are safe substitutes to reduce the supply of the adulterated alternative.

The application of the drug-exchange idea to other drugs has far-reaching implications. Each year, hundreds of people mistakenly ingest PCP-laced marijuana or acid. More important, a substantial number of the nearly 30,000 overdose deaths involving synthetic opioids last year claimed the lives of people who didn’t know they were using drugs laced with fentanyl and its analogues — including the artist Prince, who died in 2016. These incredibly powerful synthetic opioids are increasingly mixed into illicit supplies of heroin, cocaine, methamphetamine and a class of anti-anxiety medicines known as benzodiazepines.

recent study among young adults in Rhode Island found that 11 percent of opioid users suspected they had been exposed to fentanyl through contaminated drugs in the prior six months. Many heroin users reported a strong preference to avoid using fentanyl, but the study found avoiding the chemical “difficult or impossible to achieve.”

Of course, it’s one thing for the government to hand out marijuana in response to a temporary emergency; it’s quite another to trade heroin on an ongoing basis. Like gun buyback programs, offering cash for fentanyl-laced drugs might reduce harm without turning the government into a supplier of smack. But the difficulty for an ongoing buyback program is finding a price that is sufficient to take the stock of adulterated product off the street — without incentivizing more supply of deadly substances in the future.

Lawmakers would be prudent to authorize an experiment rigorously studying the effectiveness of drug exchanges on an episodic basis, possibly just offering the public the option to trade some combination of cash and marijuana in a limited geographic area.

New Haven may be a harbinger of worse things to come. The synthetic-opioid-poisoning crisis has reached epidemic proportions — involved in almost triple the number of deaths as annual gun homicides. And the rising tide of more synthetics from more wholesale suppliers suggests that a synthetic crisis is already upon us. Helping people with substance-abuse disorder give up adulterated synthetics for less deadly highs might save lives.

Read more: