The vast majority of the opioid overdose deaths in Massachusetts this year have been associated with fentanyl, according to the state's Department of Public Health.

Bryce Pardo of the RAND Corporation has worked with national, state and local governments on crime and drug policy. Pardo spoke with WGBH Radio’s Jeb Sharp about fentanyl and how it’s finding its way to drug users here in Massachusetts.

Jeb Sharp: Bryce, most of us had never heard of fentanyl until pretty recently. What is fentanyl and what's it used for?

Bryce Pardo: Fentanyl has been around for about 60 years. It's a very potent, fast-acting synthetic opioid. It is something that's been used for quite some time in surgeries, as well as a very strong painkiller. In the last five or six years, it has started to make its way into the illicit drug market, heroin markets in particular. This is the fifth outbreak of fentanyl in illicit drug markets. The first was as early as 1979, but those earlier outbreaks were pretty much limited by the fact that chemists who could actually synthesize or manufacture fentanyl often didn't have the means with which to distribute it in illicit markets. And that's all changed in the last six years with the arrival of cheaply produced products coming from China.

Sharp: Give us a sense of that, how radical a change that is. What's happened globally for that to be possible?

Pardo: So as China has increased in terms of its export capacity, it's become the leading manufacturer of active pharmaceutical ingredients. But because they have such a massive industry and they have very little regulatory oversight, some producers are basically able to kind of skirt domestic law there and produce these new synthetic opioids, and export them to global markets. And this has only been aided by the fact that now with the internet, anybody with an internet connection and a mailing address can essentially import a substantial amount of powder fentanyl and then redistribute it into illicit drug markets here in the United States.

Sharp: The fentanyl that we see here in New England, is that coming through those online channels and mail?

Pardo: It's hard to say exactly, but a good part of the fentanyl that we see here in the United States is coming from China directly through the kind of legitimate postal system or express courier or consignment operators like DHL or FedEx. But there is another source of fentanyl, which is through Mexico. The Mexican drug cartels are synthesizing fentanyl, they have been in the last six years or so. At the same time, a lot of the primary inputs that they obtain, like the precursor chemicals, come from China. They are essentially illicitly importing precursors to Mexico, synthesizing fentanyl, trafficking it over the border, and then on through overland routes to make their way into drug markets here in United States.

The fentanyl problem in the United States is fairly concentrated in the eastern half of the United States, east of the Mississippi River. You look at places like Ohio, West Virginia, very hard hit by fentanyl, as well as New England. But then then you kind of scratch the surface, and you see that there's substantial variation in what is being seized. So like in Ohio, for example, about half of the seizures of fentanyl are just one single chemical: fentanyl. The rest is just a kind of a hodgepodge of other analogs, like carfentanyl. Whereas in contrast, in New England you see that it's predominantly, 90 percent or higher, just fentanyl. And so this suggests that there is some sort of variation in the supply channels.

Sharp: That's interesting. Anything else that's specific to Massachusetts or New England that we should know about?

Pardo: The case in point is New Hampshire. New Hampshire is probably the best example of this. In the last few years, we're seeing now pretty much a complete transition away from heroin towards fentanyl.

Sharp: What are the implications of that for trying to fight it at the local level?

Pardo: So that means we need to start thinking more innovatively about how to reduce the risk of overdose, like expanding access to naloxone is very important. Extracting individuals from these markets very quickly is also important. RAND last year put out a pretty substantial report looking at the evidence base regarding prescription heroin. This is a very controversial policy intervention, but there's some good research, randomized controlled trials, looking at individuals who have been assigned heroin versus individuals randomly assigned methadone. And when you look at the outcomes, indeed you see that individuals that are receiving prescription heroin — are given heroin, have to come in two or three times a day and receive the medication and use under supervision, they're on-site — you see that their health outcomes are improved, their psycho-social outcomes are better than those receiving methadone. And then furthermore, they stop sourcing heroin from the illicit street market. And that really is key here, since that's where the exposure to fentanyl is coming in.

Beyond these kind of harm reduction or treatment interventions, we could think about kind of disrupting supply here in United States as well. So, thinking about ways that law enforcement can try to deter or dissuade individuals from sourcing online, by maybe creating fake web sites that are made to mimic the kind of online vendors that are selling the product from China.