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Consider this sequence of numbers: 5, 7, 9. Can you spot the pattern? Here’s another with the same pattern: 15, 19, 23. One more: 232, 235, 238.  

“Three equally spaced things,” says Raghu Meka, a computer scientist at UCLA. “That’s probably the simplest pattern you can imagine.”  

Yet for almost a century, mathematicians in the field of combinatorics have been puzzling out how to know whether an endless list of numbers contains such a sequence, called an arithmetic progression. In other words, is there a way to be mathematically certain that a set contains a sequence of three or more evenly spaced numbers, even if you don’t know much about how the numbers in the set were selected or what the progression might be? 

Progress on the question has been slow, even plodding. But last year, Meka and Zander Kelley, a Ph.D. computer science student at the University of Illinois Urbana-Champaign, surprised mathematicians by making an exponential leap. The researchers are outsiders in combinatorics, which is concerned with counting configurations of numbers, points or other mathematical objects. And the duo didn’t set out to tackle the mystery of arithmetic progressions.  

Kelley and Meka were instead investigating abstract games in computer science. The pair sought a mathematical tool that might help them understand the best way to win a particular type of game over and over again. “I’m super-interested in a collection of techniques that fall under this umbrella called structure versus randomness,” Kelley says. Some of the earliest progress on arithmetic progressions relied on such techniques, which is what led Kelley and Meka to dive into the topic. 

The mystery of whether arithmetic progressions will show up is just one of many mathematical questions related to order versus disorder in sets of objects. Understanding order — and when and where patterns must emerge — is a recurring theme in many branches of math and computer science.  

Another example of order in objects says that any group of six people must contain either a group of at least three mutual acquaintances (all three know each other) or a group of at least three complete strangers (no one knows another). Research has shown that it doesn’t matter who they are, where they are from or how they were selected. There’s something powerful, maybe almost spooky, about the fact that we can say this — and make other similar claims about structure in sets — with mathematical certainty. 

Solving the mystery of arithmetic progressions might open doors to investigating more complex relationships among numbers in a set — gaps that change in more elaborate ways, for instance. “These are more sophisticated versions of the same theorems,” says Bryna Kra, a mathematician at Northwestern University in Evanston, Ill. “Typically, once you see arithmetic progressions … you see other patterns.”  

After publishing their work on arithmetic progressions, Kelley and Meka, with Shachar Lovett of the University of California, San Diego, imported techniques from their investigations of arithmetic progressions into a different context. The researchers solved a question in communication complexity, a subfield of theoretical computer science concerned with transmitting data efficiently between parties who have only partial information. 

What’s more, knowing that certain mathematical structures have to appear in certain situations can be useful in real-world communication networks and for image compression. 

Potential applications aside, researchers who study arithmetic progressions — or other facets of purely theoretical mathematics — are often motivated more by sheer curiosity than any practical payoff. The fact that questions about such simple patterns and when they appear remain largely unanswered is, for many, reason enough to pursue them. 

What are arithmetic progressions? 

Let’s take a moment to get our hands on some sets of numbers and the arithmetic progressions those sets contain, starting with the prime numbers, perennial favorites of math enthusiasts. A prime number is any whole number divisible only by itself and by 1; the first 10 primes are 2, 3, 5, 7, 11, 13, 17, 19, 23 and 29. Within those numbers, we can find a few arithmetic progressions. The numbers 3, 5 and 7 form a three-term arithmetic progression with a gap of two. But the numbers in a progression don’t have to follow each other immediately within the larger set: The numbers 5, 11, 17, 23 and 29 form a five-term arithmetic progression with a gap of six. 

Within a finite set of numbers, it’s straightforward to determine whether there are any arithmetic progressions. It might be tedious depending on the set, but it’s not mysterious. For infinite sets of numbers, though, the question gets interesting.  

The primes go on forever, and mathematicians have asked many — and answered some — questions about arithmetic progressions within them. Is there a longest possible arithmetic progression, a cap on the number of terms, in the primes? Or, can you find a progression of any finite length if you look long enough? In 2004, mathematicians proved that the latter is true. But questions including how far along the number line you have to look to find an arithmetic progression with a given number of terms or a given gap size remain active areas of research, for the primes and for other sets. 

The primes contain infinitely many arithmetic progressions, but some infinite sets contain none. Consider the powers of 10: 1, 10, 100, 1,000…. The gaps between consecutive terms get bigger fast — 9, 90, 900…. And none of them are the same. Playing around with the numbers a bit, you can convince yourself that no two powers of 10, whether consecutive or not, have the same gap as any other pair. 

With that context, we now approach a question at the heart of this research: Why do some sets have arithmetic progressions while others don’t? One big difference between the primes and powers of 10 is that there are a lot more primes than powers of 10. Sort of. Both sets are infinite, but if you pick any arbitrary number as a cutoff and look at how many primes or powers of 10 there are below that number, the primes win every time. There are four primes from 1 to 10, versus only two powers of 10. There are 25 primes from 1 to 100 and only three powers of 10. The primes don’t just win every time, they win by a lot, and the amount they win by keeps increasing. In this way, the primes are “denser” — in an intuitive and technical sense — than the powers of 10.  

A sparse enough set of numbers can have gaps arranged in ways that manage to avoid arithmetic progressions. Too dense, though, and the set can’t avoid having gaps that match up. In the 20th century, mathematicians settled on a way to measure that density. They are now looking for the density above which arithmetic progressions must appear. 

Density in infinite sets

The study of arithmetic progressions in sets of whole numbers began in earnest in 1936, when Hungarian mathematicians Paul Erdős and Pál Turán posited that any set of whole numbers that is dense enough must contain arithmetic progressions of any desired length. 

For finite sets, it’s easy to understand what density is. In the set of whole numbers between 1 and 10, the primes have a density of 4/10, or 0.4. But if we want to understand the density of the entire unending collection of prime numbers within the entire unending collection of the whole numbers, we need to find a way to make sense of infinity divided by infinity, or ∞/∞.  

Mathematicians use a concept called asymptotic density to wrangle with the density of an infinite set of whole numbers. The basic idea is to choose some number as a cutoff point, N, and see what happens as N increases. If the density tends toward some fixed number, that is the set’s asymptotic density.  

Let’s return to the powers of 10, whose density decreases across the number line. As you go out farther and farther, the proportion of whole numbers that are powers of 10 approaches zero — so the set has an asymptotic density of zero. Other sets have a positive asymptotic density, and some never settle down into an asymptotic density at all.  

What Erdős and Turán proposed is that any set of numbers with positive, rather than zero, asymptotic density must contain at least one arithmetic progression. For some sets, it’s obvious (the even numbers have an asymptotic density of 0.5 and definitely contain arithmetic progressions). But proving it for any arbitrary set of numbers turned out to be a challenge. 

It wasn’t until 1953 that German-British mathematician Klaus Roth proved the conjecture, opening the door to a more nuanced understanding of the role density plays in arithmetic progressions. He showed that any set with positive asymptotic density must contain at least one three-term arithmetic progression, or 3-AP. His argument relied on proving that dense enough pseudorandom sets — those that might not truly be chosen randomly but have the general properties of random sets — must contain arithmetic progressions. Then he developed a way to zoom in on parts of non-pseudorandom sets and show that, if the initial set is dense enough, these zoomed-in areas must be structured in ways that guarantee the presence of an arithmetic progression.  

In early 2021, Kelley and Meka were investigating a problem in complexity theory called parallel repetition of games. Don’t think Monopoly or chess; the “games” the researchers were thinking about won’t be making Hasbro money any time soon. “We have a tendency to call anything a game if it has turns,” says Kelley. In the typical games Kelley and Meka were looking at, the players have access to different information and have to work together to find an answer to a question. But they can’t communicate during the game, so they must decide on a strategy beforehand. Kelley and Meka sought to determine how to maximize the chances that the players win many games in a row. 

It’s not quite a hop, skip and a jump from parallel repetition of games to arithmetic progressions, but Kelley and Meka got there fairly quickly. “Maybe in a month we were at the 3-AP problem,” Meka says. Previous research on parallel repetition of games had used structure versus randomness arguments. Because Roth’s work on arithmetic progressions was the first to use such a technique, Kelley and Meka were interested in that work in its original habitat. 

“In theoretical computer science, people are looking outward to math for some tools that they could use, and unless you’re ready to get yourself into some serious trouble, usually you see if you can use the tools, and then if you can’t, you move on,” Kelley says. “You don’t try to go open them up and see what they’re like.” But he and Meka did just that, knowing that they might go down a deep rabbit hole and end up with nothing to show for their time and effort. They dug into Roth’s arguments — as well as more recent research on the same subject — to see if they could push the work further. And so they found themselves staring down arithmetic progressions. 

Reaching new limits 

Roth’s contribution was more powerful than just showing that any set with positive asymptotic density must contain a 3-AP. He also proved that some sets with asymptotic density of zero, if the density tends toward zero slowly enough as you go out along the number line, must also contain at least one 3-AP.  

Think of the density as having to pass beneath a limbo bar. If a set gets sparse too slowly, it can’t make it under and it must contain an arithmetic progression. But a set that approaches a density of zero quickly enough ducks under. For that set, anything goes: It may or may not have such a progression. 

Roth’s initial proof found an upper limit to where the limbo bar must be. He showed that any set whose density approaches zero at a rate similar to or slower than the expression 1/log(log(N)) must contain at least one arithmetic progression. Log means to take the logarithm, and remember that N is the number chosen as the arbitrary cutoff in an infinite set. We’re considering what happens as N increases.  

Logarithms grow slowly, roughly akin to the number of digits a number has. The logarithm of 1 is zero, of 10 is 1, of 100 is 2, of 1,000 is 3, and so on. But taking the logarithms of those logarithms gives much more sluggish growth. To nudge log(log(N)) from zero to 1, we have to move N from 10 to 10 billion. Dividing 1 by this double log, as appears in Roth’s work, we get a density that just plods toward zero. 

Several years earlier, in 1946, mathematician Felix Behrend had investigated the lower limit of the limbo bar. He developed a recipe for cooking up sets without 3-APs, showing that any such set must be extremely sparse indeed. His limit was a density that goes to zero at approximately the same rate as 1/e^{(log(N))^½}. That expression might not look familiar, but there’s an exponential function in the denominator. The log and ½ power slow things down a bit, but the whole expression goes to zero much faster than the double log Roth later found. 

In the last few decades, researchers have been attempting to close the gap between Roth-style estimates of the sparsest sets that must contain a 3-AP and Behrend-style estimates of the densest sets that do not contain one. In 2020, mathematicians Thomas Bloom of the University of Oxford and Olof Sisask of Stockholm University broke what had come to be known as the logarithmic barrier for the Roth-style upper limit of the limbo bar, showing that any set with a density that goes to zero more slowly than 1/log(N) must contain at least one 3-AP. The work was seen as a breakthrough in the field, though the upper limit was still closer to the previous best-known upper limit than to Behrend’s lower limit.  

Kelley and Meka pushed the upper limit down dramatically. Their result was a rate that goes to zero at approximately the same rate as 1/e^{(log(N))^1/11}. That formula looks eerily similar to Behrend’s lower limit. For the first time ever, the upper and lower limits are within shooting distance of each other. Closing that gap would reveal the specific location of the limbo bar and thus give a clear answer to which sets must contain at least one 3-AP. 

What’s next? 

When Kelley and Meka started on the 3-AP problem, they thought they would probably just poke around to identify the barriers to moving the upper limit down. A year later, the two were writing a paper about their breakthrough. “I think one thing that kept us going was it never felt like we were completely hitting a wall,” Meka says. “It always felt like we were either learning something useful, or we were actually making progress.”  

Meka describes their overall approach, based on Roth’s early techniques, as exploiting a “wishful dichotomy” between randomness and structure. They developed a definition of pseudorandomness for their work and showed that for this definition, any dense enough pseudorandom set must contain at least one arithmetic progression. 

After handling the pseudorandom case, the team considered more structured sets of numbers and showed that those sets too had to exhibit the desired patterns. Finally, Kelley and Meka expanded from these types of sets to all large enough sets of numbers, proving that those sets must have the properties of either the pseudo­random or the structured sets.  

“Three equally spaced things. That’s probably the simplest pattern you can imagine.”

Raghu Meka

The most remarkable thing about Kelley and Meka’s work is that they were able to make such dramatic progress without developing a new approach to arithmetic progressions. Though they brought new insights and established new connections to previous work, they did not create new machinery.  

“It just seemed completely intractable to push those techniques through,” Sisask says, “until this paper by Kelley and Meka landed in my inbox.” He and Bloom, who had previously broken the logarithmic barrier, “spent a while digesting the paper and talking about it until we understood it in our own language,” he says.  

Mathematicians and computer scientists tend to use some different notation and terminology, but Sisask, Bloom and other experts in the field quickly recognized the work as solid. After digesting the arguments, Sisask and Bloom wrote an explanation of the work, with some subtle technical improvements, geared toward other researchers in combinatorics. Several months later, the team coaxed the upper limit down a tiny bit more, getting a new bound of 1/e^{(log(N))^1/9}. 

Combinatorics researchers are still trying to figure out how low they can go. Will they be able to push the upper limit all the way down to the best known lower limit, or will there always be a little gap where our knowledge is incomplete? Kelley and Meka are using the tools they honed on arithmetic progressions to continue work on problems in complexity theory and other areas of theoretical computer science. 

When I asked Meka how two computer scientists made such a big advance on a mathematics problem that had stumped combinatorics experts for years, he said he isn’t sure. He thinks maybe their edge came from being fresh to the challenge.  

“The problem has been around for a long time and progress seemed pretty stuck,” he says. In fact, after he and Kelley were well on their way to publishing, Kelley says he ran across a blog post from 2011 that outlined exactly why mathematicians were pessimistic about the very approach that the two had eventually used.  

“People thought that these techniques couldn’t push beyond existing barriers,” Meka says, “but maybe we didn’t know that the barriers existed.”  

Earth’s oldest, knotted and scarred pine trees are a boon for forest life. 

These old mountain pines (Pinus uncinata) offer food and shelter for lichens and insects not just because they’re old, but also because of what’s allowed them to grow so old in the first place, researchers report February 5 in the Proceedings of the National Academy of Sciences. The findings highlight the broader importance of big, old trees, and suggest threats to their survival from development, fire or climate change could deliver irreparable harm in certain ecosystems.

Old growth trees continue to decline around the world (SN: 6/18/18). In Europe, the remaining patches of forest with plentiful old trees constitute just 0.7 percent (or just under 3.5 million acres) of the continent’s forested area. This paper and others like it “are really good, because they show how important old growth is,” says Joseph Birch, an ecologist at Michigan State University in East Lansing who wasn’t involved with the research. This line of work serves as a reminder that we need to have a long-term perspective on old growth trees. “We need to be managing and conserving the forests that we have now, even if they’re younger, so that our descendants in a few hundred or even thousand years can have more old growth on the landscape,” Birch says.

While the pines’ old age, potentially hundreds of years old, was intriguing to plant physiologist Sergi Munné-Bosch and ecophysiologist Ot Pasques, both at the University of Barcelona, they have also been curious how aging and tree decay affect the broader forest ecosystem, with different life and decay stages providing differing habitat needs to plant, animal and lichen species.

Prior studies tended to look at how individual trees aged. So Munné-Bosch and Pasques decided up the ante. They studied young, adult and extremely old mountain pines in five different areas of the Spanish Pyrenees mountains. The duo calculated the trees’ ages based on tree trunk girth. (The two traits are correlated, eliminating the need to bore a sample out of the trunk to count tree rings). The team also weighed and measured needles, buds and shoots, analyzed the trees’ tissues for biochemicals linked to stress, decay and growth and noted age-related physical traits in the trees — such as exposed roots, fissured bark and lightning scars. Data on other species living in or on the trees were also recorded.

The results show that the oldest trees no longer spend a lot of energy on reproduction, ramping down the production of cones and buds, slowing their growth considerably and prioritizing stress tolerance and long-term durability. Ancient trees also allow parts of their bodies to die and decay alongside living sections. These are adaptations for staying alive hundreds of years, and they make the oldest trees knotted, scarred and full of large, dead sections, which are exploited by other forest life.

Ant colonies and plants like mountain houseleek (Sempervivum montanum) live in these dead and decaying sections. Trees with biochemical changes associated with decline and decay also tended to host more lichen, and the bigger, older trees had a higher diversity of lichen living on them. “Lichens look for very specific microhabitats for survival in high mountains,” Munné-Bosch says. Wolf lichen (Letharia vulpina), for instance, is rare in this part of Europe, and when the team encountered it, it was growing mostly on ancient pines.

Younger pines, which don’t have the unique physical and physiological features of ancient trees, can’t support forest life like ancient trees do. This makes ancient trees’ ecological role “irreplaceable,” Munné-Bosch says.

“For a lot of people who work with old trees, this is something that we intuitively knew. But it hadn’t necessarily been presented in this way and with such a compelling body of evidence to support it,” Birch says. 

These results are only for a single tree species, he notes. In giant sequoias, which live thousands of years, aging doesn’t cause the tree to contort in shape as dramatically as the stunted mountain pines that grow at high elevations, so ancient sequoias’ influence on biodiversity might look different. 

Branching out to study other tree species is the team’s next step, Munné-Bosch says.

It’s June 2023 and Victor has been spending most of his days at what he calls his “second home,” on East 126th Street, between Park and Lexington avenues, in East Harlem. A dozen or so men congregate outside, some sifting through belongings in a plastic bag or texting on their phone, others sitting on folding chairs or stools, playing cards, smoking, talking or just watching passersby. As an unhoused person in New York City, Victor says OnPoint NYC, a nonprofit organization that opened two overdose prevention centers in November 2021, provides him a “sense of community” he can’t get elsewhere.

Inside, Victor, who provided only his first name when I talked to him last June, will go through reception and into a back room. He’ll fill out a form that provides the information OnPoint needs to make sure he doesn’t die. The form asks for his name and time of arrival, what drug he’ll be consuming and how he’ll consume it. From a list that includes meth, marijuana, cocaine, crack, benzos, fentanyl, speedball and many more, he checks heroin, which he’ll inject. At the bottom, the form asks: “If you weren’t using here now, where would you have gone to use?” Options include the street, sidewalk, between cars, under a bridge, a park, a public restroom, a subway station, your own place (Victor doesn’t have one), a friend’s place or “other.” And it asks if he’d be using alone.

“Yes” is a common answer to that last question. That’s why OnPoint NYC exists. Its two locations, the one in East Harlem and one in the Washington Heights neighborhood, are the only officially sanctioned overdose prevention centers, or OPCs, operating in the United States. People bring drugs they’ve obtained elsewhere and use them under the supervision of trained staff who can provide sterile supplies for drug use and can respond to overdoses.

The approach remains highly controversial in the United States, with critics pointing out that the sites are sanctioning, if not encouraging, illegal drug use. What’s more, critics are concerned that OPCs increase crime, local drug use and public nuisance in the area. This opposition is just one of the challenges alongside many legal, social, financial and logistical barriers for an OPC trying to open and remain open.

“I understand what it sounds like, right? You’re gonna allow people to use drugs on your site,” says Sam Rivera, executive director of OnPoint NYC. “When people question whether it’s good or it gets people well, showing them is what gives them the answer. The answer is yes, of course it does.”

The United States had more than 106,000 drug overdose deaths in 2021, the most recent year for which complete data are available. That’s more per capita than other high-income countries with available data. The vast majority of those deaths involve opioids, including prescription opioid medications and heroin, but predominantly synthetic opioids such as fentanyl. Annual deaths from opioid overdoses have more than doubled since 2015.

“We obviously need to figure out what alternative interventions we can provide to people to prevent them from dying,” says Nora Volkow, director of the National Institute on Drug Abuse in Bethesda, Md. “It’s crucial.”

After Congress directed that institute along with the Centers for Disease Control and Prevention to conduct a report in 2021 on the potential public health impact of OPCs, the agencies’ findings noted “the consistent observation that initial objections to OPCs from local stakeholders tend to disappear following their implementation.”

OPCs have existed around the world for decades. Research has shown that they meet many of their primary goals: reducing overdose deaths, health care costs, the use of emergency services, emergency room visits, hospital stays, public drug use, infectious disease from nonsterile needles, and drug-related litter, such as used syringes. The sites also let people test their drugs to find out what they actually include. Many sites provide additional services aimed at improving overall health — infectious disease screening or testing, wound care, substance use treatment referrals and other programs that meet health care or social needs.

There’s been growing interest in the United States as well. A 2017 study estimated that an OPC in Baltimore that would cost $1.8 million a year to run would save the city $7.8 million a year in health care costs, but Maryland’s legislature has yet to authorize one. A center operated in San Francisco for nearly 11 months in 2022 before shutting down due to political backlash. Last year, the state of Minnesota and the city council of Somerville, Mass., each set aside money for OPCs. Additional sites have been proposed or are under consideration in Seattle, Denver, Philadelphia and elsewhere.

OnPoint has become a model for proposed sites across the United States. Researchers are analyzing its data, alongside data from other countries, to assess how OPCs might fare in a country without universal access to health care, with limited social safety nets, and with more drug use and overdose deaths.

In April 2023, the National Institutes of Health awarded the first portion of a grant, expected to total more than $5 million over four years, to researchers who will assess the effectiveness and costs of OPCs based on data from OnPoint and another site approved by the Rhode Island legislature and slated to open this year. That data could help shape how future centers operate and what services they offer, as well as how the nation approaches drug use more generally.

For Victor, the benefits of OnPoint go far beyond the immediate services provided. “It’s them treating you and looking at you as a person, because most people, most places you go, once you tell them you’re doing drugs, they have an idea of who you are already, a stigma,” he says.

Fostering community can be key to recovery, Volkow says: “That building of trust and a sense of acceptance and belonging is really the first step that can make a person want to go to treatment.”

For Rivera, the experience at the center is, “for lack of a better term, a lovefest.” Though he says his staff never initiates conversations about detox, treatment, rehab or recovery, they nevertheless have those conversations every day with people who come to the center.

What is harm reduction?

The first OPC opened in Bern, Switzerland, in 1986, and today there are more than 140 legally-sanctioned OPCs in more than a dozen countries, including Australia, Canada, Mexico and across Europe. Since Canada opened North America’s first OPC, Insite, in Vancouver in 2003, it’s added dozens more sites around the country, plus more “pop-up” mobile spots run out of tents or campers. OPCs are also known by other names, such as supervised injection sites, drug consumption facilities and safe consumption sites. But regardless of what you call them, the philosophy is the same: harm reduction.

Harm reduction “focuses on improving the health and reducing the negative health outcomes for individuals,” says Elizabeth Samuels, an emergency and addiction medicine physician at UCLA. “At its most basic level, it’s treating people with respect, dignity and autonomy,” and giving them info and tools “to keep themselves and their loved ones safe.” Laws requiring seat belt use in cars are harm reduction tactics. So are adding filters on cigarettes and distributing condoms to prevent pregnancy and the spread of sexually transmitted infections.

Samuels says there’s plenty of evidence that harm reduction strategies work to reduce drug-related problems. Yet in the United States, such interventions — providing safe, sterile drug consumption equipment, for example — are often stigmatized or criminalized. The current approach of punishing people who use drugs is a carry-over from the failed “war on drugs,” she says, “but it remains pervasive in the American psyche and in some portions of the general population.” We know addiction is a disease, not a moral issue, she says. “Pushing people underground and making them feel shame,” she adds, increases risky drug-related behaviors, such as sharing needles, which can transmit bloodborne diseases like HIV and hepatitis C.

Barriers to OPCs in the United States are financial (for example, who is going to fund them?), logistical (where will they be located?) and social (will communities accept them?). But the biggest hurdle has been legal. In a section often called the “crack house statute,” the Anti-Drug Abuse Act of 1986 makes it a felony to “knowingly open, lease, rent, use or maintain any place, whether permanently or temporarily, for the purpose of manufacturing, distributing or using any controlled substance.” Crack, a form of cocaine that is nearly always smoked, has come with harsher penalties than other forms of the drug. Cocaine in crack form has historically been perceived as more prevalent in Black communities, which has contributed to racial injustices.

A nonprofit called Safehouse tested this law in 2019, attempting to open an OPC in Philadelphia. The effort kicked off a court battle, and in 2021, the Third Circuit Court of Appeals ruled that the proposed OPC would violate the statute. Safehouse continues to explore its legal options.

Meanwhile, harm reduction advocates in New York were growing desperate as people died from overdoses — more than 2,000 in New York City during 2020 alone. New York Harm Reduction Educators in East Harlem and the Washington Heights Corner Project, both harm reduction social services organizations, had been running syringe exchange programs and offering related services in the city since the early 1990s. Representatives from these groups had done the logistical groundwork to open an OPC and had the support of city hall. A 2018 feasibility study conducted by the city’s health department and funded by the New York City Council suggested that opening four OPCs in New York City could prevent up to 130 deaths a year and save $7 million annually in public health care costs.

In the early days of 2021, the New York groups had a choice to make. The Safehouse ruling, from a different federal appellate court than the one overseeing New York, showed the potential legal risks of opening an OPC. But after President Joe Biden took office and listed “enhancing evidence-based harm reduction efforts” as a drug policy priority, the groups decided to move forward, merged into OnPoint NYC and opened two new sites.

“Our people are dying, and we know we have the medicine, the apparatus, everything we need to keep people alive, and they don’t have to die,” says Rivera, who was named as one of Time magazine’s most influential people of 2023.

While most of OnPoint’s extra services receive funding through city and federal grants, the overdose prevention and drug supplies services are funded through private dollars, a mixture of individuals, nonprofit organizations and foundations.

So far, OnPoint hasn’t been challenged in court, but the Anti-Drug Abuse Act statute remains a major deterrent to building more centers, Samuels says. Lack of public funding and community resistance are also barriers. The vast number of people dying has changed the climate somewhat, she says. More people are seeking all the “evidence-based tools in our toolbox to prevent any further loss of life.”

What does existing OPC research show?

Along the top of the back wall in the safe consumption area at OnPoint in East Harlem, where Victor uses his heroin, blue painted letters announce: “THIS SITE SAVES LIVES.” And below it in Spanish, “ESTE SITIO SALVA VIDAS.” Below are two defibrillators, each with plushies on top, including a Pokémon Psyduck, a gray puppy and even one shaped like a grinning bottle of naloxone, a medication used to reverse opioid overdoses. Two crash carts are ready to go if the staff notice someone slumped over, becoming discolored or otherwise showing potential signs of an overdose, which happens about three to five times a week, says Alsane Mezon, a harm reduction specialist at OnPoint.

Existing research on OPCs, which comes primarily from Insite in Vancouver and the Uniting Medically Supervised Injection Centre in Sydney, suggests the sites do save lives. The first major systematic review, published in 2014 in Drug and Alcohol Dependence, included a study looking at overdose deaths in Vancouver before and after Insite opened in September 2003. Nearly 90 overdose deaths occurred within 500 meters of the site in the period from January 1, 2001 to December 31, 2005, with the fatal overdose rate declining by 35 percent after the opening. That’s compared with a 9 percent reduction over the same time period in the rest of Vancouver.

In a study of the area around the OPC in Sydney, the average monthly number of ambulance calls for opioid-related overdoses in the hours the center was open, which numbered in the hundreds, decreased by 80 percent after its opening. The decrease was more dramatic than what was seen in the rest of the state of New South Wales. None of the studies included in the 2014 review or a more recent one from 2021 documented any death from overdose inside an OPC.

Despite concerns from critics, the reviews also found no increase in crime, drug trafficking or drug use–related public nuisance associated with the OPCs but did document reductions in syringe litter and public drug use. And when it comes to concerns about the sites encouraging drug use, one study from the Vancouver site showed no increase in relapse rates or the overall number of people in the area who used drugs, nor a drop in those starting methadone therapy.

Neither review linked OPCs to a decline in the number of people who injected drugs, but four studies of the Vancouver site and one of the Sydney site suggested an association between visiting OPCs and the likelihood of being referred to addiction treatment or entering a detox program. The 2021 review, published in the American Journal of Preventive Medicine, found frequent use of OPCs increased the rate of accessing treatment by 1.4 to 1.7 times compared with those who used drugs but visited OPCs less frequently or not at all.

A study of the Vancouver site calculated that, after accounting for the cost of running the site, it saved 14 million Canadian dollars in medical costs over a decade, including prevention of 1,191 new HIV and 54 new hepatitis C infections.

Early results from OnPoint appear consistent with previous findings. OnPoint staff and NYC health department employees reported in JAMA Network Open that during OnPoint’s first two months of operation, 613 people used services a total of nearly 6,000 times across both sites, most often for injecting heroin or fentanyl. As seen in Vancouver and Sydney, most visitors were male, and just over a third were unhoused. Center staff responded 125 times to an overdose or near-overdose, with EMS being called five times and three people transported to the emergency department. OnPoint has not recorded any overdose deaths within its walls since it opened.

Three-quarters of people who went to OnPoint said they would have used drugs in a public place. About half of those who went accessed other services there: picking up naloxone to have on hand, going to counseling, receiving medical care or a holistic service such as acupuncture.

Until OnPoint opened, the only peer-reviewed research on OPCs in the United States came from an underground site that opened in 2014 in an unnamed location. In a research letter reported in 2020 in the New England Journal of Medicine, Alex Kral, a behavioral health epidemiologist based in the San Francisco Bay Area with the nonprofit research institute RTI International, and colleagues evaluated the site’s first five years of operation. Out of 10,514 drug injections, 33 opioid-related overdoses occurred on-site and all were reversed with naloxone, with no deaths or transfers to medical facilities.

A separate study by Kral and colleagues, reported in Drug and Alcohol Dependence in 2021, looked at police reports of incidents in the area around the underground site and at two comparison sites without OPCs for five years before and five years after the site’s opening. Drug incidents had been declining around the OPC before opening and continued to decline afterward, suggesting the site had no negative impact. The analysis also found a decrease, rather than an increase, in crime around the OPC site.

Kral, who is not aware of other underground sites in the United States, also studied the OPC that opened in San Francisco in January 2022 and remained open through December of that year. In addition to safe consumption booths, the site offered on-site buprenorphine treatment (to treat opioid use disorder), legal services and even recreational activities such as karaoke competitions. That site reversed 333 opioid overdoses, about one per day it was open. Kral’s team analyzed data on general nuisance and drug-related nuisance within a 500-meter radius around the OPC and around a similar comparison area elsewhere in San Francisco. The analysis suggested, contrary to claims often made by critics, a reduction in nuisance overall, and no increase in drug-related nuisance or homelessness.

Similarly, a separate group of researchers, unaffiliated with OnPoint NYC, recently reported data showing no significant change in violent or property crimes, 911 calls for crime or medical incidents or 311 calls related to drug use in the immediate six-block areas around the OnPoint OPCs.

The small amount of U.S. research has already started to inform policy, Kral says, pointing to the Rhode Island and Minnesota legislatures’ decisions to authorize the opening of OPCs. “We are seeing politicians take what can be a political risk to do this, and I think our data is part of the reason for that,” he says.

What will the new U.S. study test?

Still, the existing research isn’t without limitations. All of the studies are observational, meaning they can show correlations but cannot attribute benefits directly to the OPCs. Many other factors might play a role in local crime rates, medical service utilization, homelessness, infectious disease spread and so on.

OPCs are also far from homogenous. Though the systematic reviews found that OPCs reduce overdose deaths locally and do not come with increases in local drug use or crime, the 2021 review noted that not much research exists in “resource-poor and politically diverse settings.” Drug use and structural factors, such as law enforcement practices and stigma around drug use, differ across different regions. Assessments of the value of the OPC-linked social services, which themselves vary widely, are also limited.

All this leaves a big question open: Can OPCs dramatically reduce harm in the United States, a country with a lot of drug use and among the highest overdose mortality rates in the world?

The new study funded by the National Institutes of Health through the National Institute on Drug Abuse could help answer that question by studying two OPCs over five years. Researchers from New York University will look at both OnPoint sites, and Brown University researchers will focus on the OPC that is set to open in Providence later this year.

That Providence site, in the process of hiring a medical director and finalizing the location, will be funded by $3.25 million allocated from lawsuit settlements between the state and opioid manufacturers, distributors and pharmacies, as well as with money from private foundations and donors, says Annajane Yolken, director of strategy at Project Weber/RENEW, a nonprofit that is helping establish the site. None of the NIH research money will go toward the center’s operating expenses.

The study, part of the NIH harm reduction research network, will look at four outcome types: the impact on people who use the facilities, based on surveys and health records; effects on neighborhoods, including crime, public attitudes and economics; qualitative findings from interviews with OPC staff and clients; and the costs, of running the site versus health care savings, for example.

“We are first and foremost scientists — we’re not advocates — so our task is to bring the highest level of scientific rigor to these questions, and we’re hoping that the science can inform policy,” says Magdalena Cerda, the NYU epidemiologist leading the OnPoint portion of the study.

“There are some unique aspects of the U.S. context that justify the need for this kind of study,” says Brandon Marshall, the Brown University epidemiologist leading the Providence portion. Most countries with OPCs have universal health care, and OPCs are funded through that system. The United States doesn’t have that structure, which often means Americans engage with health care differently than people in other countries. “Here, health care provided at an OPC might be the first time someone is experiencing compassionate, low-threshold and free health care,” Marshall says.

Barriers to health care, particularly for chronic pain or mental health conditions, are likely one reason drug use is worse in the United States than in other countries, Kral says. Volkow also points to the “tremendous social disparities” in the United States.

“Health care provided at an OPC might be the first time someone is experiencing compassionate, low-threshold and free health care.”

Brandon Marshall

Social inequities and the lack of a social safety net in the United States may influence how big a difference OPCs can make in reducing overdose deaths, Samuels adds. There’s also the punitive treatment of drug use, including its criminalization, and an aversion to harm reduction strategies compared with other countries with OPCs, Marshall says. He adds that addressing these issues is additionally challenging because of the racist roots of many U.S. drug policies.

What works in Canada and Australia may turn out not to work in the United States, and success may vary across U.S. locations too. One key strength of the two-site study is how much New York City and Providence differ from each other.

“One of the real values of our study is the fact that it leverages two very different contexts, a very urban, dense context of New York City and then the less urban, more suburban Providence,” Cerda says. “Being able to compare those contexts will hopefully give us some more generalizable insights.”

Another big difference will be the services provided. “If you’re going to open an overdose prevention center, then you have to think about all of these wraparound services,” Rivera says. Once people are there, they can have a decent meal, take a nap, meet with a case manager and more.

Cerda refers to OnPoint as the “Cadillac” of OPCs, because it offers so many wraparound services. The plan for the Providence site does not include as many of those services, but the site will be located alongside a treatment program. That could be a benefit for access to treatment, or it might make people more uncomfortable going there.

“We know that the more people use an OPC, the more likely they are to enter into some kind of addiction treatment program broadly,” Marshall says, “but we don’t really know at a more granular level what that looks like.”

A need to pair data with stories

When I met Rivera at his office at OnPoint in June, he was wearing torn gray jeans and a plain gray T-shirt that said in bold white letters: “HEALTH JUSTICE FOR ALL.” He’s a physically large presence, and with his thick, tattooed arms and hands adorned with silver and turquoise jewelry, he might seem intimidating if not for his kind eyes and inviting demeanor.

Hanging on the wall behind the desk in his office, cluttered with knickknacks both practical and decorative, is a plastic plaque commemorating the documentary Clean Needles Save Lives. The 1991 film tells the story of the illegal needle exchange program, run by the activist group AIDS Coalition to Unleash Power, or ACT UP, that was established in response to the AIDS epidemic.

Rivera defines “health justice for all” as access to health care without barriers — “an opportunity for someone who’s actively using drugs to use safely and have supplies that are clean and healthy. That’s health care,” he says. “Quite frankly, many drug users don’t have access to health care in the way they need it and deserve it.”

No one expects OPCs to solve the entire drug problem in the United States. For example, sites typically do not allow pregnant individuals or those under 18 to use their services, and women may not feel as welcome at many sites given that the people using OPCs are predominantly male, many with a history of incarceration.

Even for those who do visit the sites, there are barriers. Some people have difficulty injecting themselves, but most sites do not allow someone to help another person inject. Another potential barrier is a lack of smoke rooms — OnPoint has these but many OPCs do not — which is an equity issue because it excludes people who use drugs in this way.

Despite the limitations, Samuels says, OPCs have shown they help people and they save lives. “That’s meaningful in itself,” she says, “and part of a comprehensive, multimodal strategy to address the overdose crisis.”

Jonathan Giftos, an addiction medicine physician and the former assistant commissioner of the NYC Bureau of Alcohol and Drug Use Prevention, Care and Treatment, similarly regards OPCs as one piece of a bigger picture. While the city does not provide funding for OnPoint’s OPC services, the bureau where Giftos worked serves as the city’s liaison with the center, which does receive city funds for some of its extra services.

“No one service solves all problems, and they don’t necessarily replace or supplant other important things, like prevention or treatment or recovery spaces,” says Giftos, now chief of ambulatory care at NYC Health + Hospitals/Woodhull. “As we evaluate their impact, it’s important that we interpret the results through that lens and not think that because they didn’t solve every single problem facing a community, that they’re not effective.”

In his qualitative research from the underground site, Kral regularly heard that people using the site didn’t have friends and felt disconnected from the community. OPCs allow vulnerable people who have been stigmatized by society and burdened by shame to “actually be themselves for a moment” and to develop relationships that encourage them to make decisions “about the kinds of things they want to change in their life,” he says. These centers offer possibilities that can’t be measured in overdose or infectious disease rates.

“No one service solves all problems, and they don’t necessarily replace or supplant other important things.”

Jonathan Giftos

“The way I have been able to really help people is with empathy, respect and love,” says Mezon, the OnPoint harm reduction specialist. She is a medical assistant, but she says her personal interactions with people at the center are just as important as her clinical tasks. “When I come in, I tell them, ‘First you’re human. We’re going to show you respect,’ and that really changes the narrative.” Mezon says people come to the OPC from as far away as Long Island, Rochester, N.Y., and New Jersey not only because they can get a shower and test their drugs for fentanyl and other substances, but also because they know they will be treated with compassion.

She speaks about her work as a calling. “I have to walk this dark forest every day to find these beautiful flowers that get lost,” she says. “I’m just really grateful to have all walks of life here. This situation does not discriminate, so I’m here to help…. All the things that they’re not getting out there, we’re trying to give them in here.”

Marshall says a lot of work needs to be done to destigmatize addiction and emphasize the humanity of people affected by the overdose crisis. He believes that data and scientific research need to be paired “with the human perspective.”

Edward Krumpotich agrees. A drug policy consultant based in Grand Rapids, Minn., Krumpotich spent a lifetime battling addiction himself and lost his brother to a heroin overdose. He has also helped write half a dozen harm reduction bills in three states, including the 2023 legislation in Minnesota that authorized funding for an OPC.

“Many times, we get stuck in certain statistics. That doesn’t tell the whole tale of how this crisis is happening,” he says. “I think what it’s going to take is when community members realize that their next-door neighbor or their family member is somebody who suffers with this disease. I think when people realize that people like myself, who have been to 30-plus treatments, now write nation-leading law, it can happen to anybody.”

Marshall says personal narratives can change people’s hearts and minds. “Some of the strongest voices are people with lived experience who can really humanize this issue and explain how the crisis has personally affected them,” he says, “and how things like harm reduction enabled them to live happy, healthy lives.”

Migratory species don’t travel with a passport, but they cross borders all the time. This makes the animals’ conservation a uniquely challenging, international effort.

That effort needs a lot of work, researchers argue in the first-ever “State of the World’s Migratory Species” report published February 12 by the United Nations Environment Programme.

The report is the most comprehensive tally of the over 1,000 species protected under an international treaty called the Convention on the Conservation of Migratory Species of Wild Animals, or CMS. Nearly half of CMS species are experiencing population declines. Of those, fishes are faring the worst: 97 percent, roughly 56 species, are facing extinction. That includes species such as devil rays (Mobula mobular) and scalloped hammerheads (Sphyrna lewini).

“It’s that real decline in fish species that … is keeping me up at night,” said Kelly Malsch of UNEP’s World Conservation Monitoring Centre at a February 8 news conference.

The goal of the report is to guide priorities for CMS COP14, a meeting of global conservation leaders starting February 12 in Samarkand, Uzbekistan, to create new strategies for the protection of migratory species. This includes mammals, birds, reptiles, amphibians and insects. These groups overall are faring better than fishes, but the report still shows that 1 in 5 of all the species covered by the treaty is at risk of extinction. While much of the data in the report is alarming, success stories like the recovery of humpback whales may provide ideas for protection of other species, including fishes (SN: 11/18/19).

U.N. researchers reviewed data from the International Union for Conservation of Nature Red List of Threatened Species and found a 90 percent average decrease in the abundance of CMS-listed fishes since 1970. No other group of animals experienced an average decrease, let alone one this significant. The main culprits include bycatch (the accidental catching of fish), overfishing and pollution, the report notes.

The report goes beyond the species of every group already under the treaty’s protection and identifies almost 400 other species as vulnerable, including more than 200 fish species that are not yet protected — most of which have decreasing populations, like the zebra shark (Stegostoma tigrinum).

“When you drill down into it, very few fish species are actually protected,” says Richard Caddell, an expert in marine and environmental law and policy at Cardiff University in Wales, who was not a part of this report. Only a few, like those heralded for caviar, are better protected than the rest, mainly for their commercial value.  

Protecting migratory species on land across multiple countries is hard enough. But when it comes to animals in water, it’s a whole other beast. Most of the ocean is a mystery, and new environments are still being discovered, making conservation efforts harder (SN: 4/30/23).

And fish have another problem — they’re not sexy, Caddell says. Fish don’t draw conservation funding and international recognition the way gorillas and elephants and other charismatic megafauna do. “People think of a fish as being something that ends up on their plates,” he says.

This report might help to change that.

It recommends ways to protect migratory fish species from pollution and bycatch, like attaching LED lights to nets to deter certain fish. But it also keeps fishes in the spotlight, weaving the discussion of them throughout the report. By making their decline central to this report, delegates at CMS COP14 may take more notice, Caddell says.

“States not acting might not be [failing to protect fish species] out of malice or negligence, but out of sheer ignorance as to the true conservation status of a number of these animals, which is why a report like this is brilliant,” Caddell says.

More than 100 parties have signed and ratified the CMS since 1979. The United States is not one of those countries, but it has agreed to elements of the treaty focusing on marine mammals and sharks. But even for nations that have ratified the CMS, there’s no real legal penalties if they don’t follow the treaty. Instead, Caddell says reports like this new one remind those involved to do better.

“I think this report is a very, very welcome development,” Caddell says. “There’s an opportunity here to build a little bit of political momentum to try to think about fish in a different way. And to move away from that we’re just there to eat them.”