CHICAGO - In a small, obscure government laboratory here, two self-described “nerds” are doing microscopic detective work, trying to determine the origins of the major narcotics shipments that U.S. agents intercept at the border.


Andrew Laurence, 33, and Shannon Ferguson, 32, are forensic palynologists who specialize in the identification of pollen grains. They can extract the particles from almost anything - drug packages, clothing, the air filters of impounded vehicles - and use that information to determine where an item might have traveled. Pollen grains stick to objects in abundance, and the precise combination of those particles creates what forensic palynologists call a “signal,” not unlike a fingerprint.


“The concept is pretty simple: all plants have a unique pollen grain,” said Laurence, who was hired by U.S. Customs and Border Protection in 2012 to establish the lab. “Each region is made up of different plants, or the same plants in different abundances - percentages on the landscape. So every part of the world is going to have a different pollen print.”


The palynologists’ work is of growing interest to the government at a time when record amounts of hard narcotics are flooding into the United States, often with little indication of their source or smuggling routes. Laurence and Ferguson are at the forefront of helping CBP determine, for example, whether shipments of deadly fentanyl seized at the border were made in Mexico or may have originated in China.


The technique also has applications for counterterrorism and other national security purposes, Laurence said, such as testing material found on explosives or criminal suspects. But Laurence said he couldn’t talk about that part of the job.


Laurence, who was recruited when he was a graduate student in archaeology at Texas A&M, said pollen grains can help CBP reconstruct the “travel history” of an item. Sometimes the sample reflects a broad geographic area, so the information is of limited use, but he says other items can be traced to a specific region or subregion.


Border Patrol agents also have been sending in soil samples from the field, allowing Laurence and Ferguson to build detailed pollen maps of the U.S.-Mexico border that might help identify where shipments crossed.


The information is not used for criminal prosecution, but it is valuable for “intelligence and investigative leads,” Laurence said. While investigators traditionally rely on interviews and informants to reveal trafficking patterns and the sources of narcotics, the CBP pollen lab can help substantiate that information or cast doubt on its veracity.


Neele Shepard, a chemist who has worked for 18 years in CBP’s narcotics lab identifying the chemical substances in seized drug loads, called the pollen analysis “an innovative new approach to collecting intelligence.”


“No one has ever been able to say ‘Hey, can you figure out where this brick came from?’,” she said.


Laurence said most of the samples he is asked to identify now are fentanyl. Wearing hazmat suites, respirator masks and other protective gear, he and Ferguson will sometimes dissolve an entire kilo brick in hydrofluoric acid and other chemicals, then separate out pollen grains using centrifuges.


Laurence said he is not authorized to discuss geographic trends in the fentanyl samples he is studying. But such information carries geopolitical significance at a time when the United States has been touting drug enforcement cooperation with China despite the deepening trade dispute between the countries.


The U.S. State Department also produces annual reports evaluating other nations’ counternarcotics efforts and their place in the illicit drug trade, assessments that can have implications for foreign aid, trade practices and cargo inspections.


After Laurence and Ferguson separate the pollen from other particulate matter on their samples, they inject dye to so they can view the granular structure under microscopes. Many of the grains are instantly familiar, especially tree species such as pine and oak that are wind-dispersed and scattered across the planet.


The researchers are looking for the percentages of those species in combination with more distinctive grains, particularly from plants with material that is not part of the ambient “pollen rain.”


The CBP in-house reference library has about 6,000 pollen types, and Laurence and Ferguson have access to another 30,000 samples nearby at the Field Museum of Natural History in downtown Chicago. Worldwide, there are about 380,000 types of pollen grain, Laurence said.


“We can always tell you the general environment, like the mesquite grasslands of Mexico, or the Great Basin of North America,” he said. “That’s probably the worst-case scenario, if that’s all we can say, where it’s these large environments, and there’s nothing unique about it.”


About 70% of what they find is composed of grain types in their reference library, but Laurence said there are many parts of the world that remain “black holes,” including parts of the Middle East, where there has been little mapping done.


When the CBP palynologists are not studying material from drug seizures, they often assist state and local authorities on hard-to-solve homicide investigations, including cold cases. Pollen molecules are extremely durable, so the grains remain intact on decades-old crime-scene evidence.


“Pollen itself is best described as a flying fossil,” Laurence said.


“Nature’s plastic,” Ferguson said. “You can’t get rid of it.”


In 2015, Laurence and Ferguson helped crack the high-profile Bella Bond murder case in Massachusetts, after the body of an unidentified toddler was found in Boston Harbor. State police sent Laurence garments and hair samples, and he was able to identify grains from two types of rare cedar trees that were in a Boston-area arboretum.


The discovery helped police narrow their search to a specific area of Boston, where they eventually arrested the child’s mother and her boyfriend, who lived near the arboretum. The boyfriend was convicted of second-degree murder, and the mother was convicted of being an accessory after the fact.


More recently, Laurence and Ferguson worked on a 37-year-old homicide case from Ohio, identifying pollen from the crime scene, and the victim was finally identified in combination with DNA testing.


A relatively abstruse area of research to begin with, palynology produces few graduates, and Laurence and Ferguson said most of the PhD candidates are immediately hired by oil companies. When they are spending tens of millions of dollars per day to drill deep under the ocean, the companies employ palynologists to test organic material from core samples to determine the geological strata, so engineers can direct crews to go deeper or pull back.


Ferguson joined Laurence in 2015 while she was completing her geology PhD at Louisiana State University. Ferguson said she liked the real-world application of forensic palynology.


“In geology, as a student, I was only focusing on stuff that happened thousands of years ago, which was interesting, too,” she said. “But this is more rewarding in a way, because it’s happening now. It can affect people’s lives. It can help people.”


The palynologists working for Exxon or Shell earn many times more than those in government labs like the CBP facility in Chicago. “Basically you have to be an idealist to work on the government side,” Laurence said. They are trying to recruit more palynologists to the CBP lab, as their current backlog of cases is 18 months to two years.


At Texas A&M, Laurence wrote his dissertation on “ancient starches,” analyzing material from earthen ovens to identify what grains were being cooked. His mentor, Vaughn Bryant, began promoting forensic palynology in the 1970s, after learning about its application in New Zealand and the United Kingdom.


Bryant often worked for the U.S. Department of Agriculture to identify the origins of honey samples, because importers will sometimes purchase cheap honey abroad and repackage it as a local product to boost the price.


Bryant said he got little traction promoting the law enforcement potential for forensic palynology until the Sept 11, 2001 terrorist attacks, then spent a decade analyzing samples for U.S. intelligence agencies.


“The next thing that happened was I got call from the Department of Homeland Security, and they said: ‘Do you think you could help us find out where this marijuana is coming from?’”


Bryant said he began working for DHS around 2006, and he was soon testing a range of narcotics seizure samples. But he already had a full-time job teaching and doing research. “I started talking to DHS and they said they’d be willing to fund a graduate student to learn how to do it. Andy was that student.”


“What I tell people is this: When forensic palynology works, it’s fantastic, but doesn’t work all the time,” Bryant said. “It’s just one tool to use to complement other forensic applications. It’s just one technique you can apply.”


Bryant, 78, said he has terminal cancer, but he has been heartened to see his protege, Laurence, continue the work.


“I felt like Moses, wandering the desert for 40 years,” he said, laughing. “It wasn’t until we had a major catastrophe until someone listened, and after that they couldn’t get enough info.”


“Federal agencies finally woke up to fact that this stuff can be very useful,” he said.