When crime lab chemists handle evidence that contains illegal drugs, trace amounts of those drugs are inevitably released into the laboratory environment. When chemists scoop a bit of powder to test it, for instance, microscopic particles can become airborne and later settle on nearby surfaces. Particles can also be spread by touch.

To some degree, this is an unavoidable byproduct of the testing process, and it can result in detectable background levels of drugs in the lab.

Now, scientists at the National Institute of Standards and Technology (NIST) and the Maryland State Police Forensic Sciences Division have developed a protocol for measuring those levels and used their new protocol at three forensic chemistry labs. Their findings were published today in Forensic Chemistry.

Best practices recommend regular cleaning of surfaces to remove drug residues, but few labs currently monitor background levels. That might have to change as super-potent drugs like fentanyl, the synthetic opioid driving the nationwide overdose epidemic, become more common.

Forensic chemistry labs

Small amounts of fentanyl are often mixed into other drugs to boost their potency, and labs may have to increase the sensitivity of their instruments to detect those small amounts. If background levels are too high, that can potentially affect the test results reported by the lab.

"If I run a sample and it has fentanyl, I want to be sure that fentanyl came from the sample and not from background levels in my lab," said NIST research chemist Ed Sisco, the lead author of the study.

To measure those levels, the authors swabbed laboratory surfaces in the same way that airport security agents might swab a passenger's hands or luggage. At the airport, that swab would go into an instrument that tests for traces of explosive residue. In this study, the authors tested the swabs for traces of narcotics.

They swabbed laboratory benches, balances, telephones and door handle. They also swabbed outside the lab space, in evidence-receiving areas and office spaces. To ensure that the measurements reflected routine conditions at the lab, no unscheduled cleaning took place before testing.

To identify which drugs were present, the researchers used a technique called Direct Analysis in Real Time Mass Spectrometry (DART-MS). They then used Liquid Chromatography-Tandem Mass Spectrometry (LC/MS/MS) to measure how much of each drug was present. These instruments are more sensitive than the ones crime labs use for everyday drug casework.

"If you push your sensitivity enough, you will find narcotics on almost everything," and not just in chemistry labs, according to NIST research chemist and co-author Marcela Najarro. The authors cited a 2011 study that found detectable amounts of cocaine on 75% of shopping carts, ATMs and other frequently touched surfaces in public places.