EVERETT — A new study found fentanyl and methamphetamine are widely present on public transit in trace amounts, but “not necessarily” at a level that poses a health risk to the public, University of Washington researchers said Thursday.

Five transit agencies — Everett Transit, Sound Transit, Community Transit, King County Metro and TriMet — sponsored the first-of-its-kind study where researchers assessed the drug levels of air and surface samples from 11 buses and 19 train cars. Researchers sampled vehicles when riders most likely used drugs, based on past incident reports.

Of 78 air samples, researchers detected fentanyl in 20 samples and detected methamphetamine in all samples. And of 102 surface samples, researchers detected fentanyl in about half, and detected methamphetamine in nearly all samples.

“Just because we can measure it in the lab, does not necessarily mean that it’s at a level that poses a health risk to operators or riders,” Marissa Baker, who worked on the study as an occupational health researcher, told reporters Thursday. “There isn’t a lot of research as to what levels may cause health effects and after how much time, but at the level seen in this study, there is no clinical evidence of acute medical condition that would result from these passive exposures.”

Baker said no enforceable state or federal regulations exist for workplace exposure to methamphetamine or fentanyl. Health officials say riding public transit remains safe.

“We understand that the detection of fentanyl and methamphetamine in these spaces is concerning,” James Lewis, Snohomish County health officer, said in a press release. “The risk to the public from secondhand exposure is low, and we will continue to monitor as our knowledge base grows.”

Local transit agencies are working to improve ventilation, air filtration, cleaning and training practices to help reduce secondhand exposure. Community Transit is expanding its Transit Security Officer program to better enforce policies against smoking and drug use, and plans to upgrade transit air filters by the end of this month.

“We are going to undertake a deep cleaning protocol in consultation with the Snohomish County Public Health Department to establish a new baseline,” Ric Ilgenfritz, CEO of Community Transit, said. “With a clean fleet with new filters, we’ll then be able to monitor the rate of accumulation of these residues.”

All Everett Transit fixed-route buses have MERV 13 filters, the top recommendation from health officials. The agency has partnered with the Everett Police Department for “See Something, Say Something,” a campaign to empower people to speak up about drug use and other illegal activity on transit.

“Our buses provide an essential service to many residents who may not have other transportation options,” said Tom Hingson, director at Everett Transit. “Keeping our operators and riders safe is our number one priority.”

Sydney Jackson: 425-339-3430; sydney.jackson@heraldnet.com; Twitter: @_sydneyajackson.