Hawaii workers testing positive for crystal meth and marijuana decreased in the third quarter, though more people tried to use synthetic urine to mask drug use in the workplace.

Diagnostic Laboratory Services Inc., which conducts drug tests for between 7,000 and 10,000 workers, said meth, or “ice,” use was down to 0.7 percent in the quarter from 0.9 percent in year-earlier period, according to a quarterly report released Tuesday. Marijuana use also dropped to 2.2 percent from 2.8 percent. Cocaine use remained flat at 0.3 percent, while positive opiate results fell slightly to 0.2 percent from 0.3 percent.

“What we’re seeing is probably not close to what the actual usage is out there,” said Carl Linden, DLS scientific director of toxicology. “We’re going with the assumptions that most people know that they will be drug-tested. Drugs are only detectable in the body for one to four days in the case of meth, so it’s a really narrow window to test for the drugs.”

However, positive results for synthetic urine were the highest since 2012, up to 1 percent from 0.8 percent in the third quarter of 2014.

“Though workforce ice usage in Hawaii has stabilized, we should not lose sight of the fact that we are still approximately four times above the mainland average among workers being tested,” Linden said.