The use of marijuana among Hawaii workers is the highest it’s been in three years, a new study shows.

The latest workplace drug report by Diagnostic Laboratory Services Inc. shows the number of employees testing positive for pakalolo rose to 2.9 percent year-over-year in the second quarter from 2.2 percent.

“Marijuana use is spiking. It’s also the highest rate of positives we’ve seen since second quarter 2013,” said Carl Linden, scientific director of toxicology at DLS, a medical testing laboratory with more than 600 employees in Hawaii, Saipan and Guam.

As Hawaii’s first medical cannabis dispensaries prepare to open this year, the trend is expected to continue.

“Unfortunately, we have seen an increase in the use of marijuana along with some other illegal substances, like crystal meth, over the past year,” said Michele Kauinui, director of human resources for SimplicityHR, owned by Altres, a payroll and HR outsourcing firm for more than 1,000 businesses in Hawaii. “With the legalization of medical marijuana in Hawaii, we have seen employees use that as a reason more often. Requests for drug-testing services for clients is increasing.”

Employers have the discretion to enforce a zero-tolerance drug policy, Kauinui said.

“The law is not saying that someone who has a medical marijuana card can test positive under a zero-tolerance substance abuse policy and still retain their employment,” she said.

The report also showed the use of certain opiates increased to 0.4 percent in the second quarter from 0.2 percent a year earlier, while the percentage of workers using methamphetamine fell to 0.8 percent from 0.9 percent. Both cocaine and synthetic urine use were flat at 0.4 percent and 0.9 percent, respectively, according to DLS, whose quarterly sample size typically includes between 7,000 and 10,000 drug tests.

State law prohibits testing for other prevalent prescription opiates such as Oxycodone and Vicodin, even though there’s been an “explosion” in public use, Linden said.

“We see more of that than codeine and morphine, but we can’t report it (to employers). There’s a legal limitation of what labs can test for,” he said. “They’re trying to legislatively change that, but those things take time. It’s frustrating for employers who are unable to test for all the opiates being used in this day and age. Lawmakers want expanded testing of opiates because obviously it’s a potential safety concern.”