More than 70% of U.S. employers are dealing with the direct impact of prescription drug misuse in their workplaces, according to a new survey of more than 500 companies with 50 or more employees released by the National Safety Council, a nonprofit and nongovernmental agency promoting safety in the workplace. The survey, billed as the first of its kind in the U.S., also found that although a similar percentage of employers agree that prescription drug misuse is a disease that requires treatment, 65% feel it is a justifiable reason to fire an employee.

“Employers must understand that the most dangerously misused drug today may be sitting in employees’ medicine cabinets,” said Deborah Hersman, president of the National Safety Council. “Even when they are taken as prescribed, prescription drugs and opioids can impair workers and create hazards on the job.” The study included industrial companies, public and social services, professional services, retail and wholesale firms, and entertainment and agriculture industries. All respondents are human resources decision makers responsible for employee policies.

The percentage of workers testing positive for illicit drugs such as cocaine, amphetamines and methamphetamines among the U.S. workforce increased to the largest percentage in a decade in 2015, according to a workplace urine drug test of more than 9.5 million tests of urine samples, among other tests, by Quest Diagnostics, a company that provides national clinical laboratory tests on potential and/or current employees. The positivity rate for 9.5 million urine drug tests in the U.S. workforce increased to 4% in 2015 versus 3.9% the year before.

Drug poisonings, largely from opioid painkillers, in the last decade eclipsed car crashes as the leading cause of preventable death among adults. People addicted to drugs are buying them on the street, as they’re often cheap. People with a genuine need for pain medication leave drugs lying around where others have access to them, or they are simply sold. More often, they develop an addiction to pain medication after being prescribed drugs, said Leland McClure, medical science liaison of medical affairs at Quest Diagnostic. Quest found that opioid use is falling among workers.

In the most recent survey by the National Safety Council, 88% of the companies surveyed said they are interested in their insurer covering alternatives to pain relief treatment, and nearly 60% believe the insurance company will be responsive. But 30% of those employers will not act on that interest. And just one-fifth of employers said they feel “extremely prepared” to deal with prescription drug misuse in the workplace. But 70% of the employers surveyed said they would like to help employees who are struggling with prescription drug misuse.

People who work in fields where they’re at risk of injury and, therefore, are more likely to take pain medication, also surged in recent years, Quest found. They include medical workers who do heavy lifting, manufacturing, and retail workers, and factory and warehouse workers. Lifting and carrying material accounts for nearly one-third of all accidents, according to an analysis of more than 1.5 million workers compensation claims released last year by Travelers Companies Inc., an insurance company. The most frequent employee injury (strains and sprains) averaged 57 days off work.