Fewer workers are testing positive for illegal drugs, continuing a sharp decline from 1988, according to medical testing company Quest Diagnostics. After reviewing more than 125 million urine tests administered from 1988 to 2012, Quest found 3.5% yielded positive results in 2012, compared with 13.6% in 1988. Methamphetamine rates fell with a government crackdown on illegal labs in 2005, but have begun to rise again, especially among workers in safety-sensitive industries like trucking and railroad operation. Quest also found that positive tests for amphetamines—including prescription drugs such as Adderall—have more than doubled since 2002. Other prescription medication use has become more common on the job, too. Over the past eight years, positive tests for painkillers Vicodin and OxyContin rose 172% and 71%, respectively. “Even when used under prescription, these drugs can have an impact on workplace safety,” said Barry Sample, Quest’s director of drug-testing technology. Some studies suggest 65% to 80% of positive tests for amphetamine and opiate use ultimately are disregarded because the user has a valid prescription, but employers still need to be more alert to the possibility these drugs are being abused, Dr. Sample said.