As more states legalize marijuana, it's becoming a growing issue for the trucking industry. Recreational marijuana has been legal in Colorado since 2014, and drug tests indicate more drivers and job applicants are using the substance. Even as more trucking companies and commercial driver's license schools are telling candidates not to fill out applications if they're going to test positive, failure rates are still as high as 60 percent, said Greg Fulton, president of the Colorado Motor Carriers Assn. It's hurting the ability of some companies to grow, said Fulton. "It's just so much more prevalent. It's in cookies, muffins, bread, candy. More people are testing positive. People say they were at a party and just didn't know." Recreational marijuana is now legal in Alaska, California, Maine, Massachusetts, Nevada, Oregon, Washington and the District of Columbia. Medical marijuana is also legal in 29 states and the District of Columbia, and a 2016 survey from Gallup revealed that 13 percent of Americans said they use marijuana, up from only 7 percent in 2013. Still, trucking companies won't be changing their zero-tolerance policies anytime soon, in part because marijuana remains illegal under federal law and Department of Transportation regulation.