GEORGETOWN, TEXAS – Marijuana advocates head back to the Texas Capitol Wednesday of this week as a House committee prepares to discuss the first round of pot legislation. Lawmakers will hear testimony on three different proposals seeking to reduce the penalties for possessing small amounts of marijuana and an approach to legalize it outright.

As Texas seemingly draws closer to legalized marijuana possession and use each legislative session, what safety lessons are we learning from states who have legalized marijuana?

Julie Tappero sees job prospects lost every day at the temporary staffing company she owns, West Sound Workforce, located outside Seattle.

Since December 2012, when Washington state legalized recreational use of the drug, positive marijuana tests among her job applicants have more than tripled to about 15 percent. That means headaches for Tappero and many other companies struggling to maintain a drug-free workforce in drug-legal states.

These days, she has to bring in a larger pool of candidates and spend more time screening to rule out those who can’t pass or won’t take a drug test.

Workplaces in Washington and Colorado are adjusting to noticeable shifts, some cumbersome, others unexpectedly profitable, since marijuana became legal for adults 21 and older.

Courts continue to uphold a company’s right to maintain a drug-free workplace, and many businesses say they haven’t moved from that stance. Significant jumps in positive drug tests at some companies are resulting in firings, higher turnover and rejected applicants.

David Vine, of Swingle Lawn, Tree and Landscape Care in Denver, is getting a glimpse of the problem, and says it may get bigger once he starts seasonal hiring this spring.

“I’ve interviewed some people who didn’t know what was legal — 18-year-olds who thought it was OK for them to smoke [pot],” says Vine, the company’s human resources manager. “They’re not getting hired.” Because he has crews who “work 60 feet up in trees with chainsaws,” he says drug testing is not negotiable. “We’ve always done it and still do.”

“If you’re in the construction industry, marijuana use is not acceptable at any time, under any circumstance or condition,” said Rick Reubelt, Haselden Construction’s director of environmental health and safety in Colorado.

The company had such a tough time staffing required shifts that Reubelt said his team decided to abandon local job-recruitment efforts, pay current workers plenty of overtime wages, and look outside Colorado for drug-free employees.

Legal skirmishes also center on employee drug testing. Marijuana-using workers and lawyers representing the marijuana industry argue that a positive test showing low levels of THC does not meet the burden for proving impairment on the job.

Unlike alcohol, marijuana can remain in a user’s system for weeks. A heavy user who stops using can test positive for the next 60 days or more.

That’s precisely the problem for employers. An employee who drinks over the weekend can be sober and safe to work on Monday. In the event of a workplace incident, it is relatively easy to determine whether alcohol was a factor. Not so with marijuana. If an employee tests positive for low levels of THC, it is nearly impossible to rule out impairment as a cause.

Among those enjoying the business benefits of legalization is Jo McGuire, director of compliance and corporate training for Conspire!, a Colorado Springs testing company.

Business is up for Conspire! by 30 percent from a year ago. Many of the positive tests are coming from workers in transportation, manufacturing and construction jobs, “where there’s a clear zero tolerance policy and they know that,” says McGuire. “I had one guy, a sheet metal worker, come in with a THC level of 4,433. Remember, the cutoff threshold is usually 15.”

It appears that Washington and Colorado businesses are struggling under the newly legalized marijuana use laws, and at least in the short term, non-“legalized” states’ businesses may be the benefactors.