A Halifax man wonders if people realize that using a legal substance can affect their job prospects.

He's a recreational cannabis user, who was recently rejected for a job at the Halifax water utility after a pre-screening drug test.

“I don't do any illicit drugs, I'm a hard worker,” says Patrick Whalen.

When Whalen applied for a job as a labourer at Halifax Water, he says he didn't know he would be asked to undergo a drug test as part of the process.

“I thought, ‘OK, I'm not a frequent user, I use it once in a while,’” he said.

He applied for the job in April, got an interview May 3, and was offered the job that same day. Then he was told he would have to undergo a drug test as a condition of that employment.

He abstained for five days, then submitted his urine for testing.

The results came back positive for pot -- and Halifax Water withdrew their job offer.

“I got penalized, and did not receive the position, because I smoke legal cannabis,” Whalen said. “I didn't think I had anything to hide, because it's a legal substance.”

Halifax water says it has always pre-screened employment candidates for drugs -- but updated its policy May 1 to account for the legalization of recreational cannabis.

Halifax Water wouldn't speak to this specific case, but says job candidates are supposed to be made aware during the interview process if drug testing is required.

A spokesperson for the utility says the screening is a matter of safety.

“We're in water treatment plants, we're  around heavy moving equipment, trucks, vehicles, heavy duty electricity, all kinds of stuff,” said James Campbell of Halifax Water.“That's really, really dangerous and we want to make sure the folks that are working here are in their best possible condition.”

Jill Houlihan is an employment attorney who says it’s not prohibited for an employer to conduct drug testing on a prospective employee.

Houlihan says because cannabis stays in the body longer than alcohol - candidates who have to undergo pre-screening should think twice about using pot at all.

“The reality is if you are in the job market and you're applying for those types of jobs, you would be well advised to abstain from cannabis,” Houlihan said.

Whalensays that even though it’s legal, “it's restricted to a point where it's kind of silly.”

Whalen has found other work, but he wants others to know that how they use what's now a legal substance can affect them in ways they might not realize.

Another issue to add to this is the impending legalization of the sale of cannabis edibles and beverages in Canada this October. That means that's something else that candidates for employment will have to avoid if they have to undergo pre-screening tests.

With files from CTV Atlantic’s Heidi Petracek.