Canadian Jason Dumelie spends most of his time deciphering and studying DNA sequences. But lately he's putting a lot of thought into something almost as complicated: his future.

As a Canadian working in the U.S. under NAFTA, he wonders if he could be collateral damage should president-elect Donald Trump follow through on one of his biggest promises.

"I'm quite concerned with a Donald Trump presidency; obviously it's not good for my personal status in the U.S. because he's said he'd rip up NAFTA," Dumelie said.

An estimated 30,000 to 40,000 Canadians work in the U.S. under the non-immigrant NAFTA Professional (TN) visa, which allows Canadian and Mexican citizens to work in the U.S.

The visa allows experts in certain fields — like economics and science — a fast track into the U.S., provided they have a job offer there.

"I've always known I'm here on a NAFTA treaty [exemption], so that if it gets ripped up, I've always been concerned, to an extent, that I may have to find a new job," Dumelie said.

'If we don't get a better deal, we will walk away'

During the campaign, Trump repeatedly attacked the free-trade agreement between the U.S., Canada and Mexico, going against Conservative orthodoxy but tapping into a rich vein of anger amongst a working class that feels left behind.

"If we don't get a better deal, we will walk away," Trump said in August during a major speech on economic policy in Detroit, where he highlighted the number of American manufacturing jobs lost since NAFTA was implemented in 1994.

During the first presidential debate in September, Trump went further: "NAFTA is the worst trade deal maybe ever signed anywhere, but certainly ever signed in this country."

Trump and Clinton spar over the trade deal her husband signed 1:27

At his office in Toronto, immigration lawyer Andrew Cumming has been hearing a lot from expats, asking about their visa situation in the U.S. and what options they might have under a Trump administration.

While their concern is justified, Cumming is advising clients not to be overly concerned.

"Even if NAFTA was torn up, I think a bilateral trade agreement would come in. So I think it's very unlikely that people on TN visas would be out of luck," Cumming said.

"When you talk about the loss of manufacturing jobs — the people going down under NAFTA on TN visas aren't manufacturing workers. They would be the engineers, or the computer science people behind building factories, creating jobs for Americans, so they actually play a vital role in increasing employment for Americans," Cumming said.

Trump attacking Mexico, not Canada

NYU business professor Robert Salomon said Trump likely isn't thinking of Canada when attacking NAFTA.

"I think Trump is more concerned about people coming and crossing the southern border into the United States, and staying and living and working here illegally. That is the bigger issue Trump is trying to attack," Salomon said.

Since his election, Trump's transition team has sought to soften the rhetoric around NAFTA, explaining in speeches to the business community that Trump isn't looking to rip up the deal, but instead to make it fairer.

NYU professor Robert Salomon says Trump is using the threat of ripping up NAFTA to deal with issues of trade and immigration with Mexico and likely isn't considering the impact on Canada. (Steven D'Souza/CBC News)

A draft memo from Trump's transition team, obtained by CNN, says on his first day of office, Trump would ask the U.S. Department of Commerce to study the impact of withdrawing from the agreement.

Salomon said while no one knows what Trump will do, his best guess is that NAFTA will be tweaked, not trashed.

"If he wants to rip it up, Canada will bear the consequences as well. But I hope that Trump sees the broader value of NAFTA and works to renegotiate elements of it, rather than rip it up entirely."

Concerns about reinterpretation

A bigger concern for Canadians still looking to move to the U.S., Cumming said, is if immigration officials take a more narrow approach to the agreement.

The job descriptions in the deal were written in the early 90s and don't reflect the current economy, he said. Officials could take a hardline approach to who gets in, limiting access.

"That's what we're most concerned about right now, on a day-to-day basis, is a re-interpretation of the existing laws in a more conservative sense," Cumming said.

Immigration lawyer Andrew Cumming says Canadians working in the U.S. shouldn't be too concerned about their work prospects under a Trump administration. He says the NAFTA section on immigration isn't overly contentious. (Ousama Farag/CBC News)

With a number of questions swirling ahead of Trump's presidency — from immigration to foreign policy to the environment — in typical Canadian fashion, Jason Dumelie said his visa concerns probably aren't high on the agenda.

"There are people concerned about much bigger things; it's definitely not why they're having protests here in New York City."

Given Trump's timeline for examining his options and the provisions in the agreement that state any member must give six months' written notice before withdrawing, Cumming said any potential changes to NAFTA are at least a year away.

That gives Canadians like Dumelie a bit of breathing room in the face of an uncertain future.