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NEW YORK — Mikel Merino can smell and see the smoke from the Canadian wildfires that are making for hazy conditions across large parts of the U.S., including northern New Jersey, where he and Spain are set to face Argentina in the World Cup final Sunday.

Merino is trying not to focus on it.

It remains unclear how much, if at all, the smoke will affect the final. The World Health Organization forecast calls for an improvement to “moderate” air quality in East Rutherford, N.J.

“For a game that is as important as a World Cup final, you have to be able to shut out external factors as much as possible,” Merino said Friday. “Luckily, we are being careful with every detail thanks to the federation and the organizers of the World Cup.”

Spain practiced outside in hazardous conditions Thursday in East Hanover, N.J., alarming experts who thought the team should have held the session inside. Messages sent to FIFA and the Spanish Football Association asking whether that was considered or possible were not returned.

Air quality improved Friday, but the uncertainty lies in what will follow the up to 1.25 inches of rain expected to fall Saturday.

“Following that, it looks like there is another smoky air mass following in behind that system, but it’s not clear right now how much or how it might reach New York or New Jersey, when it comes to Sunday,” said Mark Parrington, senior scientist at the Copernicus Atmosphere Monitoring Service. “If the fire intensity really picks up again through (Saturday), it’s possible it puts more smoke into the atmosphere that then might quickly follow that rain event.”

Jonathan Belles, senior meteorologist for The Weather Channel app and weather.com, expects to have improved confidence in the forecast as game time gets closer.

“The question is whether smoke behind that (rain) system reaches ground level over northern New Jersey on Sunday and, if so, how concentrated it becomes,” Belles said. “Current forecast models range from little to no ground-level smoke to levels that could become more concerning for players and fans.”

Smoke from wildfires — which are burning more of North America as Earth warms — attacks nearly every system in the body, killing tens of thousands of people a year, numerous medical studies show.

It attacks the body immediately, spiking asthma cases with increased ambulance runs within hours. Smoke can trigger inflammation in different parts of the body, often attacking a person’s weakest points, which can then cascade into different effects of an immune system trying to fight a nasty irritant, doctors and scientists say.

There could be an impact on players’ performance even if the air conditions are moderate, according to UC San Diego professor of medicine Chantal Darquenne.

“It’s kind of a dose-dependent effect,” Darquenne said. “If it’s moderate, it’s going to be less of an effect, but it’s still going to be there, especially because they are doing vigorous exercise during these events.”

President Donald Trump was set to meet with FIFA President Gianni Infantino later Friday. Members of the administration, including Andrew Giuliani, the executive director of the White House FIFA Task Force, have been discussing the matter with soccer’s governing body and monitoring the wildfire situation, according to a White House official. The person was granted anonymity to confirm internal discussions.

Trump said he would impose new tariffs on Canada over the wildfire smoke but made no mention of the World Cup final.

“We are holding Canada responsible,” the president posted on his social media site. He added that the U.S. “is being unnecessarily invaded by filthy, polluted and unhealthy air, the quality of which is dangerous and totally unacceptable!”

About 80,000 fans are expected to attend the final at MetLife Stadium, the open-air stadium in the Meadowlands that is home to the NFL’s New York Giants and Jets.

“There’s the obvious sort of respiratory illness, cardiovascular issues, vulnerable people with asthma and things like this,” Parrington said. “Then for sure they’re going to feel the effects.”

During a rehearsal Thursday night at MetLife Stadium for Sunday’s halftime show, some members of the New York Philharmonic wore masks and some used outdoor-friendly instruments rather than the regular ones they play.

The haze has caused complaints across sports, with athletes critical about the decision to play in hazardous conditions. Before his New York Yankees played at home roughly 12 miles from the Meadowlands, manager Aaron Boone said he wasn’t hearing much about the smoke.

“Obviously they’re monitoring it to see if it gets any worse,” Boone said. “We’ll be communicating with our guys a lot. We’re able to test oxygen levels and things like that if guys are having trouble. So we’re paying attention to it, and we’ll take the guidance from the league and the weather and the smoke people.”

SNTV videographer Davidde Corran in East Hanover, N.J.; AP White House reporter Seung Min Kim and AP science writer Seth Borenstein in Washington; and AP sports writers Ron Blum in New York and Jim Vertuno in Austin, Texas, contributed.