The iconic New York City skyline has reappeared as dangerous smog from Canada’s record-breaking wildfires clears over the Big Apple – but more than 50 million Americans remain under different air quality warning levels.
Health officials are still advising caution in a number of states to tackle pollution, including Pennsylvania, Connecticut, Rhode Island and Indiana.
A southerly wind continued to sweep smoke across the United States, with some areas including Ohio first hit this week on Friday morning.
The dissolving smoke comes after several major subways on the East Coast, from Boston to Washington, were engulfed in noxious fumes for several days, leading New York to briefly top the list of most polluted subways in the world.
WASHINGTON, DC: The Capitol is seen under hazy morning skies as air pollution in the city remains low

A noxious yellow haze enveloped New York on Wednesday (pictured) and lingered before dissipating mostly on Friday
Despite the easing of fog in some areas on Friday, the National Weather Service warns that states in the path of the southbound smoke are still at risk.
The forecaster warned that a low pressure system over the northeast in the coming days will “continue the flow of smoke” from the wildfires.
“Before the weekend begins, near-surface wildfire smoke associated with the Canadian fires is expected to continue to plague regions from the Great Lakes to the mid-Atlantic with reduced air quality,” said added the weather service.
By Saturday, the smog is expected to “relax” and the wind will “eventually shift to a more westerly direction.”
The smoke caused travel chaos on the East Coast throughout the week, with the FAA forced to ground flights from several major airports due to poor visibility.
The FAA announced no further delays due to smoke Friday morning, but disruptions are still expected in some areas.
School districts on the East Coast also took smog precautions, with school officials in Philadelphia and New York telling students to work from home on Friday.

Baltimore remains under air quality warning as smoke lingers in several states, pictured June 8, 2023

New York City was cleared of smoky haze as the sun rose over the subway on Friday, pictured June 9, 2023
The lingering effects of the smoke on several southern states have seen millions of people remain under orders to avoid outdoor exposure.
Mark Zondlo, an atmospheric chemist and air pollution expert at Princeton University, said the lingering problem was down to the composition of the smoke.
What makes it really unique — aside from the fact that the fires are huge on their own — is that the air stays very close to the ground,’ he told CNN.
“So instead of being transported and dispersing in the atmosphere or being in the layer 10,000 feet above us, it basically hugs the ground and therefore does not disperse.
“The weather pattern is such that it channels that plume of smoke, keeping it close to the ground, and it’s coming in for a target just for us.”

Residents of the Big Apple were ordered to shelter in place as hazy smog blanketed the city, pictured June 7, 2023
New York City Mayor Eric Adams said Thursday that while the smoke appears to have come and gone, it’s determined by several factors, including wind direction.
“The large plume we saw yesterday passed through the city and we expect a gradual improvement until early afternoon today,” he told a news conference.
“But a sea breeze this afternoon could blow the smoke back over the city.”
New York Governor Kathy Hochul added that while the Big Apple may have cleared up somewhat on Thursday morning, residents should remain cautious given the risks of ongoing high pollution levels.
“We could have some respite. But I don’t want people to let their guard down and get complacent about it, because we have to be prepared for the tide to turn,” she said.

New York’s Yankee Stadium pictured in foggy conditions before a game between the New York Yankees and the Chicago White Sox on June 7, 2023. The game was postponed due to poor air quality

Several major US cities have seen their Air Quality Index (pictured) score above 200, which is considered to be in the ‘very unhealthy’ range.
Air pollution levels have dropped significantly since their peak, which saw some states suffer from air quality so poor it was the equivalent of smoking an entire pack of cigarettes.
The smoke is made up of dangerous nanoparticles small enough to enter the bloodstream, and people have reported side effects including eye and throat irritation and breathing problems.
Determined by an AQI score – an internationally recognized pollution monitoring score – cities across the United States have been choked with some of the worst air on the planet.
The worst-hit area on Thursday was Windsor Township — about 70 miles west of Philadelphia — which scored a shocking AQI rating of 457. That eclipses the notoriously foul air of Delhi, India, with an index of 316.
According to tracking site IQ Air, on Friday morning New York City recorded an IQA score of 76. At its worst, the city topped 200 and listed itself as the most polluted city in the world.