Wildfires are making the US smoggy again, reversing progress on cleaner air, study finds

WASHINGTON (AP) — For more than a decade, the United States dramatically reduced its national smog levels, but since 2015 smoke from increasingly larger wildfires is reversing that clean-up trend and making the air dirtier and deadlier, a new study finds.

Scientists say climate change deserves much, but not all, of the blame.

The national smog level dropped by 11% from 2003 to 2015 as strict federal regulations on power plants, cars and diesel engines kicked in. But since then, as wildfires have grown, the nation's average ground level ozone — which is smog — increased by 4%. That means if smoke increases at the current rate, smog will go back up to 2003 levels in 20 years, said study lead author Weizhi Deng, an atmospheric scientist at the University of Iowa.

Thursday's study in the journal Science also estimated an increase in deaths from ozone attacking lungs, using previously established epidemiology studies that compared death rates in clean and dirty air. They calculated an increase of 318 American deaths per year since 2013.

“For the last 20 years, by regulations, we keep decreasing the emissions" for human-caused smog-inducing chemicals, said study co-author Meng Zhou, a University of Iowa wildfire researcher. “However, because of wildfires, that is actually from natural hazards, all those kinds of effort were wiped out.”

The study was novel in the way it estimated the national smog level, compensating for how the U.S. Environmental Protection Agency has a limited number of smog monitors. Those cover only 2% of the nation, mostly in urban areas. So Deng and his colleagues used those observations — along with satellite, pollution and weather data and models — then used artificial intelligence to create a nationwide data set of ozone levels showing smog count at a resolution slightly higher than half a mile (1 kilometer).

EPA figures show the national ozone level since 2015 has vacillated around the same mark, going up and down a few percentage points, but Deng said, “by considering everywhere in the U.S., we actually found an increase in ozone starting from 2015.”

The method using artificial intelligence is solid because it starts with “massive and reliable datasets,” then uses computer models to fill in the gaps in a sensible way to make an “exceptional” high-resolution picture, said University of Delaware environment professor Cristina Archer, who wasn’t part of the study.

Megafire Action's research director and senior policy advisor Teresa Feo said “experts have long called for expanding the air pollution monitoring network to improve research on wildfire smoke exposure and provide the data needed to better protect public health.”

For decades, the U.S. tracked six traditional air pollutants, including smog and soot, which are tiny particles. This new study looked only at ozone, while a 2023 study by many of the same team looked at small particle pollution. They found the downward trend in soot levels had similarly reversed. Wildfire smoke increased particle pollution deaths by about 670 per year, the 2023 study found.

Fires don't produce ozone itself, but they release precursor chemicals that become smog when they interact with sunlight, scientists said.

“Higher daily ozone concentrations can increase asthma attacks, hospital admissions, and mortality,” said University of Washington public health and climate scientist Kristie Ebi. It's not quite as deadly as tiny particles, she said, but it's “still a very important pollutant, which is why it's regulated.”

During the heavy wildfire smoke seasons of 2022, 2023 and 2024, much of the fires were in Canada, but the smoke came south. In the U.S., 43 million people were exposed to smog levels that exceeded the current EPA safety standard, the study found.

And that standard isn't stringent enough, said Dr. Lynn Goldman, former dean of the George Washington University School of Public Health and a former EPA assistant administrator. In 2023, the Biden administration delayed plans to tighten those standards and then the Trump administration changed regulations that consider deaths and health impacts in smog and soot rules.

The biggest increase in ozone levels was in the Northern Rockies, which were near many of the fires, and in the Midwest, where the smoke traveled next, Deng said.

The average amount of U.S. land that wildfires burn each year is now 9% higher than it was from 2003 to 2014, according to the National Interagency Fire Center. But the wildfires in Canada have been particularly bad since 2022, scientists said. They pointed to 2023 when the skies were orange and people in the East were wearing face masks because of the Canadian smoke.

The amount of land burned in 2023 in Canada was not only a record but two times higher than the old record, said atmospheric scientist Brendan Rogers of the Woodwell Climate Research Center. Smoke from that year's Canadian fires killed 82,100 people globally — 33,000 in the United States — because of the particle pollution, a study in 2025 calculated.

Climate change, from the burning of coal, oil and gas, increased the intensity of Canada's 2023 fire season by at least 50% and doubled the chances of the drier, hotter weather conditions that were needed for the fire, a 2023 study found.

“Human-caused climate change is an important contributor, because it increases hot, dry fire-weather conditions in many regions,” said Lixu Jin, an atmospheric scientist at Rutgers who wasn't part of the study. “But wildfire emissions also depend on fuels, land management, ignitions, suppression, and year-to-year meteorology.”

Former EPA Administrator Gina McCarthy, who served in the Obama administration, said it was discouraging to see smog improvements being eroded.

Wildfires cause death and destruction, but the greatest danger may come from smoke and extreme heat increasing the ozone that harms people’s health, she argued.

“So the big question is," she said, “when are we going to stop the nonsense from this administration to burn more and more ‘beautiful’ fossil fuels?”

The Associated Press’ climate and environmental coverage receives financial support from multiple private foundations. AP is solely responsible for all content. Find AP’s standards for working with philanthropies, a list of supporters and funded coverage areas at AP.org.

FILE - A man runs in front of the sun rising over the lower Manhattan skyline in Jersey City, N.J., June 8, 2023. (AP Photo/Seth Wenig, File)

FILE - A woman steps away as the Sandy Fire approaches a neighborhood May 18, 2026, in Simi Valley, Calif. (AP Photo/Ethan Swope, File)

FILE - An air tanker drops fire retardant on the Sandy Fire on May 18, 2026, in Simi Valley, Calif. (AP Photo/Ethan Swope, File)

FILE - A firefighter works as the Sandy Fire approaches May 19, 2026, in Simi Valley, Calif. (AP Photo/Caroline Brehman, File)

FILE - Mayra Long looks from inside her home as the Sandy Fire approaches May 19, 2026, in Simi Valley, Calif. (AP Photo/Caroline Brehman, File)

FILE - Firefighters are silhouetted amid an operation to control the Sandy Fire, May 19, 2026, in Simi Valley, Calif. (AP Photo/Caroline Brehman, File)

ST. PETERSBURG, Russia (AP) — President Vladimir Putin said Thursday that Russia will strengthen its air defenses to counter recent Ukrainian drone attacks, which have reached deep inside his country and cast a cloud over his showcase economic forum in his hometown of St. Petersburg.

Speaking in response to a question from The Associated Press during a meeting with heads of international news agencies, Putin acknowledged the damage from Ukrainian drone attacks.

“To our regret, some of them break through,” Putin said of the drone strikes. “Russia has an air defense system, we need to improve it, strengthen it, and we will do that.”

The wide-ranging media session came on the sidelines of the St. Petersburg International Economic Forum, his annual showcase for investment. Hours before the forum opened Wednesday, a Ukrainian drone attack set ablaze an oil terminal in the city and also hit a nearby naval base.

Putin also said Russia is open for a compromise on Ukraine in line with understandings reached at his summit with U.S. President Donald Trump in Anchorage, Alaska, adding that Ukraine needs to accept them to make a deal to end the conflict, now in its fifth year.

Also on Thursday, Ukrainian President Volodymyr Zelenskyy proposed face-to-face negotiations in a public letter addressed directly to Putin. Zelenskyy acknowledged shifting U.S. priorities, saying it would be wrong to wait for the U.S. to return its attention to Ukraine while it is remains heavily focused on the Iran war.

In Washington, Trump said it “would be great” if Putin and Zelenskyy meet.

Kremlin spokesman Dmitry Peskov said Putin hadn’t seen the letter yet and repeated his statement that Zelenskyy could come to Moscow if he wants talks. Putin said last month he doesn’t exclude a meeting in s third country, but only when there is a deal to sign.

Putin dismissed the idea that European Union countries could mediate Russia-Ukraine peace talks because “mediation assumes neutrality. Where is the neutrality here?”

Any potential third-party mediators needed to be trusted by both sides, Putin said.

“How can Russia trust people who have been harping about the need to inflict a strategic defeat on Russia for years?” he said.

Commenting on Russia's use of its Oreshnik intermediate range ballistic missile, Putin said it was fired at targets that allowed it to test its capability and precision before using it against objectives closer to residential areas.

“We hit the area where it was convenient to see the results,” he said. “It was important for making a decision on the future on the full-format use of the Oreshnik on designated targets, including those in populated areas.”

Putin emphasized his push for control of the entire Donetsk region in eastern Ukraine, noting that Ukraine controls about 15% of its territory.

Putin declared that “patriotism and will of the Russian people” will ensure the achievement of goals that Moscow set in Ukraine.

“Russian troops are advancing along the entire line of contact,” he said.

Putin said he has accepted Trump’s compromise proposals from the Alaska summit, saying they could “serve as a basis of agreements between Russia and Ukraine and put an end to the conflict."

Moscow wants a comprehensive settlement, not a temporary truce, he said.

“There is no need to suspend the hostilities to start negotiations,” he said. “Naturally, the Ukrainian side would like us to suspend the advances made by Russian troops. But it would be better to end the war by agreeing to the compromises that were discussed in Anchorage.”

Asked about an AP investigation tracking 191 incidents across Europe, including sabotage, cyberattacks, attempted assassination and other activity that Western officials say are part of a Russian-masterminded campaign, Putin replied there was no detailed proof of Moscow's involvement.

“What are the specific facts? What has been proven?” he said, adding that the accusations showed that Europe was not ready to talk to Russia as an equal partner.

“This only shows that certain political figures in the West are trying to carry out aggressive plans against the Russian Federation,” he said.

Asked whether Russia could contribute to a settlement of the war in Iran, Putin responded that Moscow’s proposal to take enriched uranium from Iran for storage remains on the table. He noted Russia did so as part of the 2015 deal between Iran and world powers, "and we are ready to do it now.”

Putin, 73, who has held power in Russia for over a quarter-century, was asked if he planned to run for another term that would keep him in office until 2036, when he'll be 83. He laughed and said he’s “not even thinking about it.”

“Only God knows if any of us will be healthy enough ... to survive until tomorrow, the day after tomorrow, much less solve the problems we face and achieve the goals we set for ourselves,” he said.

In 2020, Putin ordered amendments to the Russian Constitution that essentially reset his term limits, keeping him in power.

Wednesday's drone attack hit the nearby Kronstadt naval base and an oil terminal, sending a plume of black smoke above Russia’s second-largest city — an embarrassing blow to Putin's efforts to cast the conflict as a distant event that doesn’t affect Russian daily life.

It also underscored Kyiv’s growing ability to hit deep inside Russia and showed the vulnerability of its cities. Scores of flights were delayed or diverted at St. Petersburg’s airport and authorities cut cellphone internet service to try to prevent drone attacks.

Putin had scaled down Russia’s annual Victory Day parade on May 9, fearing Ukrainian strikes. Days later, a massive drone attack on Moscow’s suburbs killed three and showed the capital’s vulnerability.

Peskov said Russia’s forces were carrying out “systematic” strikes on Kyiv. On Tuesday, Russia launched deadly attacks on Kyiv and other Ukrainian cities.

Putin has used the St. Petersburg forum, likened to the World Economic Forum in Davos, Switzerland, to showcase his country’s economic advances and encourage foreign investment. While Western officials and business leaders have stayed away after Putin sent troops into Ukraine in 2022, Russia has sought guests from elsewhere to underline its declared goal of promoting a “multipolar world.”

Saudi Arabia sent a large delegation this year, and the presidents of Uzbekistan and Tanzania and vice president of China also are present. A U.S. official, Rodney Mims Cook Jr., head of the U.S. Commission of Fine Arts, is attending for the first time in years.

Russia’s economic outlook has clouded as the initial boost from military spending has fizzled. The government raised taxes and increased domestic borrowing to keep its budget deficit under control.

Asked at the media session if Russia’s economy was struggling because of the military action, Putin paraphrased Mark Twain that “rumors of my death are highly exaggerated.”

He said the economy was growing but admitted that inflation was a concern.

“We’ve deliberately taken steps to cool the economy,” Putin said of Russia’s Central Bank putting the country’s key interest rate at 14.5%, which he called “a difficult decision.”

“You can say we’ve cooled off, or you can say we haven’t done everything yet, but these are deliberate steps. We don’t want inflation – hyperinflation -- to reach 60-80%, as it is some countries,” he said. “We’re fighting for the health of the Russian economy as a whole.”

The Associated Press News Director of Europe/Africa James Jordan, center, attends Russian President Vladimir Putin's meeting with representatives of international news agencies on the sidelines of the St. Petersburg International Economic Forum at the Constantine Palace in St. Petersburg, Russia, on Thursday, June 4, 2026. (AP Photo/Dmitri Lovetsky, Pool)

Russian President Vladimir Putin gestures during a meeting with representatives of international news agencies on the sidelines of the St. Petersburg International Economic Forum at the Constantine Palace in St. Petersburg, Russia, on Thursday, June 4, 2026. (Alexander Kazakov, Sputnik, Kremlin Pool Photo via AP)

Russian President Vladimir Putin, center, looks at President of Xinhua News Agency Fu Hua, right, while speaking to representatives of international news agencies as General Director of the Russian news agency TASS, Andrey Kondrashov, left, sits near on the sidelines of the St. Petersburg International Economic Forum at the Constantine Palace in St. Petersburg, Russia, on Thursday, June 4, 2026. (AP Photo/Dmitri Lovetsky, Pool)

Russian President Vladimir Putin, foreground answers to a question by The Associated Press News Director of Europe/Africa James Jordan, back to a camera as he meets with representatives of international news agencies on the sidelines of the St. Petersburg International Economic Forum at the Constantine Palace in St. Petersburg, Russia, on Thursday, June 4, 2026. (AP Photo/Dmitri Lovetsky, Pool)

Russian President Vladimir Putin, background third right, meets with representatives of international news agencies on the sidelines of the St. Petersburg International Economic Forum at the Constantine Palace in St. Petersburg, Russia, on Thursday, June 4, 2026. (AP Photo/Dmitri Lovetsky, Pool)

Russian President Vladimir Putin meets with representatives of international news agencies on the sidelines of the St. Petersburg International Economic Forum at the Constantine Palace in St. Petersburg, Russia, on Thursday, June 4, 2026. (AP Photo/Dmitri Lovetsky, Pool)

Russian President Vladimir Putin speaks to representatives of international news agencies on the sidelines of the St. Petersburg International Economic Forum at the Constantine Palace in St. Petersburg, Russia, on Thursday, June 4, 2026. (AP Photo/Dmitri Lovetsky, Pool)

People walk past a screen with an image of Russian President Vladimir Putin at an exhibition at the St. Petersburg International Economic Forum in St.Petersburg, Russia, on Thursday, June 4, 2026. (Anatoly Maltsev/Pool Photo via AP)

Russian President Vladimir Putin chairs a meeting on measures to support relatives of those killed and injured in the attack on a college in Starobilsk, of the Russia-controlled Luhansk region of Ukraine, at the Kremlin in Moscow, Monday, June 1, 2026. (Vyacheslav Prokofyev/Sputnik, Kremlin Pool Photo via AP)

A plumes of black smoke is seen over the port of St. Petersburg, Russia, Wednesday, June 3, 2026, after a Ukrainian drone attack. (AP Photo)

A plume of black smoke is seen over the port of St. Petersburg, Russia, Wednesday, June 3, 2026, after a Ukrainian drone attack. (AP Photo)