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Rising carbon dioxide levels in the atmosphere do a lot of damage—heat waves, droughts, wildfires, superstorms. Now it appears there’s another knock-on effect that had never before been measured. According to a new study in the journal Air Quality, Atmosphere and Health, the changing chemistry of the atmosphere could be leading to changing chemistry in our blood—with potentially dangerous effects.

If CO2 is indeed messing with our blood, it’s no wonder. During the early rise of Homo sapiens, carbon dioxide levels in the atmosphere measured a consistent 280 parts per million (ppm). Those conditions prevailed until roughly the middle of the 18th century when the Industrial Revolution began pouring greenhouse gasses into the air from factory smokestacks.  By 1900, CO2 levels had risen to nearly 300 ppm; by 1980, that figure had jumped to nearly 330 ppm. Since then the numbers have exploded, standing at 425 ppm today.

That’s very bad news for the health of the planet—and equally bad for the health of our bodies. Every breath we take—indoors or out—draws in more carbon dioxide than our bodies were originally adapted to cope with. To determine just what the impact of this is, environmental geoscientist Phil Bierwirth, of Australian National University in Canberra, and environmental health scientist Alexander Larcombe, of Curtin University, took advantage of a 21-year survey—from 1999 to 2020—conducted by the U.S. National Health and Nutrition Examination Survey (NHANES), during which government investigators sampled the blood of 7,000 subjects every other year to see how the body responded to all manner of environmental pollutants. 

The period the NHANES researchers surveyed was a particularly bad one for the planet when it comes to carbon dioxide emissions, since in just those 21 years, U.S. CO2 levels rose from 369 ppm to 420 ppm. In their work, Bierwirth and Larcombe were looking for rising levels of serum bicarbonate, a chemical marker associated with rising levels of CO2—and they found just that, with a 7% jump in bicarbonate over the 21 years.

Much in the way oceans can become more acidic as they absorb more carbon dioxide, the same can be said for blood. “Bicarbonate,” said Larcombe in an email to TIME, “is the body's main chemical ‘shock absorber’ for keeping blood from becoming too acidic, and a rising level is an indicator of the body compensating for more CO2.”

But bicarbonate can do only so much, and even over relatively small stretches, higher levels of CO2 in the blood can take a toll. “From short-term studies at moderately elevated CO2 (the sort of levels common in poorly ventilated rooms),” wrote Larcombe, “that means headache, tiredness, and declines in concentration and decision-making. Over longer periods, animal studies raise the possibility of oxidative stress, inflammation, tissue calcification in the kidneys and arteries, and effects on bone.”

At the same time bicarbonate levels have been rising in the blood, calcium and phosphorus levels have been falling, the study found. In addition to producing higher levels of bicarbonate, the body responds to rising carbon dioxide by drawing CO2 molecules out of the blood and storing them in bones in the form of carbonate—an ion composed of one carbon atom and three oxygen atoms. Phosphorus and calcium, which assist in this process, are drawn from blood into bone as well.

“Falling calcium and phosphorus in blood is what you'd broadly expect if that [CO2] storage process were being asked to do more work,” says Larcombe. Here too, bodily functions may suffer. “Low calcium (hypocalcaemia) produces muscle cramps, lethargy, numbness and tingling in the fingers, and disturbances of heart rhythm. Low phosphorus (hypophosphataemia) can lead to weakness, fatigue and impaired oxygen delivery.” The good news is, we’re not there yet, with Larcombe stressing that such symptoms would occur only at “much higher CO2 concentrations than today’s atmosphere.”

What’s more, at the moment, our bodies are doing a good job of adjusting to the level of CO2 that does exist in the atmosphere—even if just barely—since most people are not experiencing the warning symptoms Larcombe describes. But the famed CO2 hockey stick—the y-axis graph that shows greenhouse gasses and global temperatures steadily rising—is pushing us ever further into the danger zone. 

As with so much concerning the environment, it will be young people who will pay the highest price for the mess preceding generations have made. Not only are growing bodies more susceptible to environmental toxins, but babies born into the current world will be alive for more of the latter decades in which atmospheric CO2 will be at its highest—assuming more stringent curbs on greenhouse emissions are not put in place now. Most projections call for atmospheric CO2 concentrations to reach 500-plus PPM by mid-century, a level that will exceed tolerable carbon dioxide levels in the blood, Larcombe says. 

The answer—again and always—is to undertake the hard work of curbing greenhouse gas output before anything like those astronomical levels of CO2 are reached. That’s not a job many decision makers in high-polluting countries have shown any consistent willingness to take on—the result being that the world has now briefly breached well-intentioned stop signs like the Intergovernmental Panel on Climate Change’s proposal to limit global temperatures to no more than 2°C above those of pre-industrial levels. The problem is emissions and temperature limits are not the only ones in play here; so too are biological ones.

“I think that what we are seeing is because our bodies are not adapting,” said Bierwirth in a statement that accompanied the release of the study. “Maybe we can never adapt.”

Correction, Aug. 20

The original version of this story misspelled a scientist's surname, and misstated his university affiliation. It is Alexander Larcombe not Lacrombe. He works at Curtin University, not the University of Western Australia.

Ukrainian President Volodymyr Zelenskyy is facing a major internal political challenge after a recently dismissed defense minister called for a wartime presidential election. But holding an election during an ongoing war would pose enormous legal and logistical challenges—and it may not be possible at all.

Ex-Defense Minister Mykhailo Fedorov's challenge comes amid an ongoing war with Russia. While Zelenskyy’s five-year term was scheduled to end in May 2024, elections have been suspended under martial law since Russia’s full-scale invasion of Ukraine in February 2022.

Fedorov posted a nine-minute video online Tuesday, demanding that Ukraine “restore a full democratic process even amid a prolonged war.”

Read More: Chalk One Up for Ukraine

“Democracy cannot be held hostage by Russia. We are fighting precisely because we want to remain a free European state,” Fedorov said. “We must find a legal, safe, and ‌realistic mechanism which will allow Ukraine to renew its full democratic process even in the conditions of ​a long war.”

Fedorov, 35, was a longtime ally of Zelenskyy before he was abruptly fired in July amid mounting friction with military leadership, and his departure sparked days of protests. On Wednesday, Yevhenii Khmara was confirmed as the new defense minister.

Although Fedorov did not mention Zelenskyy in the video, he issued a blistering critique of Ukrainian leadership, saying that the country is in a “systemic crisis of governance” and alluding to corruption. The accusation comes just after Zelenskyy fired deputy chief of staff Iryna Mudra on Wednesday amid a money-laundering investigation. 

This is not the first time that Zelenskyy has come under fire for the suspended elections. Last year, President Donald Trump attacked him as a “dictator without elections.” However, the Ukrainian President has steadfastly denied that he is using the war to cling to power and said he would be open to an election if it could be safely and securely held.

“I am now asking—and I am stating this openly—for the United States, possibly together with our European colleagues, to help me ensure security for holding elections,” he told reporters on WhatsApp at the end of 2025. He said there would need to be “guarantees” from the United States and Russia to ensure safe voting practices.

Zelenskyy had yet to respond to the comments from Fedorov as of Wednesday afternoon, but experts say it is unlikely that an election can take place in Ukraine.

What stands in the way of holding elections in Ukraine?

Historically, very few countries have held elections in wartime, Konstantin Sonin, a professor at the University of Chicago Harris School of Public Policy, tells TIME, adding that it's very unlikely for an election to happen in Ukraine.

A ceasefire would first be needed—but Sonin says it’s unlikely that Ukraine would trust any assurances from Russia.

“I cannot imagine that Ukraine would rely on any kind of guarantees from Russia to have elections,” Sonin tells TIME. “[Concerns about] Russian election interference are half of the problem.”

Sonin says that there are also many “practical limitations” to putting the necessary technology and infrastructure in place for a secure vote.

“The main limitation is that it's difficult to count votes from the occupied territories,” he says. 

Russia occupies roughly 19% of Ukraine. According to Ukrainian figures from January of that year, there could be as many as 4.5 million adults living in those occupied territories. Millions more Ukrainians have been internally displaced.

Who could challenge Zelenskyy?

It’s unlikely that any challenger would successfully unseat the Ukrainian President amid the ongoing war, Sonin says.

“Zelenskyy won elections in 2019, defeating the incumbent, and since then navigated an extremely complex terrain of Ukrainian politics,” he says. “He would defeat any other candidate.”

Sonin says in years past there were potential presidential alternatives—including General Valerii Zaluzhnyi—who might have been perceived as someone who could “prosecute the war better.”

Zaluzhnyi long held that he had no political ambitions; however, in July, Ukrainska Pravda reported that Zaluzhnyi told Zelenskyy he would run if elections were held in the fall, citing sources close to both men. Sources told the outlet that Zaluzhnyi had changed his mind because he didn’t want to disregard the trust that people had placed in him.

“Ukraine is not losing, and there is so much hope,” Sonin says. “I do not see how Zelenskyy would not win these elections.”

Recent polling, however, complicates Sonin’s assessment. SOCIS, a polling firm, found that Zelenskyy would finish first in the first round in an election against Fedorov, Zaluzhnyi, and Kyrylo Budanov—the current chief of staff for the President, who has not publicly expressed any intention to run. Zelenskyy would capture 22% of the vote as compared with Zaluzhnyi’s 21% and Fedorov’s 13%. 

Because none of the candidates would command the majority, which is required in Ukraine, the top two contenders would move on to a runoff election. And if the vote did reach a second round, the poll projected a loss for Zelenskyy. He ranked behind Fedorov, Zaluzhnyi, and Budanov in the prospective runoff modeled by SOCIS.

Recent developments in the war could also shift those political dynamics. In the past few weeks, Ukraine has expanded its aerial war against Russia. It started ramping up production of long-range missiles that can travel up to 1,500 miles (2,400 km) from the border and has already targeted several key retail and energy hubs in and around Moscow.

According to Ukrainian media, Zelenskyy’s approval rating has dipped since the war started, but still remains close to 60%.

South Korean Foreign Minister Cho Hyun said Wednesday that Seoul was given no notice before President Donald Trump announced that he would be scaling back joint military operations between the two countries.

“Neither our government nor U.S. officials knew what President Trump wrote on his Truth Social," Cho told the National Assembly Committee on Foreign Affairs and Unification. "We were not notified in advance.” 

Cho added, however, that Defense Minister Ahn Gyu-back was in “close consultation” with his U.S. counterparts regarding the reductions to South Korea-U.S. military exercises. 

Read More: Trump’s South Korea Shift Tests a Key U.S. Alliance

Trump on Sunday announced in a Truth Social post that he had instructed Defense Secretary Pete Hegseth to “substantially reduce” joint military exercises with South Korea, citing the country’s refusal to participate in the U.S.-Israel war against Iran and his “very good relationship” with North Korean leader Kim Jong Un. 

Trump called the joint exercises “costly” and “totally inappropriate and hostile” to North Korea, which he said has been “unthreatening and respectful” throughout his presidency. 

Both the Pentagon and South Korea have confirmed that joint operations have been reduced following Trump’s announcement.

A Defense Department official tells TIME that the U.S. has “substantially reduced” Exercise Ulchi Freedom Shield—an annual, large-scale training dating back roughly 50 years that combines multiple sectors of the military designed to prepare a U.S.-Korean joint response to international threats. The Ulchi exercise began on Monday and was supposed to last for 11 days, but will now end on Aug. 21, one week earlier than originally scheduled, the official says. 

“Associated live-training events have been reduced, with certain events canceled or converted to simulations,” the official adds, noting that “training that enhances tactical capability” will continue. “These adjustments preserve essential readiness and training objectives. There will be no degradation to U.S. training objectives.”

South Korea's Joint Chiefs of Staff also confirmed that it had agreed to the reductions at the request of the U.S.

North Korea has largely shrugged off the reductions, saying that they don’t change the geopolitical posture of either the U.S. or South Korea towards itself. 

"We are paying greater attention to the reality that joint military exercises between the U.S. and South Korea have continued and are still ongoing, and this is an unmistakable expression of hostility toward North Korea," Kim Yo Jong, the sister of the country’s leader, said on Wednesday, according to the state-run Korean Central News Agency. She added that Pyongyang had “no interest whatsoever" in Trump’s announcement and that “reducing the scale or duration of the drills does not change the provocative and aggressive nature of the military exercises.”

Trump said in the Oval Office on Monday, following his order to the Pentagon, that he had spoken with Kim Jong Un about a scheduled conversation. Kim Yo Jong said on Wednesday, however, that she was "unaware" and knew “absolutely nothing” about recent communication between Trump and Kim Jong Un. 

On Wednesday, Trump said that he would meet with Kim Jong Un this year, but did not elaborate further. 

“He has 57 very powerful nuclear weapons,” Trump said to reporters on the White House grounds, referring to North Korea’s arsenal. “Should have never allowed it to happen, they should never have allowed it. If I were president, I never would have allowed it.”

Trump, who met Kim Jong Un face-to-face three times during his first term, has maintained a friendly relationship with the North Korean leader throughout his presidencies. "I have a great relationship with Kim Jong Un,” Trump said in August of last year. “I hope it stays that way, I think it will. I have a very good relationship. I understand him.” 

Amid his cordial relations with Kim Jong Un, Trump has repeatedly demanded that North Korea suspend its nuclear arms program, a request Pyongyang has said is off the table. Trump seems determined to negotiate towards that goal with the North Korean leader. 

The President’s recent move to halt joint exercises resembles one he made in his first term.  Following a summit in Singapore in 2018 during which Trump met with Kim Jong Un, making him the first sitting president to hold a summit with a North Korean leader, Trump suspended the Ulchi exercise with South Korea in the name of diplomacy with North Korea.