Worldwide, rising levels of air pollution increase the chances that people will die early, a sweeping new study finds. In Australia, which has historically low levels of air pollution, an increase in sooty air led to a sharp rise in the rate of earlier deaths.

More air pollution means more deaths, even at low levels of air pollution and short exposures to it, according to the study, which measured particulate matter and daily death rates in 652 cities in 24 countries over the course of 30 years. It is the largest international study on the short-term impacts of air pollution on death conducted to date, and was published in The New England Journal of Medicine.

A lot of research already exists on how this kind of pollution makes people sick. Breathing in particulate matter from dust, ash, and the burning of fossil fuels and can damage the heart and lungs. It’s been linked to chronic lung and heart problems, as well as early death. Today’s study highlights that even low levels of particulate matter can be dangerous.

The results are particularly resonant now, as the Amazon rainforest burns at some of the fastest rates ever recorded in the country

Today’s study found that death rates rose sharply as air pollution did — a scary finding, especially in Brazil, which ranked second only to Australia in increased mortality rates. In Brazil, the Amazon rainforest is currently burning at some of the fastest rates ever recorded in the country. And those forest fires generate particulate matter. Smoke from the fires was so heavy that it darkened the skies in the city of São Paulo. Brazilian president Jair Bolsonaro has pledged to open up the Amazon to agribusiness and mining interests, making it vulnerable to people slashing and burning to clear land.

To determine the deaths were actually early, researchers compared daily mortality rates over the study period. Compared to the daily death rates at the start, there was a rise in deaths on days when air pollution increased.

If you look at the percentages, the increases seem small. When it comes to all causes of death, mortality rates across the board rose .44 percent when the amount of coarse particulate matter increased slightly. For fine particulate matter, which is smaller and can enter into the deep lungs when inhaled, mortality rates rose .68 percent when concentrations increased. But less than 1 percent of the global population is still millions of people.

“If we’re looking at a population of one million people in a city, well 1 percent is significant and it can affect a lot of people,” Eric Lavigne, a co-author of the study, tells The Verge. Lavigne is a professor at the University of Ottawa and a senior epidemiologist for Canada’s Public Health Agency.

there’s still plenty of room for improvement

Some countries in the analysis, like the US, already have measures in place to keep air pollution in check; despite that, they saw higher increases in death rates as pollution went up. That means there’s still plenty of room for improvement. “We can still have public health impact by getting cleaner than we already are,” says John Balmes, a spokesperson for the American Lung Association who teaches at the University of California in San Francisco and Berkeley.

Balmes adds, “a relatively small risk that affects the entire population can be just as important in terms of public health as a stronger risk factor that not everybody experiences [like smoking].”

Excluding studies like this “would set a dangerous precedent for environmental policy”

The US Environmental Protection Agency is currently reassessing its national air quality standards. While studies like this one suggest public health is a good reason to limit air pollution, it’s not clear this paper (and others like it) will be considered by the US in that analysis. The Trump administration has pushed to limit the types of evidence it considers into those that fall into a particular scientific approach — and this one doesn’t fall into that framework. But excluding studies like this one “would set a dangerous precedent for environmental policy,” Balmes writes in his editorial.

The Environmental Protection Agency did not respond to an email from The Verge requesting comment.