Air pollution kills millions of people around the world. In the western United States, the air is getting worse.
The World Health Organization has released stringent new standards for air pollution levels, and data suggests that the air in many parts of the United States contains levels of hazardous materials much higher than those recommended by people. standards.
The WHO says air pollutants are responsible for more than 4 million premature deaths a year worldwide, calling it “one of the greatest environmental health risks”.
But an NBC News analysis of air pollution levels shows that air quality across the country on average is already below WHO guidelines, updated in September for the first time in over 15 years.
While nationwide air quality is already worse than the new threshold, it is particularly bad in California, Oregon, Nevada, Idaho and Washington, where particle levels are more than double the level. the recommended limit. The new directive lowers the threshold for particles in the air, among several other pollutants, halving the maximum recommended amounts.
This form of particulate matter is a mixture of microscopic solids and liquid droplets known as PM2.5, named after its size of 2.5 microns in diameter, or about one-thirtieth the width of a human hair. Commonly found in smoke from forest fires and vehicle exhaust fumes, the pollutant has been linked to hospital admissions linked to respiratory illnesses and increased mortality.
PM2.5 levels vary by region in the United States, but the national average in 2020 was around 8 micrograms per cubic meter, up from 13 in 2000, according to the Environmental Protection Agency. The new WHO guidelines set the recommended level at 5.
In the EPA’s western region, California and Nevada averaged 11.7 micrograms last year. The agency’s region of Washington, Oregon and Idaho averaged 11.9 micrograms.
“When you inhale these particles, they are able to penetrate deeper into your respiratory system than larger particles,” said Michael Kleeman, professor of civil and environmental engineering at the University of California at Davis. “Once there, the tiny particles trigger a cascade of biochemical processes that cause inflammation. “
He said high levels of PM2.5 in smoke are linked to adverse health effects, and once the particles enter the lungs, they can also pass into the bloodstream and even organs.
The U.S. standards, last updated in 2012, are slightly less stringent than current – and old – WHO guidelines, but the EPA said comparing the two standards was not that straightforward.
“Direct comparisons of [EPA] standards with WHO guidelines are difficult and often impractical, ”EPA deputy press secretary Tim Carroll wrote in an emailed statement to NBC News, adding that there were differences in the pollutants measured and how the data was averaged.
According to him, this distinguishes the EPA from the WHO guidelines, which, as the global body notes, are not “legally binding standards” but a tool for member states.
Kleeman said the US standards are based on studies that compare populations of areas with different levels of pollution and look at the likelihood of dying sooner. He said the WHO is building on new types of studies that use satellite data to estimate the exposure to pollutants of millions and millions of people.
“What they are finding is that there are still health effects below the current US standard,” he said.
According to an analysis of EPA data, average pollutant levels in the United States have continued to decline since at least 2000.
That number changes when looking at regional data, which shows the western United States with levels just below the EPA standard, while the rest of the country is in a safer range.
And while wildfires have turned the skies orange in California, that smoke can spread to parts of the East Coast, affecting air quality for nearly 3,000 miles.
Despite this, Kleeman said the air quality in the United States is much better than it was decades ago.
“Comparing Los Angeles in the 1970s to today is much better. It’s the result of things like catalytic converters, improved vehicle technology and factory controls, ”he said.
Kleeman said PM2.5 levels in the 1970s could reach 50 micrograms per cubic meter in California. According to the EPA, these levels haven’t gotten much higher than 20 micrograms in the past 20 years.
This decline was largely attributed to the Clean Air Act of 1970, a series of laws that paved the way for air quality standards in the United States.
“The United States does not adjust our standards to WHO guidelines. The Clean Air Act requires the EPA to periodically review the science on which the U.S. standards are based and the standards themselves.
EPA administrator Michael Regan said last summer the agency was reviewing a Trump administration decision to maintain existing air quality standards, but the review process is expected to last until spring 2023.
Kleeman said the important and obvious sources of air quality have already been addressed and low-level improvements present challenges.
“It is difficult to achieve small, continuous improvement in air quality without truly revolutionizing the energy system.