Trump’s tweet boasting the country's air quality came shortly after federal scientists released an extensive report indicating that the U.S. limit for PM2.5 might need to be lowered from the 2012 level set under the Obama administration. | Carolyn Kaster/AP Photo Trump touts U.S. air quality — under Obama

President Donald Trump on Monday tweeted that the U.S. has the best air quality in the world “BY FAR!” — but the map he shared on Twitter showed the air quality from 2016, the final year of Barack Obama's presidency.

And while the U.S. has lower levels of the single pollutant depicted on the map than most other parts of the world, the underlying United Nations data show the U.S. actually isn't in the top five nations with the cleanest air.


The cleanest would be Finland, which boasted in July that its measurement of the pollutant called fine particular matter was the lowest on the planet at 6 micrograms per cubic meter of air, putting it slightly ahead of Estonia, Sweden, Canada, Norway and Iceland.

The pollutant, also called “PM2.5,” consists of various particles smaller than 2.5 micrometers, significantly tinier than the width of a human hair. It's emitted by cars, power plants, construction sites and other industrial activities, as well as barbecues, tobacco smoking and some natural sources like volcanoes and forest fires. PM pollution has been linked to increases in premature death, heart attacks, aggravated asthma and other respiratory illnesses. It also causes haze, contributes to acid rain and destroys nutrients in soil.

Morning Energy newsletter The source for energy and environment news — weekday mornings, in your inbox. Email Sign Up By signing up you agree to receive email newsletters or alerts from POLITICO. You can unsubscribe at any time. This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

And it's also only one of many types of pollution that have worried experts in recent decades. The U.S. has made strides in combating PM2.5, but remains the No. 2 emitter in the world behind China of carbon dioxide, one of the main greenhouse gases driving climate change.

The map included in Trump's tweet — which was retweeted by acting EPA Administrator Andrew Wheeler — appears to have come from an April report from the World Health Organization that modeled concentration of that PM2.5. The White House did not return requests for comment on the president’s tweet.

Trump’s tweet also came shortly after his own federal scientists released an extensive report indicating that the U.S. limit for PM2.5 might need to be lowered from the 2012 level set under the Obama administration. Most areas of the U.S. meet that latest annually averaged standard for PM2.5 of 12 micorgrams per cubic meter, according to EPA, although car-heavy Los Angeles and a few industrial regions in other states are still lagging.

The EPA last week released a 1,900-page report that indicated scientific evidence of health effects from PM2.5 at concentrations as low as 5 micrograms per cubic meter. The report itself doesn’t call for a lower pollution standard, but it will provide more evidence for public health advocates who have called for stronger regulations.

Former Administrator Scott Pruitt in May directed EPA to finish a new review of the PM standards by December 2020. Last week’s fall update to the federal regulatory agenda indicated EPA will not propose whether to tighten that standard until at least late 2019, if not later.

Studies show that certain events can trigger local spikes in PM2.5 pollution — such as a 2015 study by the National Oceanic and Atmospheric Administration that found July 4 fireworks send air pollution skyrocketing across the nation. Another study in 2014 measured brief but massive increases in PM2.5 levels for spectators of a building demolition in Frankfurt, Germany.

Zack Colman contributed to this report