Smog

Residents are being urged to take extra precautions as smog worsens during triple-digit temperatures.

The National Weather Service has issued an alert over poor air quality in four cities in the Golden State.

Ozone pollution is expected to reach a concerning level on Friday.

Poor air quality was expected throughout the day on Thursday.

Canada is already facing a record year for wildfires, with areas of the northeastern U.S. choking on the smoke. But what is causing such prolonged blazes?

The Environmental Protection Agency's proposal aims to reduce nitrogen oxide emissions from trucks.

The move is usually reserved for severe human rights violations.

New Delhi has the worst air quality in the world.

Reports of a cloud of darkness blocking out the Sun at noon above northern Siberia have raised questions.

2,000 people have been told to evacuate and more could follow if authorities fear escape routes are under threat.

The eruption could also bring acid rain.

Air in China on Wednesday was nearly too dangerous to breath.

Between 25 and 41 percent of nitrogen oxide is emanating from agricultural lands in California.

The number of days when smog posed a high health risk have doubled in the last year.

Killer smog in China has paralyzed some of its top cities in the past—so much so that its defense now includes the world's biggest air purifier.

Air pollution may be a major contributor to declining kidney health, and even lead to kidney failure.

Temperatures in the Golden State could reach as high as 122 degrees.

Experts couldn't measure just how bad the air pollution was because the sandstorm caused traditional measuring instruments to break.

Over 126 million Americans—about 40 percent—live in areas that fail to meet environmental standards.

The report also suggests building huge ventilation tunnels to create wind which will lift the smog from the city

As many as 24 cities are on red alert, while 21 are on orange alert.

Poor air quality has plagued the country's north, triggering a red alert in Beijing.

Another tightening of EPA standards this year could trip up automakers.

The 'pigeon air patrol' record the nitrogen dioxide levels produced by London traffic.

The warning comes just a week after the city's first ever red alert.

A cold front swept away smog that had been lingering for days before it arrived.

The announcement marks the first red alert in the city's history.

China says it will clean up its act, but when it's good and ready.

There are just a few minutes on the clock, says Ed Begley Jr., but the game is definitely not over

The agency's scientists warned against setting the limit at this level.