smog

A Chinese woman wearing mask walks in a shopping street during a hazy day in Beijing city, China, on Tuesday.  Beijing issued a red alert for smog, urging schools to close and residents to stay indoors for the second time in 10 days. Restrictions

Wu Hong/EPA

A Chinese woman wearing a mask walks in a shopping street during a hazy day in Beijing city, China, on Tuesday. Beijing issued a red alert for smog, urging schools to close and residents to stay indoors for the second time in 10 days

An elevation in the city of Sarajevo, Bosnia and Herzegovina, covered in a thick layer of fog, on Monday. Due to high levels of NO2 (nitrogen dioxide) in the air over the city and a certain meteorological condition, residents of Sarajevo were recommended to reduce their movement in the streets and to reduce car traffic

Fehim Demir/EPA

An elevation in the city of Sarajevo, Bosnia and Herzegovina, covered in a thick layer of fog, on Monday. Due to high levels of NO2 (nitrogen dioxide) in the air over the city and a certain meteorological condition, residents of Sarajevo were recommended to reduce their movement in the streets and to reduce car traffic

A woman wears a mask as she visits the Forbidden City during a sunny day in Beijing Friday, Dec. 18, 2015. Residents in the Chinese capital are preparing for its second smog red alert as a wave of smog is forecasted to settle over the city from Saturday to Tuesday.

Ng Han Guan/AP

A woman wears a mask as she visits the Forbidden City during a sunny day in Beijing Friday. Residents in the Chinese capital are preparing for its second smog red alert as a wave of smog is forecasted to settle over the city

Chinese Paramilitary guards stand on the stairs after Sheikh Mohammed bin Zayed al-Nahyan, Crown Prince of Abu Dhabi and UAE's deputy commander-in-chief of the armed forces leaves the Great Hall of the People in Beijing on December 14, 2015.

Fred Dufour/AFP

Chinese Paramilitary guards stand on the stairs after Sheikh Mohammed bin Zayed al-Nahyan, Crown Prince of Abu Dhabi and UAE’s deputy commander-in-chief of the armed forces leaves the Great Hall of the People in Beijing on Monday

A paramilitary policeman wearing a mask stands guard in front of the giant portrait of Chinese late chairman Mao Zedong, amid heavy smog after the city issued its first ever "red alert" for air pollution in Beijing, China, December 9, 2015. Picture taken December 9, 2015.

Reuters

A paramilitary policeman wearing a mask stands guard in front of the giant portrait of Chinese late chairman Mao Zedong, amid heavy smog after the city issued its first ever “red alert” for air pollution in Beijing, China

A woman wearing a protective mask against smog poses for photos at the Temple of Heaven Park in Beijing, China

Rolex de la Pena/EPA

A woman wearing a mask to protect against smog poses for photos at the Temple of Heaven Park in Beijing, China

Women wearing masks and other residents dance during their daily exercise amid the heavy smog in Beijing

Jason Lee/Reuters

Residents dance during their daily exercise amid the heavy smog in Beijing, China

A combo shows a morning commuter walking in front of the China Central Television (CCTV) building on a smoggy day and a sunny day

Damir Sagolj/Reuters

A combination photo shows a morning commuter walking in front of the China Central Television (CCTV) building on a smoggy day on December 1, 2015 (top), and on a sunny day on December 2, 2015 (bottom), after a fresh cold front cleared the smog that was blanketing Beijing, China.

Chinese man wears a protective face mask as he passes by the CCTV building on a day of heavy pollution on November 30, 2015 in Beijing, China. China's capital and many cities in the northern part of the country recorded the worst smog of the year with air quality devices in some areas unable to read such high levels of pollutants. Levels of PM 2.5, considered the most hazardous, crossed 600 units in Beijing, nearly 25 times the acceptable standard set by the World Health Organization. The governments of more than 190 countries are meeting in Paris this week to set targets on reducing carbon emissions in an attempt to forge a new global agreement on climate change.

Kevin Frayer/Getty Images

Chinese man wears a protective face mask as he passes by the CCTV building on a day of heavy pollution on Monday in Beijing, China. China’s capital and many cities in the northern part of the country recorded the worst smog of the year with air quality devices in some areas unable to read such high levels of pollutants

Motorists ride on a road as thick haze from forest fires shroud the city in Palangkaraya, Central Borneo, Indonesia, Tuesday, Oct. 27, 2015. The haze has blanketed parts of western Indonesia for about two months and affected neighboring countries like Singapore, Malaysia and Thailand

AP

Motorists ride on a road as thick haze from forest fires shroud the city in Palangkaraya, Central Borneo, Indonesia, Tuesday. The haze has blanketed parts of western Indonesia for about two months and affected neighboring countries like Singapore, Malaysia and Thailand

Lorries cross a bridge shrouded in haze in Klang, Malaysia

Olivia Harris/Reuters

Lorries cross a bridge shrouded in haze in Klang, Malaysia, on Wednesday. The thick so-called “haze,” caused by slash-and-burn clearances on the islands of Sumatra and Borneo, has pushed air quality to unhealthy levels in Malaysia and neighboring Singapore.

Spectators wearing masks watch men's singles match between David Goffin of Belgium and Andreas Seppi of Italy, on a polluted day at the China Open tennis tournament in Beijing...Spectators wearing masks watch men's singles match between David Goffin of Belgium and Andreas Seppi of Italy, on a polluted day at the China Open tennis tournament in Beijing, China, October 5, 2015.

Kim Kyung-Hoon/Reuters

Spectators wearing masks watch men’s singles match between David Goffin of Belgium and Andreas Seppi of Italy, on a polluted day at the China Open tennis tournament in Beijing, China on Monday

 BASE jumper leaps from the 300-metre high Kuala Lumpur Tower during the International Tower Jump in which more than 100 people take part, on a hazy day in Kuala Lumpur, Malaysia October 2, 2015. Slash-and-burn agriculture in neighbouring Indonesia has blanketed Malaysia and Singapore in a choking haze for weeks.

  © via Harris/Reuters

A BASE jumper leaps from the 300-metre high Kuala Lumpur Tower during the International Tower Jump in which more than 100 people take part, on a hazy day in Kuala Lumpur, Malaysia. Slash-and-burn agriculture in neighbouring Indonesia has blanketed Malaysia and Singapore in a choking haze for weeks. 

Students walk along a street as they are released from school to return home earlier due to the haze in Jambi, Indonesia's Jambi province, September 29, 2015 in this picture taken by Antara Foto. Indonesia has sent nearly 21,000 personnel to fight forest fires raging in its northern islands, the disaster management agency said on Tuesday, but smoke cloaks much of the region with pollution readings in the "very unhealthy" region in neighboring Singapore

Antara Foto/Wahdi Setiawan/Reuters

Students walk along a street as they are released from school to return home earlier due to the haze in Jambi, Indonesia’s Jambi province, Tuesday. Indonesia has sent nearly 21,000 personnel to fight forest fires raging in its northern islands

People do morning exercises on a polluted day in Jiaozuo, Henan province, March 16, 2015. China cannot relent on efforts to tackle pollution, though a rapid turnaround should not be expected, the environment minister told a news conference early this month during China's annual parliamentary meeting.

China Daily/Reuters

People perform morning exercises on a polluted day in Jiaozuo, Henan province, China on Monday.

An octopus-shaped kite flies over visitors on a smoggy day during a kite festival in Chongqing.

China Daily/Reuters

An octopus-shaped kite flies through the smog during a kite festival in Chongqing, southwest China

the Eiffel tower in central Paris through a haze of pollution.

Kenzo Tribouillard/AFP/Getty Images

Eiffel Tower in central Paris through a haze of pollution. More than 30 departments in France have been hit by maximum level pollution alerts since Thursday, prompting the ecology minister to say air quality was “an emergency and a priority for the government”.

Girls wearing masks on haze-covered Tiananmen Square in Beijing.  China's National Meteorological Centre issued a "yellow" smog alert for much of the country's north, the fifth consecutive day of heavy pollution which has slashed visibility and seen pollution reach hazardous levels.

AFP

China’s National Meteorological Centre issued a “yellow” smog alert for much of the country’s north, the fifth consecutive day of heavy pollution that has cut visibility and seen pollution reach hazardous levels, affecting areas such as Tiananmen Square (above) in Beijing.

Residents cover their face from dust as they ride their bicycles along a street on a hazy day in Zhengzhou, Henan province. Commentaries by two of China's most influential news outlets suggesting that an ongoing air pollution crisis was not without a silver lining drew a withering reaction on Tuesday from internet users and other media. The Global Times said smog could be useful in military situations, as it could hinder the use of guided missiles, while CCTV listed five "unforeseen rewards" for smog, including helping Chinese people's sense of humour.

Reuters

Cyclists cover their faces on a hazy day in Zhengzhou, Henan province, China. Two of the country’s most influential news outlets were criticised after trying to put a positive spin on China’s air pollution problem. The Global Times newspaper said smog could be useful in military situations, as it could hinder the use of guided missiles, while state broadcaster CCTV listed five “unforeseen rewards” of smog, including helping Chinese people’s sense of humour.

A traffic policeman signals to drivers during a smoggy day in Harbin, Heilongjiang province, October 21, 2013. The second day of heavy smog with a PM 2.5 index has forced the closure of schools and highways, exceeding 500 micrograms per cubic meter on Monday morning in downtown Harbin, according to Xinhua News Agency.

China Daily/Reuters

A traffic policeman signals to drivers during a smoggy day in Harbin, Heilongjiang Province. The second day of heavy smog forced the closure of schools and highways on Monday, according to Xinhua News Agency.