A person crosses Westminster Bridge during foggy weather in London, Britain, February 7, 2023. REUTERS/Toby Melville TPX IMAGES OF THE DAY 

A bus is driven across Westminster Bridge past the Houses of Parliament during foggy weather in London, Britain, February 7, 2023. REUTERS/Toby Melville TPX IMAGES OF THE DAY 

People cross Westminster Bridge as fog shrouds the Houses of Parliament in London, Britain, February 7, 2023. REUTERS/Toby Melville 

Birds fly along the River Thames during foggy weather in London, Britain, February 7, 2023. REUTERS/Toby Melville 

A couple embraces on Westminster Bridge as fog shrouds the Houses of Parliament in London, Britain, February 7, 2023. REUTERS/Toby Melville 

Fog shrouds the Houses of Parliament in London, Britain, February 7, 2023. REUTERS/Toby Melville 

A person records images on Westminster Bridge as fog shrouds the Houses of Parliament in London, Britain, February 7, 2023. REUTERS/Toby Melville 

An aerial view of residential buildings shrouded in smog in New Delhi, India, November 7, 2022. REUTERS/Altaf Hussain 

Residential buildings under construction are seen shrouded in heavy smog in Noida, on the outskirts of New Delhi, India, November 6, 2022. On November 6 at 10:00 IST, Sector 116 in Noida, , the closest monitoring station, registered a PM 2.5 reading of 398. REUTERS/Adnan Abidi SEARCH "ABIDI POLLUTION INDIA" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. 

Traffic moves along a highway shrouded in heavy smog in New Delhi, India, November 3, 2022. REUTERS/Adnan Abidi 

Traffic moves along a highway shrouded in heavy smog in New Delhi, India, November 3, 2022. REUTERS/Adnan Abidi 

Trees are seen shrouded in heavy smog on the banks of river Yamuna in New Delhi, India November 3, 2022. REUTERS/Adnan Abidi 

Smoke shrouds the view of the Interstate 90 bridge in Seattle, Washington, U.S., October 20, 2022. REUTERS/Matt Mills McKnight 

Fog shrouds the city during early morning hours in Nur-Sultan, Kazakhstan September 14, 2022. REUTERS/Pavel Mikheyev
 

Fog shrouds the city during early morning hours in Nur-Sultan, Kazakhstan September 14, 2022. REUTERS/Pavel Mikheyev
 

Fog shrouds the city during early morning hours in Nur-Sultan, Kazakhstan September 14, 2022. REUTERS/Pavel Mikheyev 

Smoke shrouds the skyline as wildfires contribute to poor air quality in Vancouver, British Columbia, Canada, September 12, 2022. REUTERS/Jennifer Gauthier 

A person on a paddle board uses a paddle as smoke shrouds the skyline as wildfires contribute to poor air quality in Vancouver, British Columbia, Canada, September 12, 2022. REUTERS/Jennifer Gauthier 

People fly a kite at the beach as smoke shrouds the skyline as wildfires contribute to poor air quality in Vancouver, British Columbia, Canada, September 12, 2022. REUTERS/Jennifer Gauthier 

Kayakers row as smoke shrouds the skyline as wildfires contribute to poor air quality in Vancouver, British Columbia, Canada, September 12, 2022. REUTERS/Jennifer Gauthier 

Heavy smoke shrouds the skyline as wildfires contribute to poor air quality in Vancouver, British Columbia, Canada, September 12, 2022. REUTERS/Jennifer Gauthier 

A float plane is seen as smoke shrouds the skyline as wildfires contribute to poor air quality in Vancouver, British Columbia, Canada, September 12, 2022. REUTERS/Jennifer Gauthier 

A cyclist bikes along the seawall as smoke shrouds the skyline as wildfires contribute to poor air quality in Vancouver, British Columbia, Canada, September 12, 2022. REUTERS/Jennifer Gauthier 

A pedestrian walks along the seawall as smoke shrouds the skyline as wildfires contribute to poor air quality in Vancouver, British Columbia, Canada, September 12, 2022. REUTERS/Jennifer Gauthier 

Cyclists bike along the seawall as smoke shrouds the skyline as wildfires contribute to poor air quality in Vancouver, British Columbia, Canada, September 12, 2022. REUTERS/Jennifer Gauthier 

A float plane is seen as smoke shrouds the skyline as wildfires contribute to poor air quality in Vancouver, British Columbia, Canada, September 12, 2022. REUTERS/Jennifer Gauthier 

Heavy smoke shrouds the view of B.C. Place Stadium as wildfires contribute to poor air quality in Vancouver, British Columbia, Canada, September 12, 2022. REUTERS/Jennifer Gauthier 

Smoke shrouds a multi-storey apartment block near the burning shopping mall Galaktika following recent shelling in the course of Ukraine-Russia conflict in Donetsk, Ukraine, August 24, 2022. REUTERS/Alexander Ermochenko 

Buildings and houses stand shrouded in smog as authorities ordered traffic restrictions due to air pollution in Mexico City, Mexico, on May 3, 2022. REUTERS/Edgard Garrido 

Azteca stadium is pictured shrouded in smog as authorities ordered traffic restrictions due to air pollution in Mexico City, Mexico, on May 3, 2022. REUTERS/Edgard Garrido 

Buildings stand shrouded in smog as authorities ordered traffic restrictions due to air pollution in Mexico City, Mexico, on May 3, 2022. REUTERS/Edgard Garrido 

Buildings stand shrouded in smog while an aircraft flies over them as authorities ordered traffic restrictions due to air pollution in Mexico City, Mexico, on May 3, 2022. REUTERS/Edgard Garrido 

Buildings stand shrouded in smog as authorities ordered traffic restrictions due to air pollution in Mexico City, Mexico, on May 3, 2022. REUTERS/Edgard Garrido 

Buildings and houses stand shrouded in smog as authorities ordered traffic restrictions due to air pollution in Mexico City, Mexico, on May 3, 2022. REUTERS/Edgard Garrido 

Buildings stand shrouded in smog as authorities ordered traffic restrictions due to air pollution in Mexico City, Mexico, on May 3, 2022. REUTERS/Edgard Garrido 

A Cal Fire water dropping helicopter draws water from the Pacific Ocean, seen through the smoke shrouding the coastline as the Colorado Fire burns near Big Sur, California, U.S. January 22, 2022. REUTERS/Peter DaSilva 

A Cal Fire water dropping helicopter flies through smoke-shrouded skies as the Colorado Fire burns near Big Sur, California, U.S. January 22, 2022. REUTERS/Peter DaSilva 

A general view shows the fog-shrouded city of Almaty, Kazakhstan January 12, 2022. REUTERS/Pavel Mikheyev 

Cable cars are seen against the backdrop of the fog-shrouded city of Almaty, Kazakhstan January 12, 2022. REUTERS/Pavel Mikheyev 

Fog shrouds streets and buildings in the city of Omsk, Russia December 18, 2021. Picture taken December 18, 2021. REUTERS/Alexey Malgavko 

A man drives a car along a street shrouded in fog in the city of Omsk, Russia December 18, 2021. Picture taken December 18, 2021. REUTERS/Alexey Malgavko 

Fog shrouds streets and buildings in the city of Omsk, Russia December 18, 2021. Picture taken December 18, 2021. REUTERS/Alexey Malgavko 

A pedestrian walks under an illuminated signboard in a street shrouded in fog in the city of Omsk, Russia December 18, 2021. Picture taken December 18, 2021. REUTERS/Alexey Malgavko 

A view shows a block of flats shrouded in fog in the city of Omsk, Russia December 18, 2021. Picture taken December 18, 2021. REUTERS/Alexey Malgavko TPX IMAGES OF THE DAY 

Fog shrouds streets and buildings in the city of Omsk, Russia December 18, 2021. Picture taken December 18, 2021. REUTERS/Alexey Malgavko 

An aerial view shows the Bolshoy Obukhovsky Bridge shrouded in fog in Saint Petersburg, Russia December 18, 2021. Picture taken December 18, 2021 with a drone. REUTERS/Anton Vaganov 

Vehicles are seen shrouded in smog on a highway in New Delhi, India, November 18, 2021. REUTERS/Anushree Fadnavis 

Vehicles are seen shrouded in smog in New Delhi, India, November 17, 2021. REUTERS/Anushree Fadnavis 

Humayun's Tomb is seen shrouded in smog in New Delhi, India, November 16, 2021. REUTERS/Anushree Fadnavis 

Buildings are seen shrouded in smog in New Delhi, India, November 16, 2021. REUTERS/Anushree Fadnavis 

Boys fly a kite as residential houses are seen shrouded in smog in New Delhi, India, November 15, 2021. REUTERS/Adnan Abidi REFILE-QUALITY REPEAT 

An office complex building is seen shrouded in smog in Noida on the outskirts of New Delhi, India, November 15, 2021. REUTERS/Adnan Abidi REFILE-QUALITY REPEAT TPX IMAGES OF THE DAY 

A man rows a boat as buildings shrouded in smog are seen in the background on the outskirts of Delhi, India, November 15, 2021. REUTERS/Adnan Abidi 

A couple poses during a pre-wedding photo shoot near India's Presidential Palace which is shrouded in smog, in New Delhi, India, November 5, 2021. REUTERS/Anushree Fadnavis TPX IMAGES OF THE DAY 

A man rides a motorbike along a road shrouded in smog in Noida, India, November 5, 2021. REUTERS/Anushree Fadnavis 

Residential buildings are seen shrouded in smog in Noida, India, November 5, 2021. REUTERS/Anushree Fadnavis