Some of the worst air pollution since the great smog of 1952 will hit Britain in the next 24 hours – but how will it compare to other cities around the world?
The east of England and Midlands are the worst-affected areas but large swathes of England and Wales will see high levels of pollution on Thursday, the Department for Environment, Food and Rural Affairs (Defra) said.
The elevated pollution levels have been caused by a combination of light south-easterly winds, the continental air flow and dust which has blown up from the Sahara desert, a spokeswoman said.
On Wednesday north-west Norfolk should experience the highest level of air pollution. According to Defra’s pollution forecast, the people in the region can expect “very high” levels of pollution.
Other parts of East Anglia will experience “high” levels and parts of south-east England and the Humber region will experience “moderate” pollution.
But it could be worse, as Channel 4 News has found out.
Chinese Premier Li Keqiang “declared war” on pollution in a major policy address in March, but China has long struggled to strike a balance between protecting the environment and keeping up economic growth.
Rapid urbanisation brought dust from new housing and road building, while more traffic increased emissions. Slower wind speeds than usual in northern China were an additional contributing factor last year.
Beijing’s mayor promised in January to spend $2.4bn on improving air quality this year as part of an “all-out effort” to tackle pollution, though similar pledges in the past have brought little improvement.
Mexico City’s air pollution sent more than one million people to hospitals in 1999. Despite planting ten million trees and introducing alternative fuels for government vehicles, air pollution remains one of the most daunting environmental issues facing Mexico City.
More than three million vehicles on the road each day are mostly to blame, but so are industries and small factories, deforestation, and fires.
Ulaanbaatar in Mongolia is the coldest capital in the world. It has a population just over a twentieth of Beijing, yet according to the World Health Organization, it is considered the second most polluted city in the world – behind Ahvaz, Iran.
Its temperatures plunge when winter sets in and people begin to seek heat by firing up old, coal-powered stoves. Millions of stoves ignited around the same time produce a smog so thick, it hangs like a yellow cloud you can see from any hilltop.
Pollution is believed to be responsible for one in ten deaths and a 45 per cent rise in the number of patients with respiratory illnesses between 2004 and 2008.
Ahvaz in south Iran is one of the world’s most polluted cities, according to a recent air quality survey by the World Health Organization. The city, with a population of about 1.2m people, had the highest count of small airborne particles out of 1,100 urban areas around the world.
The hub of Iran’s oil production, Ahwaz is marked by thick orange smog that often saturates the city. Iranian officials blame its high levels of air pollution on the presence of US forces during the Iran-Iraq war, but other researchers point to the city’s heavy oil, metal and petrochemical industries.
Santiago in Chile deals with substantial amounts of smog each year. This blanket of pollution is caused by a plant powering one of the largest copper mines in the world.
Atmospheric and geographic conditions worsen the problem. With Santiago nearly surrounded by mountains, covered by a layer of warm air, and with little rain or wind, smog gets trapped. The result is a brown cloud of pollution permanently hanging over the city.
In Delhi, India the pollution, created by vehicles and industrial plants, is particularly severe in winter, when low temperatures keep emissions close to the ground.
Thick blankets of smog covered the capital through most of March, leading to bleak days, hundreds of cancelled flights and a cacophony of coughs on the city’s streets.
The previous Delhi government had put together a plan to tackle air pollution, involving better monitoring mechanisms, cutting the number of vehicles on the roads, and stricter parking policies. But the plan remains unimplemented.
A dense fog covered London between the 5 and 8 December 1952. Trying to keep warm, Londoners piled extra coal into their fireplaces, sending plumes of black, sooty smoke into the air that mixed with clouds of exhaust from factories and coal-burning power plants.
Over the next five days a thick haze hovered over the streets, penetrating homes and offices. The great smog led to several changes in practices and regulations, including the Clean Air Act 1956. London Plane Trees were also introduced to help clean the air after the great smog.
The 1948 Donora smog in Pennsylvania, US, killed 20 people and sickened 7,000 people – half the town’s population.
The smog was caused by a decrease in temperature combined with hydrogen fluoride and sulphur dioxide emissions from steel plants. The Town of Donora’s business district is today empty, and full of crumbling and decayed buildings.