Parts of Asia are chocking under a thick layer of smog, leading at least one country to experiment in extreme forms of weather modification in an attempt to clear the toxic brown skies.
Thailand, South Korea, China, India and Hong Kong are all facing unhealthy and even hazardous levels of pollution as weather patterns, coal heating and emissions contribute to the annual crisis.
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According to the World Health Organization (WHO), nine out of every 10 people on the planet breathe air containing a high level of pollutants, with the worst affected regions being Africa and Asia.
Authorities in the Thai capital Bangkok are expected to deploy planes with special rainmaking capabilities -- a technique known as cloud seeding -- on Tuesday, with the aim of easing pollution in some parts of the city, according to the Bangkok Post.
The concept involves injecting clouds with small amounts of inert chemicals, such as silver iodide, in order to increase rainfall. In recent years, it has been used by nations that suffer from severe seasonal pollution levels, including China.
Several areas of Bangkok, a sprawling and heavily congested city of 8 million, are seeing high levels of PM2.5 pollution particles -- microscopic particles smaller than 2.5 micrometers in diameter which are considered particularly harmful because they are small enough to lodge deep into the lungs and pass into other organs.
In recent days, the levels have been hovering around 150-200 microgrammes per cubic meter, which is considered unhealthy on the Air Quality Index (AQI), according to CNN meteorologists. The World Health Organization considers AQI levels under 25 to be acceptable for humans to breathe regularly.
Firefighters Monday blasted water from high-pressure cannons around Bangkok's City Hall and other areas, as part of short term efforts to ease the hazardous smog, the Post reported. There is debate as to whether water is effective in washing away the finer and more dangerous PM2.5 particles.
For five consecutive days, high levels of fine dust have blanketed parts of South Korea, according to local media. Over the past 48 hours, the cloud of fine dust has reached very unhealthy levels of between AQI 150-225, CNN meteorologists said.
Local governments in ten cities have enacted emergency measures, such as limited vehicles on the road and reducing emissions output at factories, while people in Seoul covered their faces with masks and avoided going outside unless necessary.
"The air is so murky and my throat hurts that I even feel depressed," one South Korean citizen told the Yonhap News agency.
Experts have pointed to the usual suspects causing what has become an annual crisis, including factories, car exhausts, coal heating and a stagnant air mass. Pollution from factories and emissions being blown across the Yellow Sea in China have also exacerbated the problem.
Cities across industrial areas in northeast China were put on "orange alert" over the weekend for heavy smog by the country's central meteorological administration, the South China Morning Post reports.
Visibility was reportedly down to 200 meters in some areas and even down to 50 meters in the worst affected regions. The smog is affecting Tianjin (about 80 miles from Beijing) and cities across Hebei, Shandong, Henan, Anhui, Jiangsu and Hubei provinces.
Shanghai posted an unhealthy AQI reading of 183 on Tuesday. Hong Kong also saw unhealthy levels of pollution over the weekend.
In recent years, China has pushed efforts to curb its annual smog, which affects large swathes of the country during winter. In late 2017, China announced a major curtailing of small-scale coal burning -- one of the biggest sources of pollution in winter -- by shifting around 3 million households in northern China to natural gas.
Coal is by far the main source of heating in the country, providing 83% of heat in 2016 according to Greenpeace, so by cutting this off, many households were without alternative sources of fuel.
Yet the need to cut indoor coal emissions is extremely important, with the World Health Organization estimating that millions of premature deaths each year are caused by indoor air pollution created by the burning of solid fuels such as coal.
It's not just coal that could be causing the problem, however. A joint study by US and Chinese scientists found that formaldehyde -- which comes from gas stove and kerosene heater emissions, and cigarette smoke, among other sources -- could be playing an outsized role in contributing to China's pollution problem.
On Tuesday, parts of the city reached hazardous levels exceeding AQI 300. It's a problem that has plagued the Indian capital for years.
Following the Diwali Hindu festival of lights in November, the US Embassy in Delhi reported pollution levels of 999 -- or beyond the index reading of a standard AQI chart, which tops out at a "hazardous" level of 500.
The pollution particularly affects those who work outside. "I have trouble breathing. By the time I return home, I have chest pain, I'm coughing," Rana, who has been an auto rickshaw driver for 24 years, told CNN in November of his experience driving during the winter smog.
Last week, the Indian government launched a five-year plan called the National Clean Air Program, which aims to reduce levels of air pollution by 30% from 2017 levels by 2024.
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