The unprecedented masses of smoke created by wildfires in Australia returned to their homeland after crossing the Pacific Ocean and going around the world, NASA said.
The agency's Google Earth images show the trail of brown smoke as it made its way around the world. According to NASA, the smoke had traveled half the Earth and South America on January 8.
Fire-induced thunderstorms provided a path for smoke to enter the stratosphere, traveling thousands of miles from Australia and affecting global atmospheric conditions.
Wood smoke contains some of the same toxic chemicals as urban air pollution, along with small particles of steam and soot 30 times thinner than human hair.
The fires have claimed at least 28 lives since September, destroyed more than 2,600 houses and burned more than 25.5 million acres of land, mainly in the state of New South Wales.
Hospital admissions increased in cities affected by smoke, as some patients suffered asthma for the first time in their lives. The government distributed 3.5 million free masks that exclude particles.
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Despite regularly broadcasting public health warnings, several tennis players in the qualifying tournament for the Australian Open in Melbourne have been affected by smoke. A player fell to his knees in a coughing attack and had to withdraw from his match.
In the United States, about 20,000 people die prematurely every year due to chronic smoke exposure from forest fires. It is likely to double by the end of the century, according to NASA-funded scientists.
Research suggests that children, the elderly and people with health problems are at greater risk.
Contributing: The Associated Press
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