NASA has released a visual image of how particles emitted by natural events such as forest fires and erupting volcanoes affect the Earth's atmosphere.
The American space agency has used satellite imagery and ground sensors to stake out the movement of "millions of unseen particles that float through the air", reports the Daily Mail.
These particles, called NASA aerosols, are in the form of both liquid and solid emissions that "hang in the atmosphere," the paper says.
According to Engadget, the aerosol Earth map [pictured top] marks black carbon emissions in red. These particles can be emitted by forest fires, which is perhaps the reason why there is a high concentration of them in California after this year's forest fires.
Meanwhile, corrosive sea salt particles "raised by storms" appear in blue and dust is highlighted in purple, says the technical site.
Aerosols marked in the image fly "high above our heads" and are often invisible, says the tech news site BGR.
It is unlikely that people under the aerosol clouds will breathe something harmful, but according to the website, the potentially dangerous materials "have to come down somewhere". Weather patterns often push aerosols closer to the ground, affecting air quality. This can cause breathing problems in some people.
Most particles seem to have been released by natural events beyond our control, but Nasa says that some of the carbon black emissions are caused by human activity.
For example, the clouds of carbon over Africa are mostly caused by farmers who light numerous small fires to keep their crops going, according to the space agency.
Carbon aerosols are also a common by-product of vehicle emissions and the manufacturing industry.