Many of us would like to think that air pollution is a problem that can simply dissipate after a few days. But the health effects from it linger, and what we can’t see can kill us. Earth scientists studying air pollution have just released a map that shows air pollution deaths over time on a global scale.

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The stark map shown above was created at NASA Earth Observatory by data visualizer and designer Robert Simmon. This atmospheric computer model shows the average number of deaths per 386 square miles per year due to air pollution between 1850 and 2000. It’s based on data from Jason West, an assistant professor of environmental sciences and engineering at University of North Carolina. He and his colleagues published their findings earlier this year in  Environmental Research Letters. (Hat tip to Gawker.)

“Dark brown areas have more premature deaths than light brown areas,” the NASA map explanation reads. The map shows that air pollution has been particularly deadly in eastern China, northern India and Europe — all areas where urbanization has added lots of fine particulate matter to the atmosphere since the Industrial Revolution began.

Blue areas on the map are locations where the scientists found a decline in premature deaths relative to 1850. They attribute those numbers to improvements in air quality. In the southeastern United States, the scientists think the change could have been caused by a decline in biomass burning in the past 160 years.

Seeing some blue areas made me think that the outlook isn’t entirely bleak for humanity. New York officials recently reported that the city is experiencing the best air quality in 50 years. They credit an effort to get buildings to convert to cleaner fuels for heating. With less pollution causing cardiovascular and lung problems, the city estimates that 800 lives have been saved and 2,000 hospital visits prevented each year, Kate Taylor reported in the New York Times.

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But just how bad is air pollution in general? West and his team found that toxic outdoor pollution known as fine particulate matter directly causes 2.1 million deaths worldwide every year. That makes this is one deadly problem that won’t just blow over.

Image: A model estimate of the average number of deaths per 386 square miles due to air pollution between 1850 and 2000. Credit: Robert Simmon, NASA Earth Observatory.