NASA uses satellites to monitor Earth's air pollution as "the world's largest single environmental health risk," according to a 2014 report from the World Health Organization. While ground-based monitoring stations collect data on air quality to assist local and state municipalities in identifying point sources of pollution, satellite measurements have proven essential for filling in missing data to provide consistent, near-real time, global maps of gaseous pollutant hot spots over cities, power plants, oil and gas fields - even shipping lanes - that would otherwise be invisible.
When Earth is viewed from space at night, brightest areas show the biggest cities and industrial areas. These areas correspond to increased air pollution.
Nitrogen Dioxide (NO2) is released into the air primarily by burning fossil fuels. It is unhealthy to breathe and reacts with other gases and sunlight to produce ground-level ozone, which is also unhealthy to breathe. NO2 imagery shows the greatest emissions around the world from:
Industry and vehicle exhaust over the United States, Europe, Asia, and an area in Southern Africa
Industry and fires over the Indian subcontinent
Slash-and-burn deforestation over Central and South America
Grassland fires and agricultural burning over sub-Saharan Africa and South America
Emissions controls have successfully decreased NO2 levels in some areas, such as the United States and western Europe since regulations began 30 years ago.
Places with growing populations and development, such as China and India, have air pollution that has dramatically increased over the past decade.
Natural sources of air pollution include volcanoes, sand storms, smoke from fires started by lightening.
There is also an introductory autorun ClimateBits video available that gives a quick overview of air quality designed to stand on its own or used within a docent show as an introduction. You can download it for SOS here