Human inputs of air pollutants have increased at an unprecedented rate in the last century. The following two images represent two different ways that human activity has contributed to outdoor air pollution.
Burning large amounts of coal in power plants contributes to photochemical smog, which consists of an unhealthy mixture of sulfur dioxide, sulfuric acid, and VOCs This type of air pollution is a major contributor to the gigantic South Asian brown cloud and, according to the World Bank, has contributed to more than 250,000 annual deaths in China alone.