Killed more than 12,000 and hospitalized 150,000 Acidic fog formed from chemical reactions originating with the burning of coal and the release of sulfate particles

Donora, Pennsylvania air pollution event in 1948 https://www.smithsonianmag.com/history/a-darkness-in-donora-174128118/ Killed 20 people, sickened 7000, health effects persisted for decades. Emissions of hydrogen fluoride and sulfur dioxide from U.S. Steel's Donora Zinc Works and its American Steel & Wire plant were frequent occurrences in Donora, but they persisted for five days during this event, which lasted five days.

Using photometric reflectance data of >1,300 bird specimens drawn from natural history collections, we track relative ambient concentrations of atmospheric black carbon between 1880 and 2015 within the US Manufacturing Belt, a region historically reliant on coal and dense with industry. Our data show that black carbon levels within the region peaked during the first decade of the 20th century. Following this peak, black carbon levels were positively correlated with coal consumption through midcentury, after which they decoupled, with black carbon concentrations declining as consumption continued to rise. The precipitous drop in atmospheric black carbon at midcentury reflects policies promoting burning efficiency and fuel transitions rather than regulating emissions alone.

The US pioneered air quality control 1955 Air Pollution Control Act – provided federal funds to research the health effects of air pollution 1963 Clean Air Act – the first federal legislation regarding air pollution control 1970 Clean Air Act Authorized the establishment of National Ambient Air Quality Standards Address mobile and stationary sources Required states to implement plans to achieve standards Authorized requirements for control of motor vehicle emissions 1990 Amendments to the Clean Air Act of 1970 Authorized programs for Acid Deposition Control Established a program to phase out the use of chemicals that deplete the ozone layer. Clean Air Act of 1970 The enactment of the Clean Air Act of 1970 (1970 CAA) resulted in a major shift in the federal government's role in air pollution control. This legislation authorized the development of comprehensive federal and state regulations to limit emissions from both stationary (industrial) sources and mobile sources. Four major regulatory programs affecting stationary sources were initiated: the National Ambient Air Quality Standards (NAAQS, pronounced "knacks"), State Implementation Plans (SIPs), New Source Performance Standards (NSPS), and National Emission Standards for Hazardous Air Pollutants (NESHAPs). Furthermore, the enforcement authority was substantially expanded. The adoption of this very important legislation occurred at approximately the same time as the National Environmental Policy Act that established the U.S. Environmental Protection Agency (EPA). The EPA was created on December 2, 1970 in order to implement the various requirements included in these Acts.

2010 study

In one of the worst public health disasters in the world, Delhi, India, is suffering from a dire pediatric respiratory crisis. Nearly half of the city’s 4.4 million schoolchildren have irreversible lung damage from air pollution.

The city’s air is more than twice as polluted as Beijing’s, according to the World Health Organization. (India, in fact, has 13 of the world’s 25 most polluted cities, while Lanzhou is the only Chinese city among the worst 50; Beijing ranks 79th.) http://www.nytimes.com/2015/02/22/world/asia/polluted-air-cuts-years-off-lives-of-millions-in-india-study-finds.html?_r=0