The emergence of great factories and consumption of immense quantities of coal gave rise to unprecedented air pollution, and the large volume of industrial chemical discharges added to the growing load of untreated human waste. Chicago and Cincinnati were the first two American cities to enact laws ensuring cleaner air in 1881. Pollution became a significant issue in the United States in the early twentieth century, as progressive reformers took issue with air pollution caused by coal burning, water pollution caused by bad sanitation, and street pollution caused by the three million horses who worked in American cities in 1900, generating large quantities of urine and manure. As historian Martin Melosi notes, the generation that first saw automobiles replacing horses saw cars as "miracles of cleanliness".Patrick Allitt, A Climate of Crisis: America in the Age of Environmentalism (2014) p 206 By the 1940s, automobile-caused smog was a significant issue in Los Angeles.
The emergence of great factories and consumption of immense quantities of coal gave rise to unprecedented air pollution, and the large volume of industrial chemical discharges added to the growing load of untreated human waste. Chicago and Cincinnati were the first two American cities to enact laws ensuring cleaner air in 1881. Pollution became a signific:ant issue in the United States in the early twentieth century, as pro.gressive reformers took issue with air pollution caused by coal burning, water pollution caused by bad sanitation, and street pollution caused by the three million horses who worked in American cities in 1900, generating large quantities of urine and manure. As historian Martin Melosi notes, the generation that first saw automobiles replacing horses saw cars as "miracles of cleanliness".Patrick Allitt, A Climate of Crisis: America in the Age of Environmentalism (2014) p 206 By the 1940s, automobile-caused smog was a significant issue in Los Angeles.