Factory smokestacks release billows of smoke into an autumn landscape of clear skies and bare trees.

US Steel’s coke manufacturing facility in Clairton, Pennsylvania. Photo: Joseph A

London to Pittsburgh: The Politics and Beauty of Polluted Skies

By the early 20th century, when Claude Monet was painting London’s bridges and buildings, its fogs had been sickening and periodically killing its citizens for centuries. The rapid increase in coal consumption in London after 1600 created a city so polluted that it made its own weather patterns: scientists think that the city’s increased incidence of fog and thunderstorms throughout the 19th century was attributable at least in part to pollution.1  The smoke blocked out the sun so much that scientists think it contributed to the spread of the “English disease,” rickets, an illness caused by vitamin D deficiency.2  Low visibility caused coaches, carts, and trains to crash into one another. People fell into canals and rivers and sometimes drowned, while others were sent into choking spasms that lasted weeks at a time.

Yet London’s fog, as dangerous and unhealthy as it was, was a kind of bucket list item for the Gilded Age adventure tourist. It was tolerated, even celebrated, as an unsavory but inevitable consequence of London’s place as a center of industry and the heart of a global empire. London’s fog is the backdrop of Sherlock Holmes mysteries and the stories of Charles Dickens. Some newcomers actually liked the fog: an American visitor said it gave everything a “golden halo” and made him feel as if he were looking at “the figures of fading frescoes.”3  It is this uniquely modern visual landscape that brought Claude Monet to London, where the “black, brown, yellow, green, purple fogs” that he found enthralled him. “My practiced eye has found that objects change in appearance in a London fog more and quicker than in any other atmosphere, and the difficulty is to get every change down on canvas,” he later told one art dealer.4 

Painting of a bridge seen through smoke and fog.
Claude Monet, Waterloo Bridge, London, 1903

Monet might have found a similar atmosphere in Pittsburgh at the time. It was the smokiest city in the Western Hemisphere by 1850. When the air pollution was bad, street lights would need to be turned on during the day. The soot was so heavy it would turn men’s white collared shirts gray by midday. The city’s rapid development in the late 19th century was tied to its proximity to easy-to-reach coal reserves and to the rivers connecting it with the expanding Western frontier. Immigrant laborers from southern and eastern Europe and the American South were also indispensable to the growth of the city. But the city’s industries needed one other resource to flourish: the virtually unlimited ability to pollute the skies and the lungs of those workers and their families. Pollution was a fact of life, and then as now, it was interpreted as a sign of economic vitality.

But what to do about it? The region’s entire political economy was based on extracting, exploiting, and burning as much mineral wealth as possible. In some ways, it worked spectacularly well. Pittsburgh’s population grew from 80,000 in 1860 to 500,000 just 50 years later. Pittsburgh steel was used to build the Brooklyn Bridge and the locks of the Panama Canal and to arm the US military during World War II. But the cost of cleaning and lighting a sky that rained down layers of soot was obvious, and calls to clean up the air persisted.

Overhead view of an intersection with the light from neon signs, street lights, and car headlights visible against the darkened atmosphere.
Corner of Liberty and Fifth Avenues, 12:20 p.m., ca. 1940. Photo: Smoke Control Lantern Slides, University of Pittsburgh Library Systems

Environmental protection policies began to take hold during the 20th century. After World War II, Pittsburgh enacted its first smoke abatement policies.5  These succeeded in encouraging businesses and homeowners to use cleaner technology and to replace coal with cleaner fuels like natural gas. Still, large mills continued to pollute the air.

The 1948 Donora “Death Fog,” which killed 20 people and sickened thousands more when an air temperature inversion trapped toxic industrial smoke in the town’s valleys for four days, spurred the creation of the first national clean air laws and helped lead to the creation of the Environmental Protection Agency.6  But it wasn’t until the collapse of the steel industry during the 1970s and 1980s that bigger improvements in air quality came to the city. Air quality in Pittsburgh has improved greatly since that time. Airborne particulate matter measurements are close to half what they were then. Much of this has to do with federal clean air regulations and the closing of coal-fired power plants upwind of the city.

Still, Pittsburgh has some of the worst air in the United States. Its topography and meteorology can hold air pollution in place as they did during the steel era, amplifying its impact on peoples’ health. The city’s remaining heavy industry is responsible for a large portion of this pollution. Coal-fired power plants, chemical plants, and steel mills all contribute to the problem.

River scene with barges in the foreground and factory smokestacks as a backdrop.
Joseph Pennell, Pittsburgh No. 3, 1909

One of the biggest contributors is U.S. Steel’s Clairton coke works, the largest coke plant in the United States. It was built in 1901 and churns out 4.3 million tons of coke, a key ingredient in steelmaking, each year.7  To make coke, steel companies bake coal to break down impurities. What is left is almost pure carbon. Baking coal also creates a sulfurous, potent vapor called coke oven gas, which is classified as a “known human carcinogen” by the EPA.8  Allegheny County has the highest levels of coke oven gas anywhere in the United States. U.S. Steel “cleans” its coke oven gas at the Clairton plant. But this process can break down, as it did in late 2018, when a fire ripped through a control room at the plant. The company refused to idle the plant during repairs, arguing that it would have been dangerous and could have ruined hundreds of millions of dollars’ worth of equipment.

For more than three months, U.S. Steel continued to produce coke oven gas without cleaning it. It burned the gas in flares at several nearby plants along the Monongahela River. The result was several months of at times unhealthy air for the more than 100,000 people who live within five miles of the flares. One of the main culprits was sulfur dioxide, which is created when coke oven gas is burned. When sulfur dioxide mixes with water, as in Pittsburgh’s dewy air or inside of human lungs, it becomes sulfuric acid, which can irritate the lung passages. Thousands of people complained that it was hard for them to breathe. Some people wouldn’t even take their animals outside, and children with no previous respiratory problems developed asthma. The Wall Street Journal said that the event had taken Pittsburgh back to the “bad old days” of the decades before modern air regulations.9 

Barges, smokestacks, storage towers, and other factory structures seen from across a river.
U.S. Steel’s Clairton coke works. Photo: Roy Luck

Although U.S. Steel eventually repaired its pollution controls, the event revived an old, uncomfortable question: how badly does Pittsburgh want clean air? The city has embraced the knowledge economy. Uber and Google are here. Carnegie Mellon is a nexus for engineering. The city has come to be regarded as a destination for dining and cultural activities. Yet U.S. Steel still employs 3,000 people at its Mon Valley Works, which include Clairton, offering some of the last well-paying, unionized jobs left in the local economy. After a June mishap at the Clairton coke works shut down pollution controls for one day, official and public responses showed how weary many in the region are of putting up with bad air. Allegheny County Chief Executive Rich Fitzgerald said that he was “disappointed” by the plant’s record of violations and outages. The county health department immediately issued an emergency order to U.S. Steel: clean up or close down. The plant got its pollution controls back online within a day, but the message was clear: people are watching now in ways that they might not have been before.

The fracking industry will soon add a new source of air pollution to the region: petrochemicals. Shell is building an enormous chemical plant in Beaver County called an ethane cracker, which will turn natural gas into tiny plastic pellets. It will also be a major producer of volatile chemicals that are released into the air. Other plants are expected to follow it. This plastic will soon join steel, coal, and natural gas as one of Pittsburgh’s industrial products. The question remains: how much pollution will the Pittsburgh region accept from these industries?

London, like Pittsburgh, is much cleaner than it was during Claude Monet’s lifetime. But the city of eight million people still struggles with air pollution levels that regularly fail the European Union’s public health standards. In response, the city is encouraging drivers in the city’s center to switch to electric cars. There, as here, the fight for clean air continues.

Additional Information

Monet and the Modern City is on view at Carnegie Museum of Art until September 2, 2019.


  1. Peter Brimblecombe, The Big Smoke: A History of Air Pollution in London Since Medieval Times (New York: Methuen, 1987), 110–11.
  2. Minyong Zhang et al., “‘English Disease’: Historical Notes on Rickets, the Bone–Lung Link and Child Neglect Issues,” Nutrients 8 no.11 (November 2016): 722, https://doi.org/10.3390/nu8110722.
  3. Brimblecombe, The Big Smoke, 116–17.
  4. Quoted in Grace Seiberling, Monet in London (Seattle: University of Washington Press, 1988), 62.
  5. Cliff I. Davidson, “Air Pollution in Pittsburgh: A Historical Perspective,” Journal of the Air Pollution Control Association 29 no.10: 1035–1041, https://doi.org/10.1080/00022470.1979.10470892.
  6. Elizabeth Guenther, “Donora Death Fog: The Crisis that Led to Modern Air Pollution Laws,” ChEnected, American Institute of Chemical Engineers, last modified October 27, 2011, https://www.aiche.org/chenected/2011/10/donora-death-fog-crisis-led-modern-air-pollution-laws.
  7. “Mon Valley Works Clairton Plant,” Locations, United States Steel Corporation, accessed August 8, 2019, https://www.ussteel.com/locations/mon-valley-works-clairton-plant.
  8. “Coke Oven Emissions,” United States Environmental Protection Agency, last updated January 2000, https://www.epa.gov/sites/production/files/2016-09/documents/coke-oven-emissions.pdf.
  9. Kris Maher, “Pittsburgh Air-Quality Problem Recalls the Bad Old Days,” The Wall Street Journal, updated March 12, 2019, https://www.wsj.com/articles/pittsburgh-air-quality-problem-recalls-the-bad-old-days-11552388400.