Air Pollution's Discovery: A Historical Perspective

Air pollution has been recognised as a threat to human health since the time of Hippocrates, around 400 BC. The discovery and understanding of air pollution, however, evolved over the centuries, with the industrial revolution accelerating the magnitude of emissions and the geographical spread of pollutants. The 1952 Great Smog of London, caused by coal combustion, resulted in thousands of premature deaths and illnesses, bringing the issue to the forefront and leading to the first Clean Air Act in 1956. Ancient civilisations like the Romans contributed to air pollution through metallic pollutants, and medieval air quality was impacted by smelting. The 19th century saw the emergence of smog in cities, causing deaths and continuing into the 20th century with notable incidents like the 1948 Donora smog episode and the 1969 Cuyahoga River fire, which galvanised environmental activism and legislation. Today, Asia, particularly China, faces significant air pollution challenges, and the COVID-19 pandemic provided a brief respite from industrial and transport emissions.

Air pollution's ancient history

Air pollution has been a concern since ancient times, with the earliest recorded instances dating back to the time of Hippocrates, around 400 BC. Written accounts from this period and the following two millennia attest to the recognition of air pollution as a threat to human health. Ancient civilizations, including the Romans, were not exempt from the detrimental effects of air pollution, as evidenced by the discovery of blackened lungs in mummified tissues from Egypt, Peru, and Great Britain, likely caused by wood fires in ancient homes.

The Romans, in fact, have been credited with being among the first to introduce metallic pollutants into the atmosphere, a problem that would persist and intensify in the centuries to come. By the 1600s, smoke from burning coal was already damaging buildings in London and other major cities. This issue was further exacerbated by the invention and widespread adoption of the steam engine, which marked a significant shift in pollution levels.

As cities became increasingly populated during the 19th century, industrialised urban centres in Europe and the United States faced a new challenge: waste from industries and factories. Rivers like the Tawe in Wales were grossly contaminated by a range of pollutants, including "alkali works, copper works, sulfuric acid liquid, [and] sulfate of iron." This period also witnessed the emergence of "smog"—a combination of smoke and fog—which led to numerous deaths in cities such as New York and London.

The turn of the 20th century brought with it a wave of federal legislation aimed at tackling air pollution. The Air Pollution Control Act of 1955 was the first federal attempt in the United States to address this issue, spurred by incidents like the 1948 Donora smog episode that caused 20 deaths and affected the health of over 7,000 people. The Clean Air Act of 1963 in the US and the UK's Clean Air Act of 1956 were further efforts to combat the growing problem of air pollution, with the latter specifically targeting pollution and smog from coal burning.

The Industrial Revolution's impact

The Industrial Revolution, which began in the late 18th century, brought about significant advancements and progress in society. This period marked a shift towards a manufacturing-based economy, leading to increased production, improved transportation systems, and enhanced living and working conditions. However, the Industrial Revolution also had a profound impact on the environment, particularly in terms of air pollution.

During the Industrial Revolution, there was a rise in the use of mechanized factory systems, chemical manufacturing, iron production, and steam and water power. This transition to new manufacturing processes led to an increased need for natural resources such as coal and iron. The burning of coal and other fossil fuels in factories, homes, and power plants became a major source of air pollution. As industrialization progressed, urbanization intensified, and cities became heavily industrialized and increasingly polluted.

The Second Industrial Revolution, from the late 19th to early 20th centuries, introduced electricity, steel production, and the internal combustion engine. This phase further drove mass production and the growth of heavy industries, particularly in Europe and North America. Countries like the UK, Germany, and France rapidly industrialized, resulting in exponential increases in energy consumption and resource extraction. The cumulative environmental strain of each phase of industrialization caused significant increases in air pollution, with highly polluted cities becoming a defining issue.

The Industrial Revolution marked the start of our intensive use of fossil fuels, which has been the driving force behind climate change. The consequences of this environmental impact are still felt today, with large-scale carbon emissions continuing to drive global warming. Europe and North America, as the first regions to experience rapid industrial growth, were the most impacted by emissions during the second half of the 20th century. They dominated global emissions until controls on sulfur and nitrogen oxide emissions began to take effect, and environmental awareness increased.

While the Industrial Revolution brought about many advancements, it also had a significant impact on air pollution. The increased use of fossil fuels, industrialization, and urbanization led to higher emissions and polluted cities. Today, the focus has shifted towards controlling and reducing emissions to mitigate the adverse effects of air pollution on human health and the environment.

20th-century air quality issues

Air pollution has been a recognized threat to human health since as early as 400 BC. However, the Industrial Revolution accelerated the magnitude of emissions of primary pollutants, and the problem of air pollution became more severe in the 19th century. The widespread use of coal as a source of energy, the increasing use of steam engines, factories, and railroads all contributed to worsening air quality. Industrialized cities across Europe and the United States experienced a new kind of pollution due to waste from industries and factories.

In the 20th century, air pollution continued to be a significant problem. In 1948, twenty people were asphyxiated and over 7,000 became seriously ill due to severe air pollution in Donora, Pennsylvania. This incident, along with the 1969 Cuyahoga River fire, led to the creation of the Air Pollution Control Act of 1955, the first federal attempt to control air pollution. The Clean Air Act of 1990 further addressed the issue by setting limits on the discharge of air pollutants from industrial facilities and motor vehicles and addressing acid rain and ozone depletion.

The Federal Water Pollution Control Act, commonly called the Clean Water Act, was also enacted in 1972 to provide funding for improving sewage treatment plants and set limits on the discharge of pollutants into the water. The Oil Pollution Act of 1990 prohibited the discharge of oil into navigable rivers. These laws have significantly reduced pollution levels and improved air quality since the 1980s. However, in the early 21st century, as controls on emissions of sulfur and nitrogen oxides in Europe and North America began to take effect, emissions in East and South Asia grew, dominating global emissions.

Despite this progress, approximately 140 million people in the United States lived in counties with pollution levels above the primary NAAQS in 2023. Continuous low-level exposure to pollutants remains a concern for experts, and global emissions of ammonia continue to grow due to a lack of abatement actions. Nevertheless, the EPA has developed national programs that will achieve significant reductions in air emissions and improve health, longevity, and quality of life for Americans when fully implemented.

Legislation and activism

Air pollution has been a recognized issue since the time of Hippocrates, around 400 BC. However, it was during the Industrial Revolution that the magnitude of emissions and the geographical spread of contributing countries accelerated, with highly polluted cities becoming a defining issue.

The Clean Air Act of 1963 in the US encouraged scientific research and expanded the federal government's role in air pollution control. President Johnson remarked that the legislation would help "halt the trend toward greater contamination of our atmosphere." This was followed by other air pollution laws in the 1960s, including the Motor Vehicle Air Pollution Control Act of 1965 and the Air Quality Act of 1967, which addressed regional air pollution. The Clean Air Act of 1970 was a significant milestone, resulting from over two decades of citizen activism. Citizens played a crucial role in achieving this legislation by writing letters, raising public awareness, and expressing their concerns to senators and industry officials.

In the UK, the Clean Air Act of 1956 was enacted following the Great Smog of 1952 in London, which is associated with 12,000 deaths. The UK government also produced films and other messages to inform the public about pollution's dangers.

The 1969 Cuyahoga River fire in the US further spurred grassroots activism, resulting in a wave of federal legislation dedicated to tackling air and water pollution. This activism led to the creation of the Federal Water Pollution Control Act (commonly called the Clean Water Act) in 1972, which provided funding to improve sewage treatment plants and set limits on industrial discharges into the water.

The anti-pollution movement in the US gained momentum in the 1970s, with a shift towards apocalyptic critiques of consumerism and waste. Films like the Emmy-winning "Countdown to Collision" (1972) reflected this discourse. Environmental organizations like Environmental Action were also influential, drafting an 18-point "Plan for Clean Air" with the support of grassroots organizations and public figures.

Today, air pollution remains a serious threat to world health, and experts continue to address the challenges posed by continuous low-level exposure to pollutants.

Global air pollution today

Air pollution has been a recognized threat to human health since as early as 400 BC, when it was discussed by Hippocrates. However, the issue of air pollution became more prominent during the Industrial Revolution, which saw a significant increase in emissions of primary pollutants. This period witnessed the rise of highly polluted cities, with London experiencing a major smog event in 1952.

Today, air pollution remains a critical global challenge, with 99% of the world's population breathing unhealthy air. The 2024 World Air Quality Report revealed that 91% of 138 countries and regions exceeded the WHO's annual PM2.5 guideline value, with Central and South Asia among the most polluted regions. The primary sources of air pollution vary depending on the city and local regulations, but industrial activities, agricultural practices, and transportation contribute significantly to the problem.

Industrial facilities, such as manufacturing factories, mines, oil refineries, and power plants, release nitrogen oxides (NOx), hydrogen sulfide, volatile organic compounds (VOCs), and particulate matter, leading to increased ozone and smog levels. The agricultural sector, driven by the increasing demand for animal products and per capita food, also contributes to fine-particulate air pollution, particularly through the heavy use of fertilizers.

Transportation emissions, primarily from fuel combustion in motor vehicles, aircraft, and ships, significantly impact air quality. The rise in economic activity and standards of living has led to a corresponding increase in transportation demand, contributing to elevated levels of fine particulate matter (PM2.5), ozone, and nitrogen dioxide (NO2). Natural sources of air pollution, such as volcanic activity, wildfires, and dust or sandstorms, also play a role, with their impact varying depending on the local environment.

While legislation like the Clean Air Act in the United States has helped reduce pollution, continuous low-level exposure to pollutants remains a concern for experts. Addressing air pollution requires a combination of regulatory measures, technological advancements, and a shift towards more sustainable practices in various sectors, including industry, agriculture, and transportation.

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