Air Pollution's Historical Rise: A Global Concern

Outdoor air pollution has been a significant problem since the time of Hippocrates, around 400 BC. However, it became a more pressing issue during the Industrial Revolution, when industrialized cities across Europe and the United States experienced a new kind of pollution from industrial waste and factories. This trend continued into the 20th century, with episodes of smog (a combination of smoke and fog) causing many deaths in cities like New York and London. Today, outdoor air pollution is the world's fourth-largest risk factor for early death, causing 4.2 million premature deaths annually. The problem is particularly acute in low- and middle-income countries, which bear 89% of the premature death burden.

Air pollution recognised as a threat to human health since 400 BC

Air pollution has been a significant problem for centuries, with recognition of its threat to human health dating back to ancient times. As early as 400 BC, during the time of Hippocrates, the detrimental effects of air pollution on human health were acknowledged. This awareness persisted through the centuries, with successive written accounts of air pollution emerging from different countries over the following two millennia.

While the understanding of air pollution's impact has evolved, the issue itself is not new. Early humans, even before the time of Hippocrates, would have experienced discomfort from smoke and combustion gases from open fires, particularly in enclosed spaces. The development of chimneys in the 12th century marked a significant milestone in improving indoor air quality, as dwellings transitioned from open fires.

However, the Industrial Revolution brought about a new wave of air pollution, as industrial growth and the widespread use of fossil fuels led to a significant increase in pollutants released into the atmosphere. This trend was particularly evident in cities, where industrial activities were concentrated. The consequences of this pollution were stark, with incidents like the lethal haze in Donora, Pennsylvania, in 1948, causing severe respiratory and cardiovascular issues for thousands of residents and resulting in nearly 40 deaths.

The situation in Donora reflected a broader pattern of air pollution resulting from industrial development. It sparked widespread concern, prompting scientists to investigate the link between air pollution and health more closely. This led to the passing of legislation aimed at reducing air pollution, including the Clean Air Act Amendments in 1970, which established national air quality standards in the United States.

Today, air pollution remains a critical global issue, with outdoor air pollution being the fourth-largest risk factor for early death worldwide. It continues to wreak havoc on human health and the planet, with fine particles released from burning fossil fuels harming respiratory and cardiovascular systems and contributing to climate change. While advancements in technology and scientific understanding have led to improvements in air quality in some regions, the ongoing climate crisis threatens to exacerbate air pollution problems, particularly in highly populated countries like China and India.

Industrial Revolution: cities experienced a new kind of pollution

Air pollution has been a concern since ancient times, with early humans likely aware of the dangers of smoke and combustion gases from fires in enclosed spaces. The ancient Greek physician Hippocrates, around 400 BC, recognised air pollution as a threat to human health. However, it was during the Industrial Revolution that cities experienced a new kind of pollution, with industrial waste and factory emissions becoming a significant problem.

As cities became more populated towards the end of the 19th century, industrialised cities across Europe and the United States were faced with a unique challenge. The air pollution in these cities was no longer just from fires and smoke but also from waste generated by industries and factories. This marked a turning point in the history of air pollution, with the outdoor air quality deteriorating rapidly.

The Industrial Revolution, which began in the late 18th century, brought about large-scale mechanisation and the use of new industrial processes. While this revolution led to significant economic growth and technological advancements, it also had detrimental effects on the environment. The burning of fossil fuels, such as coal, and the release of industrial chemicals contributed to the worsening air quality in urban areas.

Cities like London and New York experienced episodes of "smog" in the 19th century, a combination of smoke and fog that led to numerous deaths. This issue persisted well into the 20th century, with major incidents of air pollution occurring in Donora, Pennsylvania in 1948, and the Cuyahoga River fire in 1969. These events served as catalysts for the implementation of air pollution control measures, such as the Air Pollution Control Act of 1955 and the Clean Air Act of 1990.

Today, air pollution remains a critical issue, with outdoor air pollution contributing to millions of premature deaths globally each year. While there have been improvements in reducing global average mortality rates from air pollution, the climate crisis threatens to exacerbate the problem. Addressing air pollution is crucial for protecting public health and mitigating its impact on the environment.

19th-century smog episodes in cities caused many deaths

Air pollution has been a recognized threat to human health since the time of Hippocrates, around 400 BC. However, the issue of outdoor air pollution became especially pronounced in the 19th century, with the rapid expansion of cities and the advent of the Industrial Revolution. This period witnessed a surge in domestic fires and factory furnaces, leading to a significant increase in polluted emissions.

The 19th century saw the emergence of the fog-laden atmosphere of London, vividly depicted in the writings of Charles Dickens and Arthur Conan Doyle. These dense fogs, known as "pea-soupers", were a hallmark of London by the 19th century and had been an issue since at least the 13th century due to the burning of coal. The situation deteriorated as the city expanded, and complaints about smoke and pollution increased in the 1600s, prompting ineffective legislation under King James I to restrict coal burning.

The 19th-century smog episodes in London and other cities had devastating consequences, causing numerous deaths and exacerbating respiratory issues. The combination of industrial pollution and weather conditions, particularly cold weather and windless or stagnant air, led to the formation of thick smog that blanketed the city. The smog reduced visibility, disrupted transportation, and penetrated indoor areas, affecting individuals with pre-existing respiratory and cardiovascular problems the most.

The Great Smog of London in 1952, which lasted from December 5 to December 9, is a notable example of the deadly impact of 19th-century smog episodes. The smog was caused by a combination of industrial pollution, the extensive use of coal, and high-pressure weather conditions. It resulted in thousands of deaths, with estimates ranging from 4,000 to 12,000 fatalities, mainly due to respiratory tract infections and lung infections. The long-term effects of the Great Smog included lower intelligence and worsened respiratory health in individuals who were foetuses or infants during the event.

The Great Smog of London served as a pivotal moment in the history of environmentalism, leading to the passage of the Clean Air Act in 1956 and subsequent environmental legislation to address air pollution. While the 19th century marked a significant period for outdoor air pollution, the issue has persisted and evolved, with climate change intensifying the impacts of pollutants and contributing to rising global temperatures, sea levels, and extreme weather events.

20th-century air pollution: continued to be a significant problem

Air pollution has been a recognised threat to human health since the time of Hippocrates, around 400 BC. However, it became a significant problem during the Industrial Revolution, and this issue continued through to the 20th century.

In the 19th century, episodes of "smog" (a combination of smoke and fog) in cities like New York and London resulted in many deaths. This issue persisted and, in 1948, 20 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 this issue by setting limits on the discharge of air pollutants from industrial facilities and motor vehicles, and by tackling acid rain and ozone depletion. Despite these legislative efforts, air pollution remains a pressing issue, with 4.5 million deaths linked to outdoor air pollution in 2019, according to the 2020 State of Global Air report. The report also highlights that China and India, the world's most populous countries, bear the highest burdens of disease.

While the Clean Air Act has helped reduce harmful emissions from transportation, power plants, and manufacturing, air pollution continues to be a significant problem in the 21st century. More than one in three US residents live in counties with unhealthy levels of air pollution, as per the 2023 State of the Air report by the American Lung Association. Climate change is exacerbating this issue, with increased heat intensifying smog and extending the pollen production season, which affects individuals with allergies and asthma.

The World Health Organization (WHO) recognises the urgency of addressing air pollution, with all member states approving resolution A68.8, "Health and the Environment: addressing the health impact of air pollution," at the World Health Assembly in 2015. WHO supports countries in mitigating air pollution and its health risks through evidence-based policies and interventions.

Today: outdoor air pollution is the fourth-largest risk factor for early death

The dangers of air pollution have been recognised since the time of Hippocrates, around 400 BC. However, the problem of outdoor air pollution became particularly significant during the Industrial Revolution, as cities became more populated and industrialised. Since then, air pollution has continued to be a serious issue, with episodes of "smog" in 19th-century cities like New York and London resulting in numerous deaths.

Today, outdoor air pollution is the fourth-largest risk factor for early death worldwide. According to the 2020 State of Global Air report, 4.5 million deaths were linked to outdoor air pollution in 2019, with an additional 2.2 million caused by indoor air pollution. These numbers highlight the urgency of addressing air pollution to protect public health.

The World Health Organization (WHO) has recognised the severity of the problem, with all member states approving resolution A68.8, "Health and the Environment: addressing the health impact of air pollution," at the World Health Assembly in 2015. The latest burden estimates reflect the significant role of air pollution in cardiovascular illness and death, particularly in low- and middle-income countries. Outdoor air pollution disproportionately affects these regions, with 89% of premature deaths occurring in these areas, especially in the WHO South-East Asia and Western Pacific Regions.

Particulate matter (PM) is a common proxy indicator for air pollution, and there is strong evidence of its negative health impacts. The major components of PM include sulfates, nitrates, ammonia, sodium chloride, black carbon, mineral dust, and water. Additionally, greenhouse gases like carbon dioxide and methane contribute to climate change, leading to warmer temperatures, rising sea levels, more extreme weather, and heat-related deaths.

While there have been improvements in reducing global average mortality rates from air pollution, the climate crisis threatens to worsen the problem. For example, smog is intensified by increased heat and ultraviolet radiation, further endangering public health. Strong controls on emissions and clean air legislation are crucial to mitigating the impact of outdoor air pollution on human health and the environment.

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