Pollution Levels: A Drop For The Better?

Air pollution is a serious issue that poses a significant risk to human health. While there have been efforts to improve air quality and reduce pollution, the success of these attempts is varied. For example, during the COVID-19 pandemic, countries like China, Italy, and the United States saw a significant drop in pollution levels due to reduced traffic and travel. However, in the years leading up to 2025, nearly half of Americans were reported to be breathing in unsafe levels of air pollutants, with climate change-driven heatwaves and wildfires contributing to increased ozone levels. This complex issue requires ongoing attention and action to ensure the health and well-being of people worldwide.

Air pollution's impact on health

Air pollution is defined as the presence of one or more contaminants in the atmosphere, such as dust, fumes, gas, mist, odour, smoke or vapour, in quantities and durations that can be harmful to human health. The main pathway of exposure from air pollution is through the respiratory tract. However, due to their small size, some air pollutants can penetrate the bloodstream via the lungs and circulate throughout the entire body, leading to systemic inflammation and carcinogenicity.

Air pollution is now the biggest risk factor for premature death, causing more than six million premature deaths each year. Research suggests that long-term exposure to some pollutants increases the risk of emphysema more than smoking a pack of cigarettes a day. In addition, recent studies have shown that air pollution can also impact mental health, worker productivity, and stock market performance.

The health impacts of air pollution depend on the types and concentrations of the pollutants in the air. Fine particulate matter, for example, is a common and critical pollutant of both ambient and household air pollution, leading to negative health impacts. Particulate matter (PM) is made up of small airborne particles like dust, soot, and liquid droplets. The majority of PM in urban areas comes from burning fossil fuels, automobiles, non-road equipment, and industrial facilities. Coarse particulate matter (PM10) is known to cause nasal and upper respiratory tract health problems. Fine particles (PM2.5) penetrate deeper into the lungs and can cause heart attacks, strokes, asthma, bronchitis, and premature death from heart ailments, lung disease, and cancer.

In addition to particulate matter, other pollutants with strong evidence of adverse health effects include carbon monoxide (CO), ozone (O3), nitrogen dioxide (NO2), and sulphur dioxide (SO2). Ozone air pollution can irritate the lungs and make breathing difficult. Sulphur dioxide causes eye irritation, worsens asthma, increases susceptibility to respiratory infections, and impacts the cardiovascular system. Exposure to high levels of air pollution can lead to reduced lung function, respiratory infections, and aggravated asthma from short-term exposure. Long-term exposure to fine particulate matter increases the risk of diseases with longer onsets, such as stroke, heart disease, chronic obstructive pulmonary disease, and cancer. Maternal exposure to air pollution is also associated with adverse birth outcomes, such as low birth weight, pre-term birth, and small gestational age births.

The Clean Air Act

The Act defines the Environmental Protection Agency's (EPA) responsibilities for protecting and improving the nation's air quality and the stratospheric ozone layer. The EPA develops extensive administrative regulations and policies to carry out the law's mandates, in coordination with state, local, and tribal governments.

One of the goals of the CAA was to set and achieve National Ambient Air Quality Standards (NAAQS) in every state by 1975 to address the health and welfare risks posed by widespread air pollutants. The Act also established a risk-based program for emissions of hazardous air pollutants, which was revised in 1990 to require the issuance of technology-based standards for major sources, such as power plants and industrial facilities.

The 1990 amendments to the CAA also addressed four major threats to the environment and public health: acid rain, urban air pollution, toxic air emissions, and stratospheric ozone depletion. The Acid Rain Program (ARP) was established as the first cap-and-trade emissions program in the US, targeting sulfur dioxide and nitrogen oxide emissions from fossil fuel power plants.

Since the implementation of the CAA, there has been significant progress in reducing air pollution in the US. Between 1970 and 2023, total emissions of the six principal air pollutants dropped by 78%, and since 1990, there has been an approximate 50% decline in emissions of key air pollutants. The CAA has been credited with saving trillions of dollars and thousands of lives each year, preventing serious health issues caused by air pollution.

Sources of pollution

Point-Source Pollution

Point-source pollution is primarily associated with industrial activities and human-generated waste. Some common sources include:

• Factories and power plants: These facilities emit pollutants such as carbon monoxide, heavy metals, sulfur dioxide, nitrogen dioxide, and particulate matter into the air. They also discharge wastewater containing harmful chemicals into nearby water bodies.
• Oil refineries: Refineries and other oil/product handling facilities contribute to pollution through leaks and spills from storage tanks and pipelines.
• Municipal wastewater treatment plants: These plants can introduce nutrients and harmful microbes into waterways, leading to issues such as algae blooms.
• Large farms with livestock: Also known as concentrated animal feeding operations (CAFOs), these farms can release untreated animal waste into nearby water bodies, causing water pollution.

Nonpoint-Source Pollution

Nonpoint-source pollution is more diffuse and challenging to manage. Some examples include:

• Urban runoff: Rainwater washes away pollutants from streets, roofs, and other hard surfaces, carrying them into nearby water bodies. This includes oil, particles from tires, waste, trash, and chemicals.
• Agricultural activities: Fertilizers, pesticides, and other chemicals used in agriculture can be washed into rivers, lakes, and streams, impacting aquatic life and water quality.
• Acid rain: Formed by the combination of sulfur dioxide, nitrogen oxides, and water in the atmosphere, acid rain results from pollutants emitted by factories and power plants.
• Natural sources: Volcanic eruptions, wildfires, and wind-blown dust are natural sources of pollution that can have significant impacts on air quality.

Mobile and Stationary Sources

Another way to categorize pollution sources is by dividing them into mobile and stationary categories. Mobile sources include vehicles such as cars, buses, planes, trucks, and trains. These contribute significantly to air pollution, particularly in urban areas, by emitting pollutants through their exhaust systems. Stationary sources, on the other hand, include fixed facilities like power plants, oil refineries, industrial facilities, and factories. These sources emit pollutants from a single location and are also known as point sources.

Climate change and pollution

Climate change can directly impact air quality, especially in regions susceptible to temperature and precipitation changes. Hot, sunny days can increase ground-level ozone, a greenhouse gas that traps heat in the atmosphere, further contributing to climate change. Climate change-induced droughts can increase particulate matter in the air, and wildfires can release smoke that reduces air quality and harms human health.

In addition, climate change can worsen indoor air quality. Increased outdoor pollutants can enter buildings and cause higher indoor exposures. Climate change-related precipitation and storms can create damp indoor environments, fostering the growth of harmful pollutants like mold, dust mites, and bacteria. These indoor air pollutants have been linked to adverse health effects, including heart disease, respiratory issues, and cancer.

While efforts to reduce air pollution can positively impact climate change, it is important to recognize that climate change can also exacerbate pollution levels. Extreme weather events associated with climate change, such as flooding and storm surges, can damage buildings, creating conditions for harmful pollutants to thrive. Additionally, longer summers and increased temperatures can worsen ground-level ozone and particulate matter pollution.

Addressing air pollution and climate change together is crucial for improving public health, protecting ecosystems, and mitigating global warming. Lowering air pollution levels can lead to better cardiovascular and respiratory health, while also reducing emissions of short-lived climate pollutants like methane and black carbon, which have a significant global warming potential.

Despite challenges, there is progress in reducing air pollution. Between 1970 and 2023, total emissions of the six principal air pollutants in the US dropped by 78%, and CO2 emissions have decreased overall since 2007. Regulatory initiatives, partnership programs, and individual actions can further reduce air pollutants and greenhouse gases, improving both air quality and climate change outcomes.

Pollution levels in cities

Air pollution is a pressing issue that has plagued many cities worldwide. While there have been efforts and progress made in reducing pollution levels, it remains a significant concern, especially in urban areas.

In the United States, air pollution has been a long-standing challenge, with nearly half of the population living in areas with unhealthy air pollution levels. According to the American Lung Association's (ALA) 2025 annual report, air quality has deteriorated compared to the previous year, with 25 million more people living in areas with poor air quality. This increase is attributed mainly to communities on the East Coast affected by smoke from Canadian wildfires in 2023.

Some of the most polluted cities in the US include Los Angeles-Long Beach, California, which ranks highest in ozone levels and among the top 10 in particle pollution. Bakersfield-Delano, California, also experiences severe particle pollution, with high daily spikes and annual averages. Other cities like Phoenix, Arizona, and Dallas, Texas, are in the top 10 for smog-heavy air. People of color and minority communities are disproportionately affected by air pollution, with higher rates of respiratory issues and other health complications.

However, it's important to recognize that air pollution levels can vary widely across different regions. For instance, California has some of the worst air quality in the country, while cities like Augusta-Richmond County (Georgia/South Carolina), Casper (Wyoming), and Asheville-Waynesville-Brevard (North Carolina) are listed among the cleanest areas in terms of ozone and particle pollution.

To address air pollution, various policies and regulations have been implemented. The Clean Air Act, passed in 1963, contributed to significant reductions in air pollution across the country, with an 80% decrease in pollution levels since its implementation. Additionally, federal and state regulations, technological advancements, and national programs by the Environmental Protection Agency (EPA) have helped improve air quality over the years.

Despite these efforts, air pollution continues to be a pressing issue, and further actions are necessary to achieve substantial and sustained improvements in air quality, particularly in highly populated urban areas.

Frequently asked questions