Air Pollution: When Does It Start?

Air pollution is the contamination of the indoor or outdoor environment by any chemical, physical, or biological agent that modifies the natural characteristics of the atmosphere. Air pollution is considered to be present when there are substances in the air that are harmful to humans, other living beings, or the environment. The World Health Organization (WHO) reports that air pollution causes nearly seven million deaths worldwide every year, with 99% of people breathing air that exceeds the recommended guideline limits for pollutants.

Indoor air pollution

Air pollution is defined as the contamination of the indoor or outdoor environment by any chemical, physical, or biological agent that modifies the natural characteristics of the atmosphere. According to the World Health Organization (WHO), indoor and outdoor air pollution is responsible for nearly seven million deaths worldwide each year. Indoor air pollution, also known as household air pollution, is caused by a variety of sources and has significant health impacts.

One of the primary sources of indoor air pollution is the use of inefficient and polluting fuels and technologies in the home. This includes the use of open fires or simple stoves fuelled by kerosene, biomass (such as wood, animal dung, and crop waste), and coal for cooking and heating. Around 2.1 billion people worldwide rely on these polluting fuels, and the resulting indoor air pollution has severe health consequences, particularly for women and children who spend the most time near the domestic hearth. Exposure to indoor air pollution has been linked to non-communicable diseases, including stroke, heart disease, chronic obstructive pulmonary disease (COPD), and lung cancer.

Another source of indoor air pollution is the use of gas stoves and heating systems, which can emit pollutants such as nitrogen dioxide (NO2), benzene, and carbon monoxide. Inadequate ventilation can further increase indoor pollutant levels by not properly diluting emissions and removing pollutants from the indoor environment. High temperature and humidity levels can also contribute to higher concentrations of certain pollutants.

Building materials, household cleaners, and biological pollutants such as dust mites, pet dander, and mould are additional sources of indoor air pollution. These pollutants can trigger asthma and cause irritation to the eyes, nose, and throat, as well as headaches, dizziness, and fatigue.

To address indoor air pollution, the WHO has developed guidelines for indoor air quality and household fuel combustion. These guidelines provide recommendations on the types of clean fuels and technologies that can be used to protect health and reduce exposure to harmful pollutants. Additionally, strategies such as improving ventilation, controlling moisture, and maintaining a smoke-free environment can help improve indoor air quality and mitigate the health risks associated with indoor air pollution.

Outdoor air pollution

Particulate matter (PM) is another important indicator of air pollution. It includes sulfates, nitrates, ammonia, sodium chloride, black carbon, mineral dust, and water. Exposure to particulate matter has been linked to negative health consequences. Soot, a type of particulate matter, consists of tiny particles of chemicals, soil, smoke, dust, or allergens that are carried in the air.

Smog, which is formed when emissions from combusting fossil fuels react with sunlight, is another common air pollutant. It can irritate the eyes and throat and damage the lungs, especially in children, the elderly, and those who work or exercise outdoors. Ground-level ozone, a key component of smog, is formed through chemical reactions involving nitrogen dioxide and volatile organic compounds, such as gasoline vapors.

To address outdoor air pollution, various successful policies and interventions have been implemented. These include the promotion of clean technologies in industries, improved waste management practices, access to affordable clean household energy solutions, and the adoption of cleaner modes of power generation and transportation.

Particulate matter

The health effects of particulate matter pollution have been recognized since the twentieth century. One notable incident occurred in 1930 when sulfur dioxide from factory emissions mixed with fog over the Meuse Valley in Belgium, leading to acute pulmonary symptoms and several deaths. Another incident in London in 1952, known as the Great Smog, resulted in thousands of excess deaths and brought the lethality of air pollution to the world's attention.

Today, particulate matter pollution continues to be a significant concern for human health. The World Health Organization estimates that PM air pollution contributes to approximately 800,000 premature deaths each year, making it the 13th leading cause of mortality worldwide. Long-term exposure to fine particles has been linked to increased mortality from heart disease, chronic bronchitis, reduced lung function, and lung cancer. Sensitive groups such as people with heart and breathing problems, pregnant women, children, and older adults are particularly vulnerable to the effects of particulate matter pollution.

To protect public health, regulatory efforts have been implemented to address particulate matter pollution. In the United States, the Environmental Protection Agency (EPA) has designated PM as a "'criteria'" pollutant, indicating that its concentration in the atmosphere is useful for assessing overall air quality. The EPA has also set standards for fine particle pollution (PM2.5) to improve air quality and reduce health risks associated with exposure to particulate matter.

Pollutants from industry

Industrial pollution refers to pollution that originates directly from industry. After the Industrial Revolution, the proliferation of factories and industries led to increased smoke emissions into the air, as well as pollution of water and land. This pollution has had detrimental effects on both human health and the environment.

There are various types of pollutants emitted by industrial processes. Sulfides, for example, are released during wastewater treatment and petrochemical processing and are known for their strong odour even at low concentrations. To remove these sulfides, techniques such as wet scrubbing with packed towers and alkaline (NaOH) scrubbing are employed. Volatile organic compounds (VOCs) are another type of pollutant that is not easily soluble in water or reactive with standard aqueous chemical solutions. Packed towers are generally effective for removing reactive inorganic compounds, while sieve tray towers and eductor venturis are used for specific applications.

The Clean Air Act, established in 1963 in the United States, tasked the Environmental Protection Agency with developing and enforcing regulations to protect citizens from airborne pollutants. Amendments to this Act have since addressed issues like ozone depletion and acid rain. The Clean Water Act, introduced in 1972, aimed to prevent water pollution and maintain the quality of the nation's waters.

In Los Angeles County, factories and businesses contribute significantly to air pollution, leading to health issues such as irritation, headaches, asthma attacks, and an increased cancer risk for residents in the vicinity. Local agencies like the South Coast Air Quality Management District (SCAQMD) play a crucial role in setting rules and regulations to control the type and amount of pollutants released by industries.

The impact of industrial pollution extends beyond local communities. Ice samples from the Arctic and Antarctic have revealed high levels of pollutants, indicating the far-reaching nature of these emissions. Environmental degradation, wildlife extinction, and global warming are all consequences of industrial pollution, underscoring the urgent need to address and mitigate these issues.

Natural sources of air pollution

Wildfires

Wildfires are one of the largest sources of black carbon, or soot, which is very harmful to human health and the environment. Black carbon can lead to lung and heart disease and premature death. It reduces sunlight, impacts plant ecosystems, and absorbs solar heat, contributing to global warming at a rate up to 1,500 times greater than that of CO2. Wildfire air pollutants can cause a range of adverse health effects, including difficulty breathing, an increased risk of asthma, heart failure, and premature death. While wildfires can be a natural phenomenon, largely human-driven global warming has exacerbated their frequency and intensity.

Volcanoes

Volcanoes emit massive amounts of sulphur dioxide, hydrogen sulfide, radon, sulfuric acid, hydrogen, carbon monoxide, hydrogen chloride, hydrogen fluoride, and helium into the atmosphere. These emissions can increase background pollution levels for years, even in areas far away from the original source.

Livestock

Animals like cows and sheep release large amounts of methane through belching and flatulence. Methane is a colourless gas produced in their stomachs when bacteria break down the food they eat. Livestock is the biggest source of methane worldwide. Methane is the second most important greenhouse gas, which can cause climate change.

Soil and Dust

Soil and dust particles can be picked up by the wind and transported over long distances, causing storms of particulate matter. In dry regions lacking vegetation, such as deserts, high winds can lift sand and dust into the air, creating sandstorms.

Vegetation

Organic compounds from plants can contribute to air pollution. In addition, pollen released by vegetation can cause allergic reactions in some individuals.

While most harmful air pollution is caused by human activity, understanding and addressing the impacts of natural sources of air pollution are crucial for improving air quality and mitigating potential health risks.

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