Air Pollution: Understanding Different Types

Air pollution is a pressing issue that poses significant risks to human health and the environment. It encompasses a range of pollutants, including particle pollution, ground-level ozone, carbon monoxide, lead, nitrogen oxides, and sulfur oxides. These pollutants can have detrimental effects on respiratory and cardiovascular health, leading to conditions such as asthma, lung disease, and even lung cancer. With outdoor air quality still facing challenges, it is crucial to understand the types of air pollution, their sources, and their impacts to implement effective measures for reducing emissions and mitigating their harmful effects on people and the planet.

Natural sources of air pollution

Volcanoes, for instance, can spew massive amounts of sulphur dioxide into the atmosphere. In the past, volcanoes were the main source of atmospheric sulphur dioxide. Wildfires are another natural source of air pollution, emitting smoke and harmful gases, including particulate matter, carbon monoxide, and nitrogen dioxide.

Some natural sources of air pollution are also related to human activity, such as agricultural practices. Agriculture can pollute the air through emissions of ammonia gas and the application of pesticides, herbicides, and insecticides, which contain toxic volatile organic compounds. Livestock, such as cows and sheep, also release large amounts of methane, a significant greenhouse gas, through belching and flatulence.

Burning fossil fuels

The combustion of fossil fuels also emits harmful pollutants, such as particulate matter (PM), nitrogen dioxide (NO2), and carbon monoxide (CO). PM refers to inhalable particles composed of sulphate, nitrates, ammonia, sodium chloride, black carbon, mineral dust, or water. These particles vary in size, with PM2.5 and PM10 being the most common in regulatory frameworks due to their health implications. PM2.5, with a diameter of up to 2.5 microns, is particularly dangerous as it can linger in the air, be easily inhaled, and penetrate deep into the lungs, causing respiratory and cardiovascular issues. Burning fossil fuels, especially coal, gasoline, and diesel, is a significant contributor to PM2.5 pollution, including soot production.

Nitrogen dioxide (NO2), a reddish-brown gas, is another pollutant released during the high-temperature combustion of fossil fuels for heating, transportation, industry, and power generation. NO2 irritates airways and exacerbates respiratory diseases. It is also a precursor to ground-level ozone (O3), a major component of smog. Ozone is formed through photochemical reactions with volatile organic compounds, carbon monoxide, and nitrogen oxides emitted from vehicles and industry. High levels of ozone are typically observed during sunny weather and can cause breathing difficulties, trigger asthma, reduce lung function, and lead to lung disease.

Carbon monoxide (CO), a colourless and odourless gas, is produced by the incomplete combustion of carbonaceous fuels, including wood and petrol. It poses significant health risks, especially when inhaled, as it can reduce the blood's ability to carry oxygen, leading to serious health issues, particularly in vulnerable individuals.

The health impacts of burning fossil fuels are significant, with an estimated 8.7 million premature deaths each year attributed to this type of air pollution. Fossil fuel pollution disproportionately affects children, older individuals, low-income communities, and people of colour, particularly those residing in urban areas. The combustion of fossil fuels also contributes to the climate crisis, with global temperature increases already surpassing critical thresholds. Urgent action is needed to transition to renewable energy sources and address the harmful impacts of burning fossil fuels on human health and the environment.

Indoor air pollution

The health effects of indoor air pollution can be severe and range from immediate reactions such as eye, nose, and throat irritation, headaches, dizziness, and fatigue to more serious long-term issues like respiratory diseases, heart disease, and cancer. People with pre-existing medical conditions or specific individual sensitivities may be more susceptible to the adverse effects of indoor air pollutants. It is important to note that symptoms may resemble those of a cold or other viral disease, making it challenging to attribute them directly to indoor air pollution.

To address indoor air pollution, the World Health Organization (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 improve air quality and protect health. Additionally, WHO offers strategies for transitioning to cleaner household fuels and technologies, and maintains a global household energy database to monitor progress.

Reducing exposure to indoor air pollutants can be achieved through proper ventilation, addressing sources of pollution such as smoke and dust mites, and adopting cleaner alternatives for cooking, space heating, and lighting. It is important to be mindful of the types of fuels and technologies used in the home, as recommended by organizations like WHO, to minimize the health risks associated with indoor air pollution.

Outdoor air pollution

The health effects of outdoor air pollution are well-documented. Exposure to fine particulate matter in the air can cause cardiovascular and respiratory diseases, as well as cancers. The WHO estimates that in 2019, 68% of outdoor air pollution-related premature deaths were due to ischaemic heart disease and stroke, 14% were due to chronic obstructive pulmonary disease, 14% were due to acute lower respiratory infections, and 4% were due to lung cancers. Long-term exposure to air pollution has also been linked to potential impacts on cognitive function.

The mix of pollutants in outdoor air varies in space and time, reflecting the diversity of sources and the influence of atmospheric processes. Commonly measured air pollutants include particulate matter (PM2.5, PM10), nitrogen dioxide, and sulfur dioxide. The concentration of particulate matter is often used as an indicator of overall pollution levels. Other pollutants of concern include carbon monoxide, ground-level ozone, and polycyclic aromatic hydrocarbons (PAHs).

Reducing outdoor air pollution requires concerted action by local, national, and regional policymakers. This includes supporting cleaner transportation, energy-efficient homes, power generation, industry, and better municipal waste management. Individuals can also play a role by advocating for clean air policies and reducing their personal contributions to air pollution, such as by switching to zero-emission transportation and energy sources.

Health risks

Air pollution is the presence of contaminants in the atmosphere, such as dust, fumes, gases, odours, and smoke, in quantities that can be harmful to human health. These pollutants can enter the body through the respiratory tract, leading to inflammation, oxidative stress, immunosuppression, and mutagenicity in cells. This can impact several organs, including the lungs, heart, and brain, and cause various diseases.

One of the most common air pollutants is particulate matter (PM), which refers to inhalable particles composed of sulphate, nitrates, ammonia, sodium chloride, black carbon, mineral dust, or water. PM can vary in size, with PM2.5 and PM10 being the most concerning for health. These fine particles can be derived from combustion processes, such as fuel burning in power generation facilities, industries, or vehicles, and can penetrate deep into the lungs, enter the bloodstream, and cause systemic damage. Exposure to PM2.5 has been linked to increased mortality risk, respiratory infections, reduced lung function, aggravated asthma, and cognitive and emotional problems in children.

Another pollutant, nitrogen dioxide (NO2), is a reddish-brown gas that irritates airways and exacerbates respiratory diseases. It is produced from high-temperature combustion processes in heating, transportation, industry, and power generation. NO2 is also a precursor to ground-level ozone (O3), a major component of smog. Ozone can be generated by household equipment and is more prevalent during sunny weather. Excessive exposure to ozone can cause breathing difficulties, trigger asthma, reduce lung function, and lead to lung disease.

Carbon monoxide (CO), a colourless and odourless gas produced by the incomplete combustion of fuels, is another significant air pollutant. While toxic air pollutants, or hazardous air pollutants (HAPs), are known or suspected to cause cancer and other serious health issues, including reproductive problems and birth defects. Examples of HAPs include benzene, perchloroethylene, and methylene chloride, which are found in gasoline, emitted from dry cleaning facilities, and used as solvents or paint strippers, respectively.

The health effects of air pollution are not evenly distributed, with certain groups being more vulnerable. These include children, pregnant women, older adults, and people with pre-existing chronic conditions, especially heart and lung diseases. Additionally, people of colour and those from low-income communities are disproportionately impacted by air pollution due to systemic racism and socioeconomic factors. Psychosocial stressors, such as poverty, discrimination, and residency status, can further amplify the harmful effects of air pollution on these communities.

Frequently asked questions