Air pollution is contamination of the indoor or outdoor environment by any chemical, physical, or biological agent that modifies the natural characteristics of the atmosphere. World Health Organization (WHO) data shows that in 2019 almost all of the global population (99%) breathed air that exceeds WHO guideline limits and contains high levels of pollutants (World Health Organization, a). Air pollution is a complex mixture of solid particles, liquid droplets, and gasses. It can come from many sources, for example: household fuel burning, industrial chimneys, motor vehicles, traffic exhausts, power generation, open burning of waste, agricultural practices, desert dust, forest fires and many other sources (World Health Organization, 2021).
What are some of the sources of air pollution?
Household fuel burning, industrial chimneys, motor vehicles, traffic exhausts, power generation, open burning of waste, agricultural practices, desert dust, forest fires and many other sources.
Air Pollution Health Effects
Ambient (outdoor) air pollution in both cities and rural areas was estimated to cause 4.2 million early deaths worldwide in 2019. The combined effects of ambient and household air pollution are associated with 6.7 million premature deaths annually (World Health Organization, 2022a). Outdoor and indoor air pollution cause respiratory illness and other diseases and are major sources of illnesses and death (World Health Organization, a).
Air Pollution Control
Air pollution is one of the greatest environmental risks to human health. By reducing air pollution levels, countries can reduce the burden of disease from stroke, heart disease, lung cancer, and both chronic and acute respiratory diseases, including asthma. The lower the levels of air pollution, the better the cardiovascular and respiratory health of the population will be, both long and short-term. Most sources of outdoor air pollution are well beyond the control of individuals and demand joint action by local, national, and regional-level policymakers working in sectors like transport, energy, waste management, urban planning, and agriculture (World Health Organization, 2022a).
There are many examples of successful policies that reduce air pollution.
For Industry
Clean technologies that reduce industrial smokestack emissions; improved management of urban and agricultural waste, including capture of methane gas released from waste sites as an alternative to burning (World Health Organization, 2022a).
For Energy
Ensuring access to affordable, clean household energy solutions for cooking, heating, and lighting (World Health Organization, 2022a).
For Transportation
Shifting to clean modes of power generation; focusing on rapid urban transit, walking, and cycling networks in cities as well as rail interurban freight and passenger travel; shifting to cleaner heavy-duty diesel vehicles and low-emissions vehicles and fuels, including fuels with reduced sulfur content (World Health Organization, 2022a).
For Urban Planning
Improving the energy efficiency of buildings and making cities greener and more compact, and thus energy efficient (World Health Organization, 2022a).
For Power Generation
Increased use of low-emissions fuels and renewable power sources that will not combust (like solar, wind, or hydropower); co-generation of heat and power; and distributed energy generation (for example, mini-grids and rooftop solar power generation) (World Health Organization, 2022a).
For City and Agricultural Waste Management
Strategies for waste reduction, separation, recycling, and reusing; as well as improved methods of biological waste management such as anaerobic waste digestion to produce biogas, are practical, low-cost alternatives to the open burning of solid waste. Where burning is not avoidable, then combustion technologies with strict emission controls are critical (World Health Organization, 2022a).
What are some successful policies for controlling air pollution?
INDUSTRY: Clean technologies that reduce industrial smokestack emissions; improved management of urban and agricultural waste, including capture of methane gas released emitted from waste sites as an alternative to burning.
ENERGY: Ensuring access to affordable, clean household energy solutions for cooking, heating, and lighting.
TRANSPORTATION: Shifting to clean modes of power generation; focusing on prioritizing rapid urban transit, walking, and cycling networks in cities as well as rail interurban freight and passenger travel; shifting to cleaner heavy-duty diesel vehicles and low-emissions vehicles and fuels, including fuels with reduced sulfur content.
URBAN PLANNING: Improving the energy efficiency of buildings and making cities greener and more compact, and thus energy efficient.
POWER GENERATION: Increased use of low-emissions fuels and renewable combustion-free power sources that will not combust (like solar, wind, or hydropower); co-generation of heat and power; and distributed energy generation (e.g., small and roof rooftop solar power generation).
CITY MUNICIPAL AND AGRICULTURAL WASTE: Strategies for waste reduction, separation, recycling, and reuse or reprocessing; as well as improved methods of living biological waste management such as anaerobic waste digestion to produce biogas, are practical, low-cost alternatives to the open burning incineration of solid waste. Where burning incineration is not avoidable, then burning combustion technologies with strict emission controls are critical.
Ambient Air Contaminants
Pollutants of major public health concern include ozone (O3), particulate matter (PM), carbon monoxide (CO), nitrogen dioxide (NO2) and Sulfur Dioxide (SO2) (World Health Organization, b). The WHO has global air quality guidelines for these air pollutants. In the United States, these same pollutants are regulated by the Environmental Protection Agency (EPA) and are called Criteria Pollutants.
Ozone
Basic Information
Ozone is found in both the Earth's upper atmosphere (the stratosphere) and lower atmosphere (the troposphere). Depending on where it is in the atmosphere, ozone affects life on Earth in either good or bad ways. Stratospheric ozone is formed naturally through the interaction of solar ultraviolet (UV) radiation with molecular oxygen (O2). The "ozone layer," approximately 6–30 miles above the Earth's surface, reduces the amount of harmful UV radiation reaching the Earth's surface. Tropospheric or ground-level ozone is one of the major components of photochemical smog. It is formed by the reaction with sunlight (photochemical reaction) of pollutants such as nitrogen oxides (NOx) from vehicle and industry emissions and volatile organic compounds (VOC’s) released by vehicles, solvents, and industry. These reactions have commonly been viewed as depending upon the presence of heat and sunlight, resulting in higher ambient ozone concentrations in summer months. Ozone is most likely to reach unhealthy levels on hot sunny days in urban environments but can still reach high levels during colder months. Ozone can also be transported long distances by wind, so even rural areas can experience high ozone levels (Environmental Protection Agency, b).
Characteristics
Ozone (O3) is a highly reactive gas made up of three oxygen atoms. It is both a natural and a man-made product that occurs in the stratosphere and the troposphere (Environmental Protection Agency, b).
Health Effects
Ozone in the air we breathe can harm our health, especially on hot sunny days when ozone can reach unhealthy levels. People at greatest risk of harm from breathing air containing ozone include people with asthma, children, older adults, and people who are active outdoors, especially outdoor workers. Depending on the level of exposure, ozone can cause coughing and sore or scratchy throat, make it more difficult to breathe deeply, and cause pain when taking a deep breath, inflame and damage the airways, make the lungs more susceptible to infection, worsen lung diseases such as asthma, emphysema, and chronic bronchitis, and increase the frequency of asthma attacks. Some of these effects have been found even in healthy people, but effects can be more serious in people with lung diseases such as asthma. They may lead to increased school absences, medication use, visits to doctors and emergency rooms, and hospital admissions (Environmental Protection Agency, 2022c).
Controls
At a community level, there are several effective ozone controls. They include vapor recovery nozzles at the gasoline pumps to reduce refueling emissions; cleaner burning gasoline reformulated to reduce VOC’s, NOx, and other pollutants; enhanced vehicle inspection programs in states; strict NOx emission limits for power plants and industrial combustion sources; and strict limitations on when the solvent is used in factories (Environmental Protection Agency, a). On an individual level you can conserve electricity and set your air conditioner at a higher temperature, choose a cleaner drive, share a ride to work or use public transportation, bicycle or walk to errands when possible, refuel cars and trucks after dark, combine errands and reduce trips, limit engine idling, use household, and garden chemicals in ways that keep evaporation to a minimum, or try to delay using them when poor air quality is forecast (AirNow,).
Particulate Matter
Basic Information
Particulate matter (PM) is a common indicator for air pollution. The major components of PM are sulfate, nitrates, ammonia, sodium chloride, black carbon, mineral dust, and water (World Health Organization, 2022a). It consists of a complex mixture of solid and liquid particles of organic and inorganic substances suspended in the air. Different sources can lead to different mixtures of air pollution. For example, an urban city near the sea can have particulate matter consisting of sea salt, road dust, and smoke from diesel engines. In contrast, a rural area near a forest may have particulate matter consisting of soil, smoke from cookstoves, and forest fires (World Health Organization, 2021). Other sources include construction sites, unpaved roads, agricultural fields, smokestacks, or fires. Vehicle exhaust can cause particulate matter as well as rubber coming off the tires, so PM is often found near areas with high traffic.
Fine particles are also the main cause of reduced visibility (haze). These particles come in many sizes and shapes and can be made up of hundreds of different chemicals. PM10 and PM2.5 are the two categories for particulate pollution. PM10 includes inhalable particles, with diameters that are generally 10 micrometers and smaller; and PM2.5 includes fine inhalable particles, with diameters that are generally 2.5 micrometers and smaller (Environmental Protection Agency, 2022f).
Characteristics
PM is a mixture of solid particles and liquid droplets found in the air. Some particles, such as dust, dirt, soot, or smoke, are large or dark enough to be seen with the naked eye. Others are so small they can only be detected using an electron microscope. To give an idea of the size of the particulates, the average human hair is about 70 micrometers in diameter, so it is 30 times larger than PM2.5 (Environmental Protection Agency, 2022f).
Health Effects
The size of particles is directly linked to their potential for causing health problems. Small particles less than 10 micrometers in diameter give the greatest problems, because they can get deep into your lungs, and some may even get into your bloodstream. Of these, particles less than 2.5 micrometers in diameter, also known as fine particles or PM2.5, give the greatest risk to health. Exposure to such particles can affect both your lungs and your heart. Numerous scientific studies have linked particle pollution exposure to a variety of problems, including early death in people with heart or lung disease, non-deadly heart attacks, irregular heartbeat, worsened asthma, decreased lung function, and increased respiratory symptoms, such as irritation of the airways, coughing, or difficulty breathing. People with heart or lung diseases, children, and older adults are the most likely to be affected by particle pollution exposure (Environmental Protection Agency, 2022f).
Controls
At a community level, PM can be controlled by vehicle emission standards and exhaust testing, limitations on residential wood burning, requirements for controlling dust at agricultural and construction sites, and controlling dust on unpaved roads.
On an individual level you can stay indoors with filtered air. If you cannot buy filters for your entire home, create a clean room for sleeping. Avoid using anything that burns, such as wood fireplaces, gas logs, and even candles or incense. Don’t vacuum unless your vacuum has a HEPA filter, and don’t smoke indoors (Airnow,).
Carbon Monoxide
Basic Information
Carbon Monoxide (CO) is released when something is burned and is the result of incomplete burning. The greatest sources of CO to outdoor air are cars, trucks, and other vehicles or machinery that burn fossil fuels (World Health Organization, 2022a). Since indoor exposures to CO are more of a concern than outdoor levels, additional information will be provided in the section on indoor Carbon Monoxide.
Characteristics
Carbon monoxide is a colorless, odorless and tasteless gas (World Health Organization, 2022a).
Health Effects
It can be harmful when inhaled in large amounts. Breathing air with a high concentration of CO reduces the amount of oxygen that can be transported in the bloodstream to critical organs like the heart and brain. At very high levels, which are possible indoors or in other enclosed environments, CO can cause dizziness, confusion, unconsciousness, and death. Very high levels of CO are not likely to occur outdoors. However, when CO levels are increased outdoors, they can be of particular concern for people with some types of heart disease. These people already have a reduced ability for getting oxygenated blood to their hearts in situations where the heart needs more oxygen than usual. They are less able to defend against the effects of CO when exercising or under increased stress. In these situations, short-term exposure to increased levels of CO may result in reduced oxygen to the heart accompanied by chest pain also known as angina (Environmental Protection Agency, 2022a; World Health Organization, 2022a)).
Controls
Make sure combustion equipment is maintained and properly adjusted. The use of vehicles should be carefully managed adjacent to buildings. Additional ventilation can be used as a temporary control when high levels of CO are expected for short periods of time (Environmental Protection Agency, 2022b).
Nitrogen Oxides
Basic Information
Nitrogen Dioxide (NO2) is part of a group of highly reactive gasses known as oxides of nitrogen or nitrogen oxides (NOx). Other nitrogen oxides include nitrous acid and nitric acid. NO2 is used as the indicator for the larger group of nitrogen oxides. NO2 primarily gets in the air from the burning of fuel. The major sources of anthropogenic emissions of NO2 are fuel burning processes such as emissions from cars, trucks, and buses, power plants, heating, and power generation (Environmental Protection Agency, 2022d).
Characteristics
Nitrogen Oxides (NOx) are highly reactive, often appearing as a brownish gas (Environmental Protection Agency, 2022e). Nitrogen oxides react with water and oxygen to create acid rain (Environmental Protection Agency, 2022d)(Environmental Protection Agency, 2022h).
Health Effects
Breathing air with a high concentration of NO2 can irritate airways in the human respiratory system. Such exposures over short periods can worsen respiratory diseases, particularly asthma, leading to respiratory symptoms (such as coughing, wheezing, or difficulty breathing), hospital admissions, and visits to emergency rooms. Longer exposures to increased concentrations of NO2 may contribute to the development of asthma and potentially increase susceptibility to respiratory infections. People with asthma, as well as children and the elderly, are generally at greater risk for the health effects of NO2(Environmental Protection Agency, 2022d).
Controls
NOx primarily gets in the air from the burning of fuel. Controls include the use of catalytic converters for all vehicles and regular emissions testing of vehicles.
Sulfur Dioxide
Basic Information
Sulfur Dioxide (SO₂) is used as the indicator for the larger group of gaseous sulfur oxides (SOx). SOx can react with other compounds in the atmosphere to form small particles. These particles contribute to particulate matter pollution. Other gaseous SOx (such as SO3) are found in the atmosphere at concentrations much lower than SO₂. The largest sources of SO₂ emissions are from fossil fuel burning at power plants and other industrial facilities. Smaller sources of SO₂ emissions include industrial processes such as extracting metal from ore; natural sources such as volcanoes; and trains, ships, and other vehicles and heavy equipment that burn fuel with a high sulfur content (Environmental Protection Agency, 2022g). When SO₂ combines with water, it forms sulfuric acid; this is the main component of acid rain which can affect aquatic environments(Environmental Protection Agency, 2022h). At high concentrations, gaseous SOx can harm trees and plants by damaging leaves and decreasing growth. SO₂ and other sulfur oxides can react with other compounds in the atmosphere to form fine particles that reduce visibility (haze) (Environmental Protection Agency, 2022g).
Characteristics
SO₂ is a colorless gas with a characteristic, irritating, pungent scent (CDC, 2019). It is a liquid when under pressure (ATSDR, 2014). SO₂ reacts with water to create acid rain (Environmental Protection Agency, 2022h).
Health Effects
Short-term exposures to SO2 can harm the human respiratory system and make breathing difficult. People with asthma, particularly children, are sensitive to the effects of SO2 (Environmental Protection Agency, 2022g).
Long-term exposure to persistent levels of sulfur dioxide can affect your health. Lung function changes were seen in some workers exposed to low levels of sulfur dioxide for 20 years or more. Exposure to very high levels of sulfur dioxide can be life threatening. Children who live in or near heavily industrialized areas where sulfur dioxide occurs may have trouble breathing, changes in the ability to breathe deeply, and burning of the nose and throat (ATSDR, 2014). Exposure to SO2 is associated with asthma hospital admissions and emergency room visits (World Health Organization, b).
Controls
Since the majority of SO2 emissions come from fossil fuel burning at power plants the main control is to affix efficient SO2 scrubbers to the exhaust stacks at these power plants.
Indoor Air Quality
Household or Indoor air pollution was responsible for an estimated 3.2 million deaths per year in 2020, including over 237,000 deaths of children under the age of five. Exposure to indoor or household air pollutants can lead to a wide range of adverse health conditions ranging from eye conditions to respiratory illnesses and cancer. Almost half of all deaths due to lower respiratory infection among children under five years of age are caused by inhaling particulate matter (soot) from household air pollution (World Health Organization, 2022b). There are many sources of indoor or household air pollution. This course will look at three of the most important: cooking exhaust, carbon monoxide, and mold.
Cooking Exhaust
Basic Information
Worldwide, around 2.4 billion people still cook using solid fuels (such as wood, crop waste, charcoal, coal and dung) and kerosene in open fires and inefficient stoves. In poorly ventilated dwellings, indoor smoke can have levels of fine particles 100 times higher than acceptable. Exposure is particularly high among women and children, who spend the most time laboring over household chores such as cooking and collecting firewood and spend more time exposed to harmful smoke from polluting stoves and fuels (World Health Organization, 2022b).
Health Effects
Household air pollution exposure leads to noncommunicable diseases including stroke, ischemic heart disease, chronic obstructive pulmonary disease (COPD), and lung cancer. Particulate matter and other pollutants in household air pollution inflame the airways and lungs, impair immune response, and reduce the oxygen-carrying capacity of the blood. (World Health Organization, 2022b).
Controls
Implement strategies to increase the adoption of clean household energy such as solar, electricity, biogas, liquefied petroleum gas (LPG), natural gas, and alcohol fuels (World Health Organization, 2022b). Improve ventilation and housing design by installing chimneys or hoods. Include policies that provide financial support to purchase cleaner technologies and fuels.
Educational campaigns using radio ads, flyers, billboards, posters, or other mediums could be used to highlight the benefits of clean fuel use and the negative impacts of polluting fuels (World Health Organization, b).
Indoor Carbon Monoxide
Basic Information
Carbon monoxide is created when there is incomplete combustion; there is therefore a possibility for CO exposure anywhere in your building or house where there is a flame. Items in your home that could generate CO include unvented kerosene and gas space heaters, leaking chimneys and furnaces, gasoline powered equipment, auto, truck, or bus exhaust from attached garages, nearby roads, or parking areas, or appliances such as gas water heaters, stoves, washers, and dryers (Environmental Protection Agency, 2022b).
Characteristics
Carbon monoxide is a colorless, and harmful gas with no scent. Because it is impossible to see, taste, or smell it, CO can kill you before you are aware it is in your home (Environmental Protection Agency, 2022b).
Health Effects
At low concentrations, symptoms include fatigue in healthy people and chest pain in people with heart disease. At moderate concentrations symptoms include angina, impaired vision, and reduced brain function. At higher concentrations, symptoms include impaired vision and coordination, headaches, dizziness, confusion, nausea, and it is deadly at very high concentrations. Acute effects are due to the formation of carboxyhemoglobin in the blood, which inhibits oxygen intake and can lead to death (Environmental Protection Agency, 2022b).
Controls
There are a variety of controls that can be implemented in your building or house. Those controls include keeping gas appliances properly adjusted, replacing unvented space heaters with vented ones, using proper fuel in kerosene space heaters, installing an exhaust fan vented to outdoors over gas stoves, choosing properly sized wood stoves, and not idling the car inside the garage (Environmental Protection Agency, 2022b).
Mold
Basic Information
Mold is very common in buildings and homes. Mold can enter your home through open doorways, windows, vents, and heating and air conditioning systems. Mold in the air outside can also attach itself to clothing, shoes, and pets and be carried indoors. When mold spores drop on places where there is excessive moisture, such as where leakage may have occurred in roofs, pipes, walls, plant pots, or where there has been flooding, they will grow. Many building materials provide suitable nutrients that encourage mold to grow. Some of the most common indoor molds are Cladosporium, Penicillium, and Aspergillus (CDC, 2022).
Health Effects
Exposure to damp and moldy environments may cause a variety of health effects, or none at all. Some people are sensitive to molds. For these people, exposure to molds can lead to symptoms such as stuffy nose, wheezing, and red or itchy eyes or skin. Some people, such as those with allergies to molds or with asthma, may have more intense reactions. Severe reactions may occur among workers exposed to large amounts of molds in occupational settings, such as farmers working around moldy hay. Severe reactions may include fever and shortness of breath. In 2004, the Institute of Medicine (IOM) found there was sufficient evidence to link indoor exposure to mold with upper respiratory tract symptoms, cough, and wheeze in otherwise healthy people; with asthma symptoms in people with asthma; and with hypersensitivity pneumonitis in individuals who are prone. People with allergies may be more sensitive to molds. People with immune suppression or underlying lung disease are more inclined to fungal infections. Individuals with chronic respiratory disease may have trouble breathing. Individuals with immunosuppression are at increased risk for infection from molds (CDC, 2022).
Controls
Inspect buildings or residences for evidence of water damage and visible mold as part of routine building maintenance. Correct conditions causing mold growth (for example: water leaks, condensation, infiltration, or flooding) to prevent mold growth. Inside your home you can control mold growth by controlling humidity levels, quickly fixing leaky roofs, windows, and pipes, thoroughly cleaning and drying after flooding, and ventilating shower, laundry, and cooking areas. Clean areas that have mold. Hire a professional to remove mold if you do not feel confident around mold (CDC, 2022).
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