Generally, air quality can be either ‘good’ or ‘poor’.
According to the AQI standard for air quality assessment, good air quality is represented by AQI numbers ranging from 0-50 [7], and is indicative of conditions whereby the air is free of (any significant concentration of) contaminants and does not pose any notable health risks to living organisms.
Good air quality is chromatically represented by the color green.
As the foregoing paragraph implies, good air quality has no effects on health. This is because it does not introduce any contaminants into the respiratory system (lungs, trachea, pharynx, larynx…) or into the blood stream of living organisms, when they inhale as a natural activity for their survival.
From another perspective, it can be said that good air quality has relatively positive effects on health. This is because; poor air quality, on the other hand, is known to have negative effects on health, as we will discuss in the following section of this article.
Effects of Poor Air Quality on Health: What are the Effects of Air Pollution on Health?
The term; ‘Air Pollution’ is an important term with regards to the issue of poor air quality.
Within the context of health effects, the AQI scale of assessment indicates that air quality begins to affect health from the moderate level of contamination/purity.
This gives a scheme in which the health impacts of poor air quality begin to be felt at the moderate, unhealthy, and hazardous levels. The table below shows the AQI assessment scheme, with evaluations on the basis of Air Quality Index values;
Level
Color Code
AQI Range
Interpretation
Description
1
Green
0-50
Good Air Quality
Fairly safe for the ecosystem and environment, poses no notable health implications
2
Yellow
51-100
Moderate Air Quality
Generally safe and acceptable for the ecosystem and environment. However, highly-sensitive organisms may be affected
3
Orange
101-150
Unhealthy for Sensitive Organisms
Affects sensitive groups, less likely to affect the general public
4
Red
151-200
Unhealthy
A great percentage of the living population is likely to be affected. Sensitive groups experience serious health effects
5
Purple
201-300
Very Unhealthy
High risk of health effects exists for all groups (sensitive and relatively-insensitive)
6
Amber/Maroon
301 and above
Hazardous
Emergency health conditions likely to arise. Unsafe for the ecosystem and environment
Health Problems Caused by Poor Air Quality and Air Pollution
Air pollution is the presence of potentially hazardous substances in air.
It can also be described as the release of pollutants- harmful chemical and physical materials -into the air; or the severe contamination of air by these pollutants.
Air pollution is significant when evaluating the link between air quality and health condition, because it generally involves a decrease in the quality of air.
Another way to look at air pollution, is as a degradation of air quality by contaminants (in this case referred to as pollutants) which are mostly released as a result of anthropogenic (human-related) activities and processes.
In any case, air pollution; which is a condition of poor air quality, is associated with some illnesses (especially in humans) some of which are discussed as follows;
1). Cancer
Different kinds of carcinogenic (cancer-related) problems have been linked to poor air quality.
One of these is breast cancer.
Studies have shown that the exposure to air pollutants like methylene chloride, increases the risk of breast cancer among women [6].
This is corroborated by surveys which observed a higher risk (and rate of prevalence) of breast cancer for women who live close to major highways [5] and/or are exposed to poor-quality air at work.
Leukemia (blood cancer) is also associated with poor air quality and air pollution, especially among children [9]. This association mostly involves occupational exposure to benzene; an organic air-pollutant.
The most commonly-related form of cancer, with regards to poor air quality, is lung cancer. This is a bit predictable, since polluted air, when inhaled, is sure to come in contact with the lungs.
Lung cancer can be described a health condition whereby the cells which constitute the lungs, begin to alter and disintegrate, accompanied by uncontrolled cell division and the growth of tumors [18]. Among the possible causes of this condition is the inhalation of poor-quality air.
Lung cancer (also referred to as pulmonary cancer) is believed to have increased in prevalence, with the increase in the combustion of fossil fuels for energy-production and electricity generation.
The above conception is supported by evidence from studies. For example, a survey [12] revealed that the rate of lung cancer incidence between 2000 and 2016 is directly proportional to the combustion of coal in power plants.
Lung Cancer as A Health Problem Associated with Poor Air Quality (Credit: CRUK 2014 .CC BY-SA 4.0.)
Based on this understanding, it can be said, that the emissions from fossil fuel combustion, contain carcinogenic pollutants [31]. This is in fact the case. The most common carcinogenic pollutant released during the combustion of fossil fuels, is particulate matter.
This particulate matter usually occurs in the form of fine sooth (generally classified as PM 2.5- that is; 2.5 microns as the average particle size), and is dominantly composed of carbon.
It is estimated, that in 2018, about 8.7 million deaths occurred globally as a result of exposure to particulate matter released from the burning of fossil fuels [15].
Another major cause of lung cancer is cigarette smoking [39].
This is yet a case of poor air quality, since smoking of cigarettes leads to inhalation of several toxic chemical compounds, including aromatic amines, aldehydes, heterocyclic amines, N-nitrosamines, volatile hydrocarbons, miscellaneous organic compounds, nitro compounds, inorganic compounds, and metals [21].
Lung cancer may occur at various levels of severity. It typically involves abnormal patterns of cell growth in one or both lungs, and impairment of the oxygen-carrying capacity of the lungs, which ultimately affects the entire respiratory system.
2). Stroke as a Disease Caused by Poor Air Quality
Studies have repeatedly indicated that a link exists between poor air quality (a state of air pollution) and stroke [32].
Like other cardiovascular diseases, stroke can be induced by impairment of the respiratory process. When long-term exposure to poor-quality air (and air pollutants) occurs, the arteries in the brain may become hardened, thereby increasing blood pressure and heightening the risk of formation of blood clots in the brain [22].
In the event that such blood clots are formed, the supply of blood to the brain may be cut-off at some point, resulting in a stroke. The outcomes of strokes are often detrimental, including death and brain damage. Over the past decades, evidence suggests that air pollution is responsible for 14% of all deaths associated with stroke [32].
3). Coronary Heart Disease
Coronary heart disease, has been found to be significantly related to poor air quality.
Also known as ‘Ischemic heart disease’, this condition is caused by exposure to high concentrations of air pollutants like nitrogen oxide and particulate matter, which cause premature aging of blood vessels, thereby contributing to the rapid buildup of calcium in the coronary arteries [25].
Another term used to describe this buildup of calcium in the coronary arteries, is atherosclerosis or atherosclerotic calcification [24]. The ultimate outcome of this is the formation of blockages which prevent the flow of blood to the heart and other parts of the body.
4). Chronic Obstructive Pulmonary Disease (COPD)
There are in fact various health problems which fall under the term; “Chronic Obstructive Pulmonary Disease”.
As the term implies, these illnesses involve obstruction of the respiratory pathway, and breathing difficulties [16]. Diseases in this category include chronic bronchitis and emphysema. These diseases all involve lung damage, by air pollutants.
As of 2021, at least 16 million Americans suffered from COPD [4]. When individuals suffering from COPD also suffer from pneumonia, the risk of respiratory failure increase drastically.
5). Pneumonia as a Disease Caused by Poor Air Quality
Pneumonia is a prominent, acute lower respiratory infection (ALRI), which has been linked to poor air quality conditions.
Specifically, it has been observed that the risk of occurrence and exacerbation of pneumonia is increased by exposure to fine particulate matter [19]. Death as a result of pneumonia is also much more likely when the affected individual is exposed to air pollutants.
Generally, the incidence of pneumonia occurrence is higher among children and the elderly [37; 40]. Symptoms include vomiting, nausea, loss of appetite, mucous cough, and shortness of breath.
6). Asthma
Approximately 25 million Americans suffered from asthma as at 2019 [3].
Poor air quality is an instrumental factor with regards to asthma, as it both increases the risk of asthma attacks, and worsens the symptoms of the disease [28].
Common symptoms of asthma include throat irritation, chest pain. rapid heart rate, cough, and shortness of breath [17].
Global Effect of Poor Air Quality
Annually, about 4.2 million deaths occur as a result of air pollution around the world [35].
The illnesses which lead to these deaths prominently include lung cancer, stroke, and heart disease.
A major cause for concern with respect to this issue is the fact that over 90% of the global population inhabits areas where the air quality is above WHO recommended limits. However, the health effects of air pollution are most prevalent in low and middle-income regions [34].
Major Pollutants that Affect Air Quality and Health
1). Carbon Monoxide (CO)
Occurring as an odorless and colorless gas, carbon monoxide is most-often produced from the incomplete combustion of fossil fuels [2].
The gas may be released from power plants, automobile engines, industrial manufacturing machinery, and propane heaters.
Carbon monoxide is known to be very toxic, so that when it is introduced into the bloodstream, it inhibits the oxygen-carrying capacity of the blood [10]. This can be fatal, resulting in rapid death in extreme cases.
Other effects of carbon monoxide ingestion include nausea, dizziness, fatigue, blurred vision, shortness of breath, and dementia.
2). Particulate Matter
This pollutant is perhaps the most important, with regards to air quality and health.
Particulate matter refers to both solid and liquid particles suspended in the air. These particles may vary in size across a fairly-broad range, however, they are generally small enough to penetrate the lungs and bloodstream [36].
The sources of particulate matter, vary widely, and include automobile engines, heaters, power plants, industrial manufacturing outlets, and construction sites. Fossil fuel combustion, however, is known to be the primary source of particulate matter.
Health problems resulting from (or exacerbated by) exposure to particulate matter, include emphysema, asthma, COPD and bronchitis [11].
Also, the potential harmfulness of particulate matter generally increases as the particles themselves decrease in size, as smaller particles are more likely to be introduced into the delicate organs of the body.
3). Lead as a Pollutant that Affects Air Quality
Typically, lead as an air pollutant, occurs in the form of tiny, suspended particles. This implies that it is convenient to classify this pollutant as particulate matter.
However, the uniqueness of lead as a metal makes it better to discuss it as a separate category of pollutant from particulate matter. The major sources of lead in the atmosphere include industrial outlets and automobile engines.
After it has been introduced into the atmosphere as an air pollutant, lead degrades air quality. It can be ingested as a result of exposure of polluted air, coated surfaces, and polluted soils.
Efforts to reduce the concentration of lead in the atmosphere have been fairly successful over the years. The intensity of these efforts can be attributed to the high toxicity of lead itself, and the urgency of need, to limit exposure of the ecosystem to this pollutant.
In the United States, a decrease of about 86 percent in atmospheric lead concentrations was achieved between the years 2010 and 2020 [8].
4). Ground-Level Ozone
Natural ozone occurs in the troposphere, and acts as a protective covering for the Earth, from ultraviolet radiation which the Sun releases.
However, ground-level ozone is not a naturally-occurring gas, but typically results from the reaction of anthropogenic (human activity-produced) gases including Volatile Organic Compounds (VOCs) and nitrogen oxides (NOx) with sunlight [14].
It is therefore referred to as a secondary pollutant [13], since it is not directly produced from human activity, but rather results from chemical reactions of anthropogenic gases.
Physically, ground-level ozone usually occurs as a colorless and irritating gas. When inhaled, its effects on the body include congestion, coughing, chest pain and throat irritation.
Ozone is also one of the major components of smog.
5). Volatile Organic Compounds (VOCs)
Volatile Organic Compounds are a group of chemical substances containing carbon, which include aldehydes, organic acids, and alcohols.
The sources of VOCs may be indoor or outdoor. Outdoor sources include fossil fuel and biomass combustion, and industrial manufacturing processes; whereas indoor sources include man-made products like solvents, synthetic polymers, and refined wood.
One of the points of relevance, of VOCs, is their role in the chemical reactions that form ground-level ozone.
Exposure to VOCs has been linked to several health problems and effects like respiratory illness, dermal ailments, fatigue, and headache. Studies have also suggested that VOCs are carcinogenic [20; 38].
6). Sulfur Dioxide (SO2) as a Pollutant that Affects Air Quality
With its composition being dominantly composed of sulfur and oxygen, sulfur dioxide is a product of the combustion of materials which contain the element; sulfur. Examples of such sulfur-containing materials include fossil fuels like petroleum and coal.
Sulfur dioxide (SO2) has a number of defining, physical characteristics. It occurs as a toxic, colorless and pungent gas.
Acid rain, which is one of the known, hazardous effects of industrialization, forms when sulfur dioxide gets dissolved in water during precipitation. It is known to cause significant damage to infrastructure, and the entire ecosystem.
As a pollutant, sulfur dioxide is irritating, leading to respiratory problems that affect the throat, lungs and eyes in living organisms [23].
Sulfur dioxide may also contribute to the formation of secondary particulate matter (also called sulfate aerosols) by reacting with other compounds like nitrogen dioxide, carbon monoxide, lead and ozone.
7). Nitrogen Monoxide (NO)
As an air pollutant, perhaps the most significant attribute of nitrogen monoxide is the role played by this gas in the formation of ground-level ozone, which is the product of chemical reaction between nitrogen monoxide and volatile organic compounds (VOCs).
Like sulfur dioxide, nitrogen monoxide in the atmosphere, forms acid rain by dissolution in water.
8). Nitrogen Dioxide as a Pollutant that Affects Air Quality
Nitrogen dioxide (NO2) is commonly formed by the oxidation of nitrogen monoxide (NO). The following chemical equation represents this oxidation reaction;
2NO + O2 – 2NO2(g)
Combustion of fossil fuels and plant biomass can result in atmospheric emission of nitrous oxide, and decline in air quality. This pollutant also contributes to the formation of ground-level ozone, acid rain, and secondary particulate matter.
9). Ammonia (NH3)
Physically, ammonia occurs as a colorless, pungent gas [33]. Chemically, the gas is known to be alkaline, soluble, and highly reactive.
Sources of ammonia are both anthropogenic and natural. One of the most prominent, anthropogenic sources of ammonia is agriculture [30]. Ammonia is a major component of livestock waste, and soil fertilizer.
Prolonged exposure to ammonia results in throat, nasal and respiratory irritation [26]. It may contribute to acidification and eutrophication of aquatic and terrestrial ecosystems, as well as the formation of particulate matter.
What Groups are Most Vulnerable to the Effects of Low Air Quality?
1). Children
The risk of health problems on exposure to pollutants, is relatively high for children. There are some reasons behind this.
One of such reasons is the fact that children have narrower air passages, which are more easily obstructed when irritated and/or inflamed. These characteristics also place children at a higher risk of lower respiratory illnesses like asthma.
Studies have revealed a higher risk of asthma for children who engage extensively in outdoor activity, and live in ozone-polluted areas [29]. Also, asthmatic children are more likely to develop severe ailments like bronchitis, when exposed to toxic gases in areas with poor air quality.
Poor air quality has also been linked to impaired brain development among children [1]. Exposure to fine particulate matter (PM 2.5) may alter a child’s brain size, increasing the risk of cognitive problems.
A similar case exists for children in the womb of nursing mothers, who are exposed to polluted air. Health problems which are likely to manifest in such children include neural tube defects, autism, and high blood pressure.
2). Adults
Active adults are at a risk of contact with air pollutants, mainly because of their exposure in the course of outdoor activity.
Particularly when engaged in energetic activity, such as occupational-work and exercise, these adults breathe faster as well as more deeply, thereby bringing more air into contact with the lungs.
3). Older Adults
This group, which we may also refer to as theelderly, is vulnerable to health effects of air pollution, mainly because of weakened immunity, as well as the potential occurrence of other ailments like diabetes, cardiovascular disease, or lung disease, in such individuals.
Exposure to particulate matter in areas with low air quality, has been associated with neurological problems in older adults. Such problems include Alzheimer’s disease, Acute Dementia and Parkinson’s disease [27].
4). Middle-Low Income Earners
Members of this category may otherwise be referred to as rural dwellers, since majority of them reside in rural areas.
For such individuals, the risks of health problems due to air pollution, are both occupational and domestic.
Occupational exposure is a significant risk-factor, because of the relatively-crude approaches used to carry out labor in rural areas. An example of this can be found in rural coal mines, where workers are often exposed to hazardous pollutants like nitrogen oxides, particulate matter, carbon dioxide and sulfur dioxide.
The workers in these coal mines stand a high risk of suffering from health ailments like asthma, bronchitis and cancer.
Rural Coal Mines, Poor Air Quality, and Exposure to Pollutants (Credit: International Accountability Project 2013 .CC BY 2.0.)
Aside the degradation of air quality, and its associated health problems, poor air quality in rural coal mines is associated with other hazards like fire explosions, greenhouse emissions, and global warming.
Agricultural activity also serves as an avenue of occupational exposure for rural dwellers. These activities, which include fertilizer application and livestock feeding, involve the emission of air pollutants like ammonia.
Domestic exposure often occurs in the form of contact with gaseous emissions from the burning of plant biomass, such as firewood.
Pollutants released during the burning of plant biomass include carbon dioxide, nitrogen oxides, particulate matter and carbon monoxide.
The exposure of middle-to-low-income earners, to health risks as a result of air pollution, is also aggravated by the fact that these individuals are not usually able to access helpful infrastructure like air-purifying systems and health care facilities.
Below is a summarized list of groups most susceptible to health problems as a result of poor air quality;
-Children (including infants and individuals up to 17 years of age)
-Active Adults (including individuals aged 18 and above)
-Older Adults (including individuals aged 65 and above)
-Individuals who live or work close to busy highways
-Individuals with significant outdoor exposure, as a result of work, living conditions, or other forms of activity (such as physical exercise)
-Middle-to-low-income earners and rural dwellers
-Smokers and other individuals exposed to cigarette-related emissions
-Individuals with underlying health problems like bronchitis, asthma, COPD and emphysema
Strategies to Minimize the Health Effects of Air Pollution and Poor Air Quality
1. Use of face masks to protect the nose and mouth. This is especially useful in areas where poor air quality is caused by particulate matter
2. Installation of air purifiers. Residential buildings, offices and the interior of automobiles, can benefit from this option
3. Tree-planting. This is especially effective because trees can serve as natural sinks that absorb air pollutants, and produce more oxygen, thereby reducing the concentration of these pollutants in the atmosphere
4. Minimizing the use of products with harmful gaseous emissions, such as some types of paints
Because air quality directly determines the degree of purity, or pollution of air, it is capable of affecting the health of living organisms.
Good air quality has no notable effect whatsoever, on health. On the other hand, poor air quality has been linked to a significant number of health problems.
Cancer is an example of a health problem associated with poor air quality. Different forms of this illness can develop (or worsen) as a result of exposure to air pollutants. Lung cancer, Leukemia and breast cancer are inclusive of these forms.
Stroke is yet another ailment related to poor air quality. It occurs when the arteries become impaired, often leading to a restriction of blood-flow to the brain.
Coronary (or Ischemic) heart disease is similar in its cause of occurrence, to stroke. It is usually a result of the impairment of coronary arteries, often after prolonged exposure to air pollutants.
Breathing difficulty is common for individuals suffering from chronic obstructive pulmonary disease (COPD). This is also often a result of exposure to air pollutants like particulate matter. Asthma and pneumonia are other examples of health problems associated with poor air quality.
Globally, over 4 million deaths are believed to occur every year in relation to air pollution. This is strongly influenced by the rates of industrialization, electricity generation and fossil fuel burning. It can also be attributed to the fact that a large fraction of the human population is exposed to polluted air, in urban and industrial areas.
Pollutants which are responsible for degrading air quality, include various chemical substances, some of which are greenhouse gases. Nitrogen Monoxide, sulfur dioxide, carbon monoxide, lead, ground-level ozone, ammonia, nitrogen dioxide and carbon monoxide, are all examples.
Children are among the most vulnerable members of the human population, with respect to the health effects of air pollution and poor air quality in general. Reasons for this include the fact that children have more-delicate respiratory organs than adults.
Exposure of nursing mothers to air pollutants can also result in impaired development of children.
Active adults are often exposed to polluted air, as a result of their occupation, and other daily activities. While this group is the least likely to be affected, prolonged exposure can still have negative health effects.
Older adults are susceptible to air pollution-related health problems mostly due to weakened immune systems and, in some cases; underlying health challenges.
For middle-low-income earners; the problem of poor air quality is often severe, due to the exposure of these individuals to pollutants at home and at work. Rural coal mining is an example of the unfavorable health conditions that expose these individuals to pollutants.
Some measures which can be taken, to reduce the risk of health problems in relation to air quality, include the use of face masks, installation of air purifiers, tree-planting, and the adoption of renewable energy alternatives.
