PrintThe pollutants that are emitted directly from a combustion process – or the products of combustion - are called “primary pollutants.” We just described these products earlier in the lesson, now we will look at their impact on the environment and human health.
Carbon Dioxide (CO2)
Carbon dioxide (CO2) is not a pollutant in the sense that would directly harm our health, but it is a proven greenhouse gas. It has an ability to absorb infrared radiation that is escaping from the surface of the earth, causing the atmosphere to warm up. Excessive emission of CO2 along with other greenhouse gases are linked to climate change, which is reaching a critical point.
Carbon Monoxide (CO)
As we learned earlier, Carbon monoxide, or CO, is a colorless, odorless and tasteless gas that is formed when carbon in fuel is not burned completely.
At much higher levels of exposure not commonly found in ambient air, CO can be poisonous, and even healthy individuals can be affected. Exposure to elevated levels of CO may result in:
- visual impairment;
- reduced work capacity;
- reduced manual dexterity;
- poor learning ability;
- difficulty in performing complex tasks.
The health threat from levels of CO sometimes found in the ambient air is most serious for those who suffer from cardiovascular disease such as angina pectoris.
In the human body, Hemoglobin (an iron compound) in the blood carries the oxygen (O20) from the lungs to various tissues and transports back carbon dioxide (CO2) to the lungs. Hemoglobin has 240 times more affinity toward CO than it does for oxygen. Therefore, when the hemoglobin reacts with CO, it reduces the hemoglobin that is available for the transport of O2. This in turn reduces oxygen supply to the body's organs and tissues.
Sulfur Dioxide (SO2)
High concentrations of SO2 can result in the following health problems:
Short-term exposure
- Adults and children with asthma who are active outdoors will experience temporary breathing impairment.
- Individuals with asthma may experience breathing difficulties with moderate activity and may exhibit symptoms such as wheezing, chest tightness, or shortness of breath.
Long-term exposure (along with high levels of PM)
- Aggravation of existing cardiovascular disease
- Respiratory illness
- Alterations in the lungs’ defenses
The subgroups of the population that may be affected under these conditions include individuals with heart or lung disease, as well as the elderly and children.
The body's reaction to regular and acidic air
Instructions: Click on the types of air and observe what happens for each. (Note: The animation has no audio.)
As a person breathes, regular air enters the lungs through open passageways, filters through the lungs and exits the body through the same open passage as carbon dioxide. However, when the air is acidic, it causes the airways to restrict, and the body must now use twice the energy to evacuate the same amount of carbon dioxide.
Together, SO2 and NOx (discussed on the next page) are the major precursors to acidic deposition (acid rain), which is associated with the acidification of soils, lakes, and streams and accelerated corrosion of buildings and monuments. We will talk more about this in the next section. SO2 also is a major precursor to PM 2.5, which is a significant health concern, and a main contributor to poor visibility.