Air pollution is a mixture of gases and tiny particles that can enter the body with every breath. Because the lungs have a huge surface area for exchanging oxygen and carbon dioxide, they are also vulnerable to harmful pollutants. Polluted air can irritate the airways, reduce lung function, and make breathing harder, especially for children, older adults, and people with asthma.
Understanding how pollutants move through the respiratory system helps people make safer choices on high pollution days.
When polluted air enters the nose or mouth, larger particles may get trapped by mucus and tiny hairs, but very small particles can travel deeper. PM2.5 can reach the alveoli, where oxygen normally moves into the blood. Ozone can react with airway tissues and trigger inflammation, coughing, and chest tightness.
Nitrogen oxides and sulfur oxides from vehicles, power plants, and factories can also form harmful particles and contribute to smog and acid rain.
Key Facts
- PM2.5 means particulate matter with diameter 2.5 micrometers or smaller.
- Gas exchange happens in alveoli, where O2 enters blood and CO2 leaves blood.
- AQI 0 to 50 is good, 51 to 100 is moderate, and higher values mean greater health risk.
- Ozone near the ground can inflame airways and make asthma symptoms worse.
- NOx and SOx can react in the atmosphere to form fine particles and acidic pollution.
- Long-term exposure to polluted air increases risk of asthma attacks, COPD, lung cancer, and reduced lung growth in children.
Vocabulary
- Particulate matter
- Particulate matter is a mixture of tiny solid particles and liquid droplets suspended in air.
- PM2.5
- PM2.5 is fine particulate matter small enough to travel deep into the lungs and reach the alveoli.
- Alveoli
- Alveoli are tiny air sacs in the lungs where oxygen and carbon dioxide are exchanged with the blood.
- Ozone
- Ground-level ozone is a reactive gas formed when pollutants react in sunlight and it can irritate lung tissue.
- AQI
- The Air Quality Index is a scale that reports how polluted the air is and how risky it may be to breathe.
Common Mistakes to Avoid
- Thinking all air pollution is visible, which is wrong because gases and PM2.5 can be invisible but still harmful.
- Assuming the nose filters out all pollutants, which is wrong because very small particles can pass deep into the bronchi and alveoli.
- Confusing ozone high in the atmosphere with ground-level ozone, which is wrong because stratospheric ozone protects life while ground-level ozone harms lungs.
- Ignoring AQI when planning outdoor activity, which is wrong because high AQI days can increase symptoms even when the air does not look smoky.
Practice Questions
- 1 A city reports an AQI of 42 in the morning and 126 in the afternoon. By how many AQI units did air pollution increase, and which reading has greater health risk?
- 2 A PM2.5 particle is 2.5 micrometers wide. A coarse dust particle is 10 micrometers wide. How many times wider is the coarse dust particle than the PM2.5 particle?
- 3 Explain why PM2.5 is more likely than larger dust particles to affect the alveoli and blood oxygen exchange.