When Defenses Fail: Particles in the Lungs
Learning Objectives
Students will be able to:
- Explain how PM2.5 bypasses respiratory defenses
- Describe the inflammatory response to particles
- Connect particle exposure to respiratory conditions
- Identify who is most vulnerable to particle exposure
The PM2.5 Problem
PM2.5 particles are the perfect size to cause harm:
- Small enough to bypass nose hairs and reach deep into lungs
- Small enough to settle in the alveoli
- Too small for macrophages to easily engulf
- Large enough to carry toxic chemicals on their surface
What Happens When Particles Reach the Alveoli?
Step 1: Particles Deposit
PM2.5 particles land on the thin, moist surface of alveoli.
Step 2: Body Detects Invaders
Cells recognize foreign particles and send chemical signals.
Step 3: Inflammation Begins
Inflammation = The body's attempt to fight off the threat
- Blood vessels dilate (get wider)
- More immune cells rush to the area
- Fluid accumulates
- The area becomes red, warm, and swollen
Step 4: Chronic Damage (with repeated exposure)
If particles keep coming, inflammation becomes chronic. This leads to scarring, reduced lung function, and disease.
Short-Term vs. Long-Term Effects
Short-Term (hours to days)
- Coughing
- Throat irritation
- Runny nose
- Shortness of breath
- Chest tightness
- Asthma attacks (if asthmatic)
- Fatigue
Long-Term (months to years)
- Reduced lung function
- Development of asthma
- Worsening of COPD
- Increased respiratory infections
- Cardiovascular effects
- Possible cancer risk
- Shortened lifespan
Ultrafine Particles: The Smallest Threat
Particles smaller than 0.1 μm (100 nanometers) are called ultrafine particles:
| Property | Why It's Concerning |
|---|---|
| Can cross alveolar membrane | Enter bloodstream directly |
| Very high surface area | Carry lots of toxic chemicals |
| Too small for macrophages | Body can't easily remove them |
| Can reach other organs | Effects throughout body (heart, brain) |
Who Is Most Vulnerable?
Children
- Breathe faster (more exposure per body weight)
- Lungs still developing
- Spend more time being active
- Closer to ground (dust)
Elderly
- Weaker immune response
- May have existing conditions
- Less lung reserve capacity
- Slower recovery
People with Asthma
- Airways already inflamed
- Particles trigger attacks
- Smaller airways more sensitive
- Can be life-threatening
People with Heart/Lung Disease
- Less reserve capacity
- Additional stress on system
- Higher risk of serious events
- May not tolerate even moderate exposure
The Asthma Connection
Asthma = A chronic condition where airways are inflamed and hypersensitive
- Relaxed muscles
- Open passages
- Normal mucus
- Air flows easily
- Muscles tighten
- Passages narrow
- Excess mucus
- Difficulty breathing
PM2.5 is a known asthma trigger. On high pollution days, asthma ER visits increase significantly.
Protecting Vulnerable People
- Monitor air quality — Check AQI before outdoor activities
- Improve indoor air — Filtration and ventilation
- Reduce indoor sources — Avoid candles, incense, smoking
- Create clean air spaces — Portable air cleaners in bedrooms
- Know warning signs — Increased symptoms, reduced function
Key Takeaway
When particles reach the alveoli, they trigger inflammation—the body's attempt to fight off the invaders. Short-term exposure causes irritation and symptoms; long-term exposure can cause permanent damage. PM2.5 and ultrafine particles are especially harmful because they bypass our defenses and can even enter the bloodstream. Children, elderly, and people with existing conditions are most at risk.