PM2.5 vs PM10: What's the Difference?
Understand the key differences between PM2.5 and PM10 particulate matter, their sources, health effects, and how to reduce exposure.
What Is Particulate Matter?
Particulate matter (PM) refers to tiny particles suspended in the air. These particles come in various sizes, and the size determines how deeply they can penetrate your respiratory system. The two most commonly monitored categories are PM10 and PM2.5.
PM10: Coarse Inhalable Particles
PM10 includes particles with a diameter of 10 micrometers or smaller — about one-seventh the width of a human hair.
Sources of PM10:
- Dust from roads and construction sites
- Agricultural stubble burning
- Industrial processes (cement, mining)
- Wind-blown dust from open areas
- Vehicle tyre and brake wear
Health effects: PM10 particles enter your nose and upper respiratory tract. They can irritate eyes, nose, and throat, trigger coughing, and worsen asthma. However, most PM10 is trapped by nasal hairs and mucus before reaching the lungs.
PM2.5: Fine Inhalable Particles
PM2.5 particles are 2.5 micrometers or smaller — about 30 times smaller than a human hair. These ultrafine particles can bypass your body’s natural defences entirely.
Sources of PM2.5:
- Vehicle exhaust (especially diesel)
- Burning of biomass (wood, crop residue, cow dung)
- Coal combustion in power plants and industries
- Secondary formation from gases (SO2, NOx) reacting in the atmosphere
- Cooking smoke, especially from solid fuels
Health effects: PM2.5 particles travel deep into the alveolar region of the lungs, enter the bloodstream, and affect the heart, brain, and other organs. Long-term exposure is linked to reduced lung function, heart attacks, stroke, and premature death.
Key Differences at a Glance
| Feature | PM10 | PM2.5 |
|---|---|---|
| Size | ≤10 µm | ≤2.5 µm |
| Penetration | Nose and throat | Deep into lungs and bloodstream |
| Primary sources | Dust, construction, agriculture | Combustion, vehicles, industry |
| Natural defence | Trapped by nasal hairs | Bypasses defences |
| Health impact duration | Short-term irritation | Long-term chronic effects |
| Visibility | Visible as dust | Invisible to naked eye |
Why Both Matter in India
In Indian cities, both PM10 and PM2.5 routinely exceed safe limits. The annual standard for PM2.5 is 40 µg/m³ (India CPCB) and 60 µg/m³ for PM10. Compare this to WHO guidelines of 5 µg/m³ for PM2.5 and 15 µg/m³ for PM10.
Delhi, for instance, records PM2.5 levels of 200–400 µg/m³ during winter — 40 to 80 times the WHO guideline.
How to Reduce Exposure
- For PM10: Keep windows closed on dusty days, use doormats, wet-mop floors instead of sweeping
- For PM2.5: Use HEPA air purifiers, wear N95 masks outdoors, seal windows and door gaps
- For both: Monitor local AQI readings, avoid outdoor exercise during high pollution, use recirculation mode in car AC
Key Takeaways
- PM10 is coarse dust trapped by nose/throat; PM2.5 is fine particles that enter the bloodstream
- PM2.5 comes mainly from combustion; PM10 from mechanical processes like dust and construction
- Both exceed safe limits across most Indian cities year-round
- PM2.5 poses greater long-term health risks due to deeper penetration
- HEPA filters capture both PM10 and PM2.5; N95 masks protect against both