Cassá de la Selva PM2.5 (pm25) Levels

🔬What is PM2.5?

PM2.5 refers to fine particulate matter smaller than 2.5 micrometres in diameter — about 30 times thinner than a human hair. These particles penetrate deep into the lungs and can enter the bloodstream, making PM2.5 the most dangerous common air pollutant.

🏭How is PM2.5 Produced?

PM2.5 originates from both natural and human-made sources. Primary PM2.5 is emitted directly from vehicle tailpipes (especially diesel engines), coal and biomass combustion, industrial processes like cement and steel manufacturing, construction activity, and agricultural crop residue burning. Secondary PM2.5 forms in the atmosphere through chemical reactions — sulphur dioxide (SO₂) converts to sulphate particles, nitrogen oxides (NOₓ) form nitrate particles, and volatile organic compounds (VOCs) undergo oxidation to create organic aerosols. Natural sources include wildfires, sea spray, volcanic eruptions, and wind-blown dust. In many cities, secondary formation accounts for 40–60% of total PM2.5, making it harder to control than directly emitted particles.

🫁Health Effects

PM2.5 is the single most harmful common air pollutant. At just 2.5 micrometres or smaller, these particles bypass the body's natural defences — nose hairs and mucus cannot filter them. They penetrate deep into the alveoli (air sacs) of the lungs and cross into the bloodstream.

Short-term exposure (hours to days): irritation of eyes, nose, and throat; aggravated asthma; increased heart rate; reduced lung function; and higher risk of heart attacks and strokes in vulnerable individuals.

Long-term exposure (months to years): chronic bronchitis, reduced lung development in children, lung cancer (classified as Group 1 carcinogen by IARC), cardiovascular disease, and reduced life expectancy. The Global Burden of Disease study attributes over 4 million premature deaths annually to ambient PM2.5 exposure worldwide.

Most vulnerable groups: children under 5, adults over 65, pregnant women, and people with pre-existing heart or lung conditions.

🌍Environmental Impact

PM2.5 reduces visibility by scattering and absorbing light, creating the haze commonly seen over polluted cities. It damages crops and forests by settling on leaves and blocking photosynthesis. Black carbon — a component of PM2.5 — absorbs sunlight and contributes to climate warming. When deposited on snow and ice, it accelerates melting. PM2.5 also acidifies lakes and rivers when washed out of the atmosphere by rain, harming aquatic ecosystems.

🛡️How to Protect Yourself

Check AQI before outdoor activities and reduce exertion when PM2.5 levels are elevated. Wear a well-fitted N95 or KN95 mask during high-pollution episodes — surgical and cloth masks do not filter PM2.5 effectively. Keep windows closed when outdoor air quality is poor and use an air purifier with a HEPA filter indoors. Avoid exercising near heavy traffic. If you cook with solid fuels (wood, dung, coal), ensure proper ventilation or switch to cleaner fuels.

📏Safe Levels & Guidelines

WHO (2021): 5 µg/m³ annual mean, 15 µg/m³ 24-hour mean — the strictest global guideline.

US EPA NAAQS: 9 µg/m³ annual mean, 35 µg/m³ 24-hour (revised 2024).

EU Directive: 25 µg/m³ annual mean (proposed revision to 10 µg/m³ by 2030).

India NAAQS (CPCB): 40 µg/m³ annual mean, 60 µg/m³ 24-hour mean.

Every 10 µg/m³ increase in long-term PM2.5 exposure is associated with a 6–13% increase in all-cause mortality.

📡How is PM2.5 Measured?

PM2.5 is measured using gravimetric samplers (reference method) that draw air through a filter for 24 hours, then weigh the collected particles. Real-time monitoring uses Beta Attenuation Monitors (BAM), which measure the reduction in beta radiation passing through a filter tape, or Tapered Element Oscillating Microbalance (TEOM), which detects mass changes on a vibrating element. Low-cost sensors (e.g., PurpleAir, PMS5003) use laser light scattering — they are less accurate but enable dense monitoring networks.

💡Key Facts

A single cigarette produces approximately 12 mg of PM2.5 — breathing Delhi's air on a bad day (AQI 400+) is equivalent to smoking 15–20 cigarettes.

PM2.5 is about 30 times thinner than a human hair and 100 times smaller than a grain of sand.

Indoor air can be 2–5 times more polluted than outdoor air — cooking, candles, and incense are major indoor PM2.5 sources.

The economic cost of PM2.5 air pollution is estimated at $8.1 trillion globally (World Bank, 2022), equivalent to 6.1% of global GDP.