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Air Pollution

Table of Contents

How air pollution damages your body
The brain at risk
Who faces the greatest danger
Practical steps for protection

How air pollution damages your body

Air pollution caused 4.2 million premature deaths worldwide in 2019 ^[1]. Fine particulate matter (PM2.5)—particles smaller than 2.5 micrometers—poses the greatest threat. These particles penetrate deep into lung tissue, cross into the bloodstream, and trigger systemic inflammation that affects nearly every organ system ^[2].

The cardiovascular system bears the brunt: 68% of air pollution deaths result from ischaemic heart disease and stroke ^[2]. PM2.5 exposure increases blood pressure, promotes atherosclerosis, and raises the risk of heart attacks and arrhythmias ^[3]. Even short-term exposure to elevated levels can trigger cardiac events in susceptible individuals. A 2024 WHO meta-analysis found that every 10 μg/m³ increase in long-term PM2.5 exposure raises all-cause mortality risk by about 9.5% ^[4].

The brain at risk

Recent research reveals that PM2.5 particles reach the brain through the olfactory nerve and bloodstream, triggering neuroinflammation and oxidative stress ^[5]. This accelerates cognitive decline and increases dementia risk. A 2025 study of 27.8 million Medicare beneficiaries found that PM2.5 exposure was associated with an 8.5% increased risk of Alzheimer's disease per interquartile range increase in concentration ^[5].

The association was strongest in individuals with a history of stroke, suggesting heightened vulnerability in those with existing cerebrovascular damage ^[5]. While prior cardiovascular disease may increase susceptibility, the study found that over 95% of the air pollution-Alzheimer's link came from direct brain effects rather than mediation through other health conditions.

Who faces the greatest danger

While everyone exposed to polluted air faces health risks, certain populations are more vulnerable. Children, older adults, and people with pre-existing heart or lung conditions experience more severe effects ^[3]. Low-income communities and minority populations often face higher exposure levels due to proximity to pollution sources.

The WHO recommends keeping annual PM2.5 concentrations below 5 μg/m³, yet 99% of the world's population lives in areas exceeding this threshold ^[1]. Even at levels below current regulatory standards in many countries, research demonstrates clear health impacts with no identified safe threshold ^[4].

Practical steps for protection

Indoor air quality matters as much as outdoor levels. Cooking, cleaning products, and furniture off-gassing can make indoor air 2-5 times more polluted than outdoor air. High-efficiency air filtration, proper ventilation, and reducing combustion sources indoors can significantly lower exposure.

Monitoring local air quality indexes helps guide outdoor activities. When air quality index values exceed 100, sensitive individuals should limit prolonged outdoor exertion. Above 150, even healthy adults benefit from reducing intense outdoor exercise ^[2].

References

Run HEPA purifiers on high during cooking

Gas stoves release nitrogen dioxide and PM2.5. Running your purifier on high for 30 minutes after cooking removes 80% of indoor pollutants faster than natural ventilation alone.

Place purifiers where you sleep and work

You spend 8+ hours sleeping. A HEPA unit in your bedroom delivering 5+ air changes per hour reduces nighttime PM2.5 exposure by up to 90%.

Check AQI before outdoor exercise

When AQI exceeds 100 (orange), move workouts indoors. Above 150 (red), even healthy adults should avoid prolonged outdoor exertion.

Add air-purifying plants strategically

While plants alone cannot replace filtration, spider plants and peace lilies can reduce VOC levels. Place 2-3 plants per 100 square feet for modest air quality improvement.

Eliminate combustion sources indoors

Candles, incense, and fireplaces release PM2.5 and carcinogenic compounds. Switch to LED candles and electric heating to eliminate this major indoor pollution source.

www.who.int

What is the safe level of PM2.5 exposure?

The WHO recommends keeping annual average PM2.5 below 5 μg/m³. The US EPA standard is 12 μg/m³ annually. For context, major cities often exceed 25 μg/m³. Studies show health impacts begin at levels as low as 10 μg/m³, with no truly safe threshold identified.

Can air purifiers really remove PM2.5?

Yes—true HEPA filters (H13 or H14 grade) capture 99.97% of particles 0.3 microns and larger, including PM2.5. Look for units with CADR ratings of 240+ for rooms up to 300 sq ft. Replace filters every 6-12 months depending on usage and pollution levels.

How does air pollution affect brain health?

PM2.5 particles trigger neuroinflammation and oxidative stress, accelerating cognitive decline. Studies link long-term exposure to increased dementia risk, memory loss, and reduced executive function. The particles reach the brain via the olfactory nerve or bloodstream, contributing to Alzheimer's pathology.

Is indoor or outdoor air more polluted?

It depends on your location and home. Indoor air is often 2-5 times more polluted due to cooking emissions, cleaning products, furniture off-gassing, and lack of ventilation. However, in cities with severe outdoor pollution, indoor levels may still exceed safe thresholds without proper filtration.