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Understanding Air Quality

A comprehensive guide to air quality measurements, pollutants, and their impact on health

Air quality is a critical environmental and health concern that affects millions of people worldwide. This guide explains the key concepts, measurements, and implications of air quality monitoring.

The information provided is based on scientific research and official environmental protection guidelines.

Common Air Pollutants

Learn about the major pollutants that affect air quality and their sources.

Particulate Matter (PM2.5 & PM10)

Microscopic particles that can penetrate deep into the lungs and bloodstream.

Common sources: Vehicle emissions, construction, industrial activities, smoke

Ground-level Ozone (O₃)

A reactive gas formed when pollutants react with sunlight.

Common sources: Vehicle exhaust, industrial emissions, chemical solvents

Carbon Monoxide (CO)

An odorless, colorless gas that can be harmful when inhaled in large amounts.

Common sources: Vehicle exhaust, indoor heating, industrial processes

Nitrogen Dioxide (NOâ‚‚)

A reddish-brown gas with a pungent odor that can irritate airways.

Common sources: Vehicle emissions, power plants, industrial processes

Sulfur Dioxide (SOâ‚‚)

A colorless gas with a sharp odor that can harm the respiratory system.

Common sources: Fossil fuel combustion, industrial activities, volcanic eruptions

Ammonia (NH₃)

A colorless gas with a strong odor that can form harmful particles.

Common sources: Agricultural activities, animal waste, fertilizers

How Air Quality Index (AQI) is Calculated

Understanding the methods used to calculate Air Quality Index values

US EPA AQI Calculation

The United States Environmental Protection Agency (EPA) uses a standardized formula to calculate AQI:

AQI = [(IHigh - ILow)/(CHigh - CLow)] × (C - CLow) + ILow

Where:

  • C = the pollutant concentration
  • CLow = the concentration breakpoint that is ≤ C
  • CHigh = the concentration breakpoint that is ≥ C
  • ILow = the index breakpoint corresponding to CLow
  • IHigh = the index breakpoint corresponding to CHigh

This calculation is performed for each pollutant, and the highest value becomes the AQI