- Air quality is affected by various economic and industrial activities which alter the composition of air and affect the environment locally, regionally and globally.
- It is estimated that anthropogenic sources have changed the composition of global air by less than 0.01%. However, this change has adversely affected the climate of the earth.
- Both natural and/or anthropogenic activities introduce air pollutants which can be solid (large or sub-molecular), liquid or gas into the atmosphere that pose problem to human health and other life forms on earth.
- These air pollutants include CO, SOx, NOx, SPM, CO2, ozone, photochemical smog, etc..
Classification of Air Pollutants
- Natural contaminants: Natural fog, pollen grain, bacteria, volcanic eruption, wind blown dust, lightning generated fires.
- Particulate (aerosols): Dust, smoke, fog, mists, fume.
- Gases and odor: SOx, NOx, CO, CO2, halogen compounds, hydrocarbons, radioactive compounds.
PARTICULATE MATTER (PM)
- PM is a complex mixture variable in size (0.01- 100 μm), composition (metals, nitrates, sulfate, polynuclear aromatic hydrocarbons (PAH), volatile organic compound (VOC), etc.) and concentration.
- Toxicity and penetration depends on the composition and size of the particles.
- Solid or liquid particles with sizes from 0.005 – 100 μm
- General term is aerosols
- Dust originates from grinding or crushing
- Fumes are solid particles formed when vapors condense
- Smoke describes particles released in combustion processes
- Smog used to describe air pollution particles
Health Effects of Particulate Matter
- Impact depends on particle size, shape and composition
- Large particles trapped in nose · Particles >10 μm removed in tracheobronchial system
- Particles <0.5 μm reach lungs but are exhaled with air
- Particles 2 – 4 μm most effectively deposited in lungs
- Inhalable PM includes both fine and coarse particles.
- Coarse particles
- aggravation of respiratory conditions, such as asthma.
- Fine particles
- increased hospital admissions and emergency room visits for heart and lung disease
- increased respiratory symptoms and disease
- decreased lung function
- premature death Other Effects of Particulate matter
- Decreased visibility
- Damage to paints and building materials
Table 1.8.1. Gaseous air pollutants, their properties and significance.
Table 1.8.2. Monitoring systems used to determine the quality of ambient air .
Table 1.8.3. Monitoring systems can be used to monitor air emissions .