Environmental Pollution Notes

Air quality is a descriptive measure of how clean or polluted the air is.
Monitoring air quality is vital because polluted air is detrimental to our health and the environment.
Air quality is measured using the Air Quality Index (AQI).
Air quality is influenced by health effects, physical properties, and biological properties.

A United States federal law designed to control air pollution at the national level.
Requires the Environmental Protection Agency (EPA) to develop and enforce regulations.
Regulations protect the general public from exposure to airborne contaminants hazardous to human health.
The Clean Air Act doesn't mandate EPA to establish primary National Ambient Air Quality Standards (NAAQS) at a zero-risk level.
Standards are set at a level that sufficiently reduces risk to protect public health with an adequate margin of safety.
Air quality standards are based on air quality criteria, with added safety factors.
Six outdoor pollutants regulated under the Clean Air Act:
- Carbon Monoxide
- Lead
- Ground-Level Ozone
- Particulate Matter
- Nitrogen Dioxide
- Sulfur Dioxide

Presence of any solid, liquid, or gaseous substance, including noise and radioactive radiation, in the atmosphere.
The concentration of these substances can be directly or indirectly injurious to humans, other living organisms, plants, or property.
It also interferes with normal environmental processes.

Pollutant Types:
- Primary: Directly emitted from a source.
- Examples: $SO2$ , $CO$ , VOCs, $CO2$ , $NO$ , $NO_2$ , most hydrocarbons, most suspended particles.
- Secondary: Formed in the atmosphere through chemical reactions of primary pollutants.
- Examples: $SO3$ , $H2SO4$ , $O3$ , $H2O2$ , $HNO3$ , most $NO3$ and $SO_4$ .

Classified by origin (location):
1. Natural Sources
2. Stationary Sources
3. Area Sources
4. Mobile Sources

Air pollutants are of two types:
1. Suspended particulate matter.
2. Gaseous pollutants (e.g., carbon dioxide ( $CO_2$ ), NOx).
Both natural and anthropogenic sources produce all types.
Natural Sources:
- Volcanic Eruptions
- Forest Fires
- Dust Storms
- Oceans
- Extra Terrestrial/ Cosmic/Asteroids
Anthropogenic Sources:
- Rapid Industrialization
- Transportation
- Fossil Fuel and Fire Burning
- Deforestation
- Population Growth
- Agricultural Activities
- Solid Waste Disposal
- Construction Activities
- Wars

Particles in the air consist of solids and/or liquid materials.
A particle needs to be < 10 microns ( $\mu m$ ) to be inhaled into the respiratory tract.
Relative Sizes of Particles:
- Human Hair: 50-180 $µm$
- Fine Beach Sand: 90 $µm$
- Grain of Salt: 60 $µm$
- White Blood Cell: 25 $µm$
- Grain of Pollen: 15 $µm$
- Dust Particle (PM10): < 10 $µm$
- Respiratory Droplets: 5-10 $µm$
- Red Blood Cell: 7-8 $µm$
- Dust Particle (PM2.5): 2.5 $µm$
- Bacterium: 1-3 $µm$
- Wildfire Smoke: 0.4-0.7 $µm$
- Coronavirus: 0.1-0.5 $µm$
- T4 Bacteriophage: 0.225 $µm$
- Zika Virus: 0.045 $µm$
Visibility limit for the naked eye is around 10-40 $µm$ .
Pollen can trigger allergic reactions and hay fever.
Respiratory droplets can carry smaller particles like dust or coronavirus.
Wildfire smoke can persist in the air for days or months.

Suspended Particulate Matter/Dust:
- Sources: Smoke from domestic, industrial, and vehicular soot.
- Effects: Depends on specific composition; reduces sunlight and visibility; increases corrosion; pneumoconiosis, asthma, cancer, and other lung diseases.
Fly Ash:
- Sources: Part of smoke released from chimneys of factories and power plants.
- Effects: Settles on vegetation and houses; adds to the suspended particulate matter (SPM) in the air; leachates contain harmful material.

Power plants, industries, and vehicles using petrol and diesel release gaseous pollutants like carbon dioxide, oxides of nitrogen, and Sulphur dioxide, along with particulate matter in the form of smoke.
These have harmful effects on plants and humans.

Carbon compounds (CO and $CO_2$ ):
- Sources: Automobile exhaust, burning of wood and coal.
- Effects: Respiratory problems, greenhouse effect.
Nitrogen compounds (NO and $N_2O$ ):
- Sources: Motor vehicle exhaust, atmospheric reaction.
- Effects: Irritation in eyes and lungs, low productivity in plants, acid rain damages materials.
Hydrocarbons (benzene, ethylene):
- Sources: Automobiles and petroleum industries.
- Effects: Respiratory problems, cancer-causing properties.
SPM (Suspended Particulate Matter):
- Sources: Thermal power plants, construction activities, metallurgical processes, and automobiles.
- Effects: Poor visibility, breathing problems, lead interferes with the development of red blood diseases and cancer, smog formation aggravates asthma.
Fibers (Cotton, wool):
- Sources: Textiles and carpet weaving industries.
- Effects: Lung disorders.

Poor ventilation due to faulty building design leads to pollution of the confined space.
Paints, carpets, and furniture may release volatile organic compounds (VOCs) or harmful gases such as Radon.
Use of disinfectants and fumigants may release hazardous gases.

Energy Source Replacement:
- Use of wood and dung cakes should be replaced by cleaner fuels such as biogas, kerosene, or electricity.
House Design Improvement:
- House designs should incorporate a well-ventilated kitchen.
Coverings & Segregation:
- Segregation of waste, pretreatment at source, and sterilization of rooms will help in checking indoor air pollution.

Filters:
- Remove particulate matter from the gas stream using fibrous materials, granular material, or rigid materials.
- Baghouse filtration systems are the most common, using cotton or synthetic fibers for low temperatures or glass cloth fabrics for higher temperatures (up to 290°C).
Electrostatic Precipitators (ESP):
- Dust is charged with ions, and ionized particulate matter is collected on an oppositely charged surface.
- Particles are removed by shaking or rapping the surface.
- ESPs are used in boilers, furnaces, and many thermal power plants, cement factories, and steel plants.
Inertial collectors:
- Works on the principle that inertia of SPM in a gas is higher than its solvent.
- Collects heavier particles more efficiently due to inertia being a function of the mass of the particulate matter.