Effects of Air Pollution & Greenhouse Gases

Air pollution is when harmful substances mix with the air we breathe. Clean, dry air is mostly nitrogen (about 78%) and oxygen (about 21%), with tiny amounts of noble gases and carbon dioxide. Some pollutants warm the planet (greenhouse gases), while others harm health and the environment directly.

Key air pollutants and their effects

• Carbon dioxide ($\mathrm{CO_2}$): Produced by complete combustion of fuels. Higher levels strengthen the greenhouse effect, causing global warming and climate change.
• Methane ($\mathrm{CH_4}$): Released from rotting vegetation, landfill, rice fields, and animal digestion. A strong greenhouse gas; rising levels increase global warming.
• Carbon monoxide ($\mathrm{CO}$): Formed by incomplete combustion. A toxic gas that reduces the blood’s ability to carry oxygen, leading to headaches, dizziness, and can be fatal.
• Particulates (soot/dust): Tiny solid particles from incomplete combustion and vehicles. Irritate lungs, increase risk of respiratory problems and some cancers, and reduce visibility.
• Oxides of nitrogen ($\mathrm{NO_x}$): Made in hot car engines when nitrogen and oxygen react. Cause acid rain, photochemical smog, and breathing difficulties.
• Sulfur dioxide ($\mathrm{SO_2}$): From burning sulfur-containing fossil fuels. Causes acid rain, which damages lakes, soils, forests, and corrodes buildings.

How greenhouse gases warm Earth

Think of Earth wearing a thin blanket. The Sun’s energy warms the surface. Greenhouse gases absorb, re-emit and reflect thermal (heat) energy, reducing the amount that escapes to space. With more $\mathrm{CO_2}$ and $\mathrm{CH_4}$, the “blanket” gets thicker, leading to global warming, which drives climate change (e.g. melting ice, sea level rise, heatwaves, and changing rainfall patterns).

Helpful chemical equations

Complete vs incomplete combustion and pollutant formation:

[ \mathrm{C} + \mathrm{O_2} \rightarrow \mathrm{CO_2} ]

[ 2\,\mathrm{C} + \mathrm{O_2} \rightarrow 2\,\mathrm{CO} ]

[ \mathrm{S} + \mathrm{O_2} \rightarrow \mathrm{SO_2} ]

[ \mathrm{N_2} + \mathrm{O_2} \xrightarrow{\text{high }T} 2\,\mathrm{NO} ]

Common misconceptions

• The greenhouse effect is not “bad” by itself; a natural level keeps Earth warm enough for life. The problem is the enhanced greenhouse effect.
• Ozone layer damage is different from the greenhouse effect. Ozone protects from UV; greenhouse gases trap heat.
• $\mathrm{CO}$ (toxic) is different from $\mathrm{CO_2}$ (non-toxic but a greenhouse gas).

Reducing harm (overview)

• Decrease fossil fuel use; switch to renewables and hydrogen where suitable.
• Plant trees to remove $\mathrm{CO_2}$ by photosynthesis.
• Use catalytic converters in cars to reduce $\mathrm{NO_x}$ and $\mathrm{CO}$.
• Use low-sulfur fuels to cut $\mathrm{SO_2}$ and reduce acid rain.