Have you ever admired red skies or criticised early morning haze? Atmospheric aerosols, tiny solid or liquid particles suspended in air, also called Particulate Matter (PM), are responsible for the myriad hues created by the evening sky. Not just that, aerosols impact the global climate and play a role in ozone depletion. These particles generally range from about a nanometre to ten micrometre in size and are either directly emitted or formed by the conversion of a gas to particles.

Atmospheric aerosols are found in many shapes and sizes. The most vernacular and essential terms for a layman are PM10 and PM2.5 size fractions. PM2.5 is more harmful given its minute size and thus, has higher ability to reach our inner respiratory system. PM2.5 is released majorly by combustion of solid and liquid fuels. They have an affect on our climate and atmosphere. 

Depending on the composition, aerosols scatter or absorb Sun’s radiation, and thus affect Earth’s energy budget. Aerosols of industrial pollutants that contain sulphates and nitrates cause a cooling effect in the atmosphere as they reflect the incoming radiation, countering the warming effect of greenhouse gases. Sounds positive? Just hold on. The combustion in industries also consists of PM2.5 aerosols, which has large portions of toxic metals and volatile organic carbons, which are extremely harmful to human health. These aerosols can cause an array of respiratory, cardiovascular and/or pulmonary health risks; even leading to lung cancer in worst scenarios.

The next time you admire the reddening sky, remember that there is so much of physics and chemistry at play to treat your sight!