What is an aerosol?
Is it harmful to humans?

An aerosol is a suspension of fine solid particles in atmospheric air.
Aerosols are often not or barely visible to the human eye and recently we often hear them called as PM10 (particle size less than 10μm), PM2.5 (particle size less than 2.5μm), etc. according to the size of particles.

Particles originated in coal, oil, natural gas, etc. may bring harmful effect to humans because those particle size are very small and possible to come deep into the lungs.

Aerosols can be generated from both natural processes, such as sea spray and dust storms, and human activities including pollution from vehicles and industrial emissions.

Aerosol particles generally have diameters less than 1 micrometer (μm), allowing them to remain suspended in the atmosphere for extended periods. They can vary in size, with classifications such as PM2.5 (particles smaller than 2.5 μm) and PM10 (particles between 2.5 and 10 μm) being common in environmental science.

Aerosols can be classified into primary aerosols, which are emitted directly into the atmosphere (e.g., dust, smoke), and secondary aerosols, which form from chemical reactions in the atmosphere (e.g., sulfate aerosols from sulfur dioxide emissions).

Aerosols play a significant role in climate dynamics by influencing cloud formation and solar radiation absorption and may also impact to health issues because fine particulate matter can penetrate deep into the lungs and enter the bloodstream which may lead to various respiratory and cardiovascular problems.

Aerosols have a complex and significant impact on climate change.
Typical impacts are cooling effect and warming effect on Earth's climate.

Most aerosols have an overall cooling effect on the Earth's climate:

- They reflect incoming sunlight back to space before it reaches the Earth's surface and it results reducing the amount of solar energy absorbed.

- Light-colored aerosols like sulfates from volcanic eruptions or air pollution can block sunlight and cool the atmosphere.

- Some aerosols interact with clouds, making water droplets smaller and clouds more reflective, further enhancing cooling

On the other hand, some aerosols can contribute to warming:

- Dark-colored aerosols like black carbon (soot) absorb sunlight and warm the atmosphere.

- While absorbing aerosols reduce sunlight at ground level, they heat up the atmosphere and can eventually warm the surface.

Aerosols, which are tiny particles suspended in the air, can significantly impact human health through various mechanisms. The health effects by aerosols largely depend on their size, composition and concentration in the environment.

Inhalation of aerosols can lead to respiratory problems as these particles can penetrate deep into the lungs and, depending on their size, even enter the bloodstream. This can result in acute and chronic respiratory illnesses, including asthma, bronchitis, and chronic obstructive pulmonary disease (COPD).

Aerosols are also linked to cardiovascular issues. Prolonged exposure to particulate matter in aerosols can increase the risk of heart attacks, strokes, and other cardiovascular diseases. Studies have shown that exposure to aerosols can aggravate pre-existing cardiovascular conditions and increase mortality rates due to cardiorespiratory causes.

Bioaerosols, which include microbial particles, can cause infections and allergic reactions. These particles can carry pathogens and allergens that lead to diseases such as hypersensitivity pneumonitis and other allergic conditions.

Some aerosols contain toxic substances that can lead to toxicological responses in the body. These can include irritation of the eyes, skin, and respiratory tract, as well as systemic effects if the toxins enter the bloodstream.

The health effects of aerosols are influenced by several factors, including:

Smaller particles can penetrate deeper into the lungs and have more severe health effects compared to larger particles that are typically trapped in the upper respiratory tract.

Both short-term and long-term exposures to aerosols can have health impacts, but chronic exposure is associated with more severe outcomes such as increased mortality from cardiorespiratory diseases.

The impact of aerosols can vary based on environmental conditions (e.g., urban vs. rural settings) and individual factors such as age, health status, and pre-existing conditions.

As described above, aerosols have significant impact on human health (as well as quality on industrial production process). So it is required to monitor environmental situation (concentration of aerosols) in the ambient air with continuous monitoring equipment according to the place and situation.