Introduction to the Principle of Ultraviolet Light

Introduction to Ultraviolet Radiation

Ultraviolet radiation (abbreviated as UV) is electromagnetic radiation with a wavelength between 100nm and 400nm, shorter than visible light but longer than X-rays. Sunlight contains some ultraviolet radiation (UVA, UVB). Arc lamps, mercury lamps, and black lights also emit ultraviolet radiation. Although ultraviolet radiation is not classified as ionizing radiation, it can induce chemical reactions that cause certain substances to fluoresce.

Classification of Ultraviolet Radiation
 

Name

Abbreviation

Wavelength (unit: nm)

Longwave Ultraviolet

UVA

315nm~400nm

Midwave Ultraviolet

UVB

280nm~315nm

Shortwave Ultraviolet

UVC

100nm~280nm


Classification in Daily Life

UVA: Longer wavelength, ranging from 320 to 400nm, can penetrate clouds and glass into indoors or vehicles, and can penetrate the skin to the dermis, causing tanning. UVA can be subdivided into UVA-2 (320~340nm) and UVA-1 (340~400nm). UVA-1 has the strongest penetrating power, reaching the dermis and causing tanning, which is the most harmful to the skin but also the easiest to overlook, especially outside of summer. Although the intensity of UVA-1 is weaker, it still exists and can accumulate over time, causing skin damage, particularly sagging skin, loss of elasticity, and melanin deposition, among others. UVA-2, like UVB, can reach the skin's epidermis, causing sunburn, redness, pain, xerosis, and loss of transparency.

UVB: Medium wavelength, ranging from 280 to 320nm, absorbed by the ozone layer, can cause sunburn, redness, swelling, pain, and heat, with severe cases possibly leading to blisters or peeling.

UVC: Wavelength ranging from 100 to 280nm, but since wavelengths below 200nm are vacuum ultraviolet, they can be absorbed by air. Therefore, the wavelength of UVC that penetrates the atmosphere is between 200 and 280nm. The shorter the wavelength, the more dangerous it is. However, due to the filtering effect of the ozone layer, only a small amount reaches the Earth's surface.

Ultraviolet Radiation

Harmful Effects

Excessive exposure to ultraviolet radiation can lead to sunburn and certain forms of skin damage. However, the most lethal form, malignant melanoma, is mostly caused by indirect DNA damage (free radicals and oxidative stress), found in 92% of melanomas possessing mutations attributed to UV characteristics. For humans, long-term exposure to ultraviolet radiation may result in acute or chronic health effects on the skin, eyes, immunological system, etc. Additionally, UVC can cause varying degrees of mutations or carcinogenic adverse effects. UVC is the highest energy and most dangerous form of ultraviolet radiation. However, it is seldom a concern as it gets filtered during its passage through the atmosphere. Care should be taken regarding exposure risks when they are used in sterilization equipment.

UVC Sterilization

UVC sterilization offers advantages such as speed, thoroughness, no contamination, easy operation, and low usage and maintenance costs. UVC sterilization is faster than chlorinated chemical and ozone sterilization. High-intensity, high-energy UVC can completely eliminate germs within seconds, whereas chlorinated chemical and ozone sterilization requires several minutes. UVC sterilization is effective against almost all bacteria, viruses, parasites, pathogens, and algae, etc., and does not cause secondary contamination, leaving no toxic substances behind.

Chlorinated chemical and ozone sterilization cannot effectively eliminate certain more harmful parasites (such as Cryptosporidium, Giardia, etc.). Additionally, chlorinated chemical and ozone sterilization can lead to bacteria developing drug resistance, and prolonged exposure can directly or indirectly produce toxic substances that are carcinogenic to humans, affecting human health.

Comparison Table of Sterilization Using Ultraviolet UVC, Chlorine, and Ozone

Item

Ultraviolet UVC

Chlorine

Ozone

Disinfection Method

Physical

Chemical

Chemical

Cost Investment

Low

Low

High

Operating Cost

Low

Medium

High

Maintenance Cost

Low

Medium

High

Disinfection Effectiveness

Excellent

Good

Unstable

Disinfection Time

1~5 seconds

25~45 minutes

5~10 minutes

Harmfulness to Humans

Very Low

Medium

High

Residual Toxic Substances

None

Yes

Yes

Impact on Water and Air

None

Yes

Yes