We are going to discuss about the harmful effects of UV Rays on skin and its importance on earth. UV Rays or ultraviolet rays, coming from the sun has both positive and negative effects on human health. Three types of UV rays, UV-A, UV-B, UV-C.
Some UV rays are very essential for vitamin D synthesis to our body and some have harmful effects are on the eye (Cataract), skin (skin darkening, skin cancer, skin burn).
In our modern life, we use different devices( welding ) which are sources of UV Rays and we use the artificial UV rays source to disinfect medical instruments, N-95 masks, etc. We have to know how to protect ourselves from the harmful effects of UV Rays.
What is UV rays?
UV ray consists of shorter wave-length ( 10nm -400 nm) and higher energy photons ( 3 eV-124 eV) than violet-light.
Visible light ( wave-length approx 400nm-700nm ) passes through a human lens and absorbed by special molecules in the retina and by simulation in the central nervous system, we can recognize any event. But in the case of UV rays, this phenomenon does not happen in our eye and we can detect the presence of UV rays.
From low energy to high energy radiations are:
- Radio Wave
- Micro Wave
- Visible light
- Gamma Rays
Types of UV rays
UV-A ( wave-length 320-400 nm )
UV-B ( wave-length 290-320 nm )
UV-C ( wave-length 200-290 nm )
Wave-length shorter than 200 nm is mostly absorbed by the air. and below 290 nm wave-length radiation is absorbed by the ozone layer.
Solar UV rays of wave-length between 290 nm -320 nm reach the earth’s surface in small quantities and this is sufficient for sunburn on human skin.
Solar UV rays of wave-length above 320 nm can reach the earth’s surface, it can easily penetrate the ozone layer.
Sources of UV rays
The main source of UV rays is sunlight. The Sunlight reaches to earth, contains UV-B( only 5%) & UB-A( 95%). UV-C is absorbed by the Ozone layer.
- Tanning Bed: This is an electrical device which produces UV-A and it has a bed like facility where a person lay down and exposes to UV-A rays for tanning skin.
- Germicidal Lamp: This lamp emits UV-C for disinfecting purposes.
- Mercury Vapour Lamp: It is used to light a large area( Street, Stadium .etc) for its high-intensity property. This lamp generates UV-rays but in the lamp, a filter used to block these UV rays.
- Halogen light, Fluorescent.
Benefit of UV rays
UV-B rays are absorbed by the skin. UV-B interacts with a protein 7-DHC in the skin & produces vitamin D.
Vitamin D regulates the calcium level & keeps bone strong.
Why is UV-C the Most Dangerous?
UV-C radiation can cause of erythema of normal skin and can cause photokeratitis ( inflammation cornea )
UV-C also called germicidal radiation because it can kill a one-celled organism. For that property medical instrument, N-95 masks are used to sterilize.
Harmful effects of UV rays, UV-B and UV-A
A small quantity of UV-B rays reach the earth’s surface and this amount is sufficient for sunburn&skin aging. Epidemiologic evidence suggests strongly that solar UV-B rays cause skin cancer in men.
UV-A rays melanogenic (skin pigment & tanning), Erithemogenic(redness of the skin ).
What is UV-ray index (UVI)?
Due to Ozone depletion, the percentage of UV-C rays on the earth’s surface has increased. This UV-C may increase the rate of skin cancer, cataract & other UV rays related diseases.
In 1992, Canada introduced a UV rays indicator index, called UV index. It has no ranging from 1-11 which indicates the amount of UV rays present on the earth surface at day time. More the no more UV rays present.
WHO developed a chart for UVI
How does the Ozone layer protect the earth from ultraviolet radiation?
Ozone gas absorbs UV-B and becomes into two parts
- Oxygen molecule
- Oxygen atom
Later these two components again become Ozone molecules.
Another UV radiation UV-C is completely absorbed by oxygen in the stratosphere and UV-C splits an oxygen molecule into two oxygen atoms. These oxygen atoms again react with other oxygen molecules and produce ozone.
How ozone molecules are balanced at stratosphere?
In the stratosphere, other gases like nitrogen, hydrogen, etc react with ozone and convert it into oxygen molecules.
The balance of ozone production and destruction should be maintained for a healthy ozone concentration in the stratosphere.
But some human-produced chemicals (like CFC ) are disturbing the natural process of ozone production and destruction. As a result ozone concentration has decreased significantly at the stratosphere.
How Earth depends on the Sun
Continuous thermonuclear reactions are going on in the sun and yield a wide spectrum of radiation which radiates through space in all directions.
The sun radiant energy sustains all life on the earth. Solar energy maintains the temperature of the earth and it supports the growth of photosynthetic plants on the earth. These plants convert solar energy to chemical potential energy.
Human life’s eco-balance is completed with sunlight. So, sunlight is very much essential to sustain life on earth. But excessive solar radiation may be harmful.
How to protect skin from UV rays of the Sun
In the summer days, the intensity of UV rays is more, So we should be more conscious to come out from home. Protections should be taken to happily enjoy the great outdoors.
- Protecting your skin against UV exposure with Broad-Spectrum Sunscreen ( SPF at least 30) and with two hrs interval re-apply it.
- Apply sunscreen at least 15- 20min before go out.
- Eyewear. (Sunglass)
- Sun safe clothing, cover arms & legs (also use cap & umbrella)
What is SPF and how does it work?
The full form of SPF is Sun Protection Factor. This factor is the measure of UV rays pass-through sunscreen. Higher the SPF value less will be the UV rays pass-through screen.
Why UV radiation is more at noon?
More the distance travels through the atmosphere more will be the attenuation. At noon sunlight travels the least distance, so UV intensity on earth is more at noon.