Though small amounts of ultraviolet (UV) rays are beneficial for people in treating several diseases and are essential in the production of vitamin D, prolonged human exposure to solar UV radiation may result in acute and chronic health effects on the skin, eye and the immune system.
According to American Cancer Society, exposure to ultraviolet radiation is a major risk factor for most skin cancers. Sunlight is the main source of UV rays. Tanning lamps and beds are also sources of UV rays. People who get a lot of UV exposure from these sources are at greater risk for skin cancer.
Even though UV rays make up only a very small portion of the sun’s rays, they are the main cause of the sun’s damaging effects on the skin. UV rays damage the DNA of skin cells. Skin cancers start when this damage affects the DNA of genes that control skin cell growth.
There are 3 main types of UV rays:
- UVA rays age skin cells and can damage their DNA. These rays are linked to long-term skin damage such as wrinkles, and they are also thought to play a role in some skin cancers. Most tanning beds give off large amounts of UVA, which has been found to increase skin cancer risk.
- UVB rays have slightly more energy than UVA rays. They can damage skin cells’ DNA directly, and are the main rays that cause sunburns. They are also thought to cause most skin cancers.
- UVC rays have more energy than the other types of UV rays, but they do not get through our atmosphere and are not in sunlight. They are not normally a cause of skin cancer.
- Both UVA and UVB rays can damage skin and cause skin cancer. UVB rays are a more potent cause of at least some skin cancers, but based on what is known today, there are no safe UV rays.
The strength of the UV rays reaching the ground depends on a number of factors, such as:
- Time of day: UV rays are strongest between 10 a.m. and 4 p.m.
- Season of the year: UV rays are stronger during the spring and summer months. This is less of a factor near the equator.
- Distance from the equator (latitude): UV exposure goes down as you get further from the equator.
- Altitude: More UV rays reach the ground at higher elevations.
- Cloud cover: The effect of clouds can vary. Sometimes cloud cover blocks some UV from the sun and lowers UV exposure, while some types of clouds can reflect UV and can increase UV exposure. What is important to know is that UV rays can get through, even on a cloudy day.
- Reflection off surfaces: UV rays can bounce off surfaces like water, sand, snow, pavement, or grass, leading to an increase in UV exposure.
(Read the full part of this article in the March Issue of Safety Messenger Magazine 2016)