UV Rays: What Should I Know?
What is UVA vs. UVB?
The sun actually produces three types of ultraviolet (UV) rays: UVA,UVBand UVC. UVC has the shortest wavelengths and is absorbed by the ozone layer before reaching earth. UVA and UVB rays both make it to earth and both contribute to skin damage and skin cancer.
How are these harmful?**UVA-** Most of the sun’s radiation that reaches the earth is in the form of UVA rays. These are less intense than UVB rays but are much more prevalent. UVA rays are responsible for the tanning of the skin, working to penetrate deep into the skin which can also causeskin aging and wrinkles. These rays can damage the basal layer of the skin and can contribute to皮肤癌. UVA rays can penetrate glass, which is why you are still at risk when indoors near a window or in a car.
UVB-While UVA makes your skin tan, it is UVB rays that cause sunburns. These rays don’t reach as far into the skin but also contribute to skin cancer. UVB rays are strongest between the hours of 10:00 AM and 4:00 PM. They can bounce off reflective surfaces, such as water, snow and ice, so they can cause damage to your skin from different directions. These rays do not penetrate through glass.
How does sunscreen work against these rays?
There are two types ofsunscreen: chemical and physical. Chemical sunscreens create a thin, protective film on the surface of the skin. This film absorbs UV radiation before it penetrates the skin. Physical sunscreens contain insoluble particles that reflect UV rays away from the skin. Most sunscreens sold today contain a combination of chemical and physical properties to provide you with both types of protection.
What’s up with SPF?SPFstands forsun protection factor. The number associated with the SPF indicates how long it takes for the UVB rays from the sun to redden your skin while wearing sunscreen, compared to how long it would take if you weren’t wearing it. For example, if you were using a sunscreen with an SPF 30, it would take 30 times longer to redden the skin than it would if you were not wearing sunscreen.
Does wearing sunscreen prevent me from getting my daily dose of vitamin D via the sun?
Vitamin D是一个重要的营养我们的身体需要合适的吗ly absorb calcium. Our bodies produce vitamin D when exposed to UVB rays from the sun. There has been some controversy over whether consistently using sunscreen to protect from UVB rays prevents the body from making the needed vitamin D.
Because it doesn’t require much sunlight to produce vitamin D, some doctors suggest being in the sun 10 to 15 minutes without sunscreen; however, many believe that isn’t necessary. According toHarvard Health, sunscreen probably doesn’t completely block UVB rays because most people do not put on adequate amounts of sunscreen or do irregularly.
Astudy completed at King’s College Londoncompared levels of vitamin D between people who applied sunscreen and those that did not and found there was not a significant difference. That would indicate our bodies produce vitamin D even with sunscreen applied.
