- Sun protection factor (SPF)
-
Sun protection factor (SPF) is a number on sunscreen labels that indicates
how long skin can be in the sun and maintain a low risk for sunburn.
The higher the SPF number, the longer it protects a person from burning
rays.
The Sun Protection Factor (SPF) rating applies only to protection
from ultraviolet B (UVB) rays. Some sunscreens protect against UVA rays,
but they have no SPF rating. No sunscreen gives total protection, but “broad-spectrum” sunscreens
that contain ingredients such as avobenzone, benzophenones, cinnamates,
salicylates, sulisobenzone, titanium dioxide, and zinc oxide usually protect
from UVA and UVB rays.
- What is UPF?
-
UPF stands for Ultraviolet Protection Factor. It is the ratio of
the average effective ultraviolet radiation (UVR) irradiance transmitted
and calculated through air to the average effective UVR irradiance transmitted
and calculated through fabric. In other words, it is the amount of ultraviolet
radiation that a fabric blocks. Fabrics are generally tested by spectrophotometer
equipment and are not tested using human subjects. Hence UPF values are
used since the endpoint of the test is UV transmittance, not skin reddening.
Sunu Protection Factor (SPF) values indicate a function of skin reddening,
therefore only fabrics tested on human subjects should use a SPF value.
- UV Rays: What are they?
- UVA is a long wavelength that penetrates the skin very deeply,
degrading the elastic fibers in the skin. This causes aging, some
sunburn and adds to the effect of UVB rays.
- UVB rays penetrate the top layers of the skin creating sunburn.
This sunburn promotes skin aging and is the main cause of skin
carcinomas.
Exposure to UVA and UVB rays has a cumulative effect on the body. The
more exposure, the more potential damage is done
Regardless of colour, skin responds that is repeatedly exposed to the sun tends to become tough and thick. The results can be leathery skin with wrinkles beyond the middle years of adulthood. What can help is using a sunscreen product with a high degree of protection from UV rays, listed as the concentration on the SPF (Sun Protection Factor) numbers on the products’ labels. These sunscreen products can be made with ingredients that offer protection against UVA rays and / or other ingredients to protect against UVB rays (more harmful for sun burning than UVA rays.) The best products offer ingredients for protection from both UVA and UVB rays.
The Sun Protection Factor (SPF) listed on the product label
refers to the minimum amount of UVB sunlight required with that
product in order for redness to appear on the skin after that
product has been applied, versus the length of time bare skin
or skin without the product applied would redden. To sum that
up, the basic math involved in using the SPF number is like this.
The Sun Protection Factor (SPF) number tells people how much
longer they can last out in the sun with protection for their
skin without being burned. For example, say a young high school
student would normally burn after 12 minutes of being out in
the sun. He applies a sunscreen, also referred to as a sun block,
with an SPF of 15. This means that he should be fine for 15 times
his average amount of protection time. In other words, he would
be protected for up to 3 hours.
Here is the formula for calculating: 12 minutes x 15 SPF = 180
minutes (3 hours).
Note that regardless of skin type, before going out into the
sun’s rays, each person should have the most suitable sunscreen
product possible applied beforehand for protection against UV
rays. The product should be spread fairly thick and in a uniform
manner for the best possible UV protection over all areas of
the skin that will be exposed to the UV rays.
The table below will give an indication of the different UPF
protection ranges and the percentage of UV blocked.
Good UV Protection |
15-24 |
15 and 20 |
93.3% - 95.8% |
Very Good UV Protection |
25-39 |
25, 30 and 35 |
96.0% - 97.4% |
Excellent UV Protection |
40-50+ |
40, 45, 50 and 50+ |
97.5% - 98.0% |
|
