What is UV?

The sun gives off ultraviolet radiation that we divide into categories based on the wavelength There are three types of UV radiation in the environment:

The UV Index is a public health education tool supported by the EPA and reported by meteorologists in 58 U.S. cities. It offers a daily report of UV light levels on a scale from 1-10+. You can search for your index here http://www.epa.gov/sunwise/uvindex.html

The World Health Organization has quality reference information on UV effects and can be found at http://www.who.int/uv/en/

UVC UVC radiation is almost completely absorbed by the ozone layer and does not affect the skin. UVC radiation can be found in artificial sources such as mercury arc lamps and germicidal lamps. UVB UVB is mostly absorbed by ozone. UVB rays penetrate the outer layer of the skin and cause sunburn. UVB is a medium wavelength ultraviolet ray from the sun. UVB rays are the "burning" rays in the UV spectrum. UVB radiation ranges from 280 to 320 nm in wavelength. Some wavelengths in that range have greater potential to cause damage than other wavelengths. UVB radiation is stronger between late morning and early afternoon when the sun's rays are directed straight down at the Earth. UVA UVA is not absorbed by the ozone. UVA rays penetrate more deeply into the skin and are responsible for 90% of the damage that cause premature aging. UVA is a long wavelength ultraviolet ray from the sun. UVA rays are the"aging" rays in the UV spectrum. UVA radiation ranges from 320 to 400 nm in wavelength. Some wavelengths in that range have greater potential to cause damage than other wavelengths. UVA radiation is stronger in the early morning and late afternoon when the sun's rays reach the Earth at an angle.

Types of Electromangnetic Radiation

SPF vs. UPF

What is SPF?

SPF stands for Sun Protection Factor. The number is determined experimentally indoors by exposing human subjects to a light spectrum meant to mimic noontime sun. Some subjects wear sunscreen and others do not. The amount of light that induces redness in sunscreen-protected skin, divided by the amount of light that induces redness in unprotected skin is the SPF. It is mainly a measure of UVB protection and ranges from 1 to 45 or above.

A sunscreen with an SPF of 15 filters 92% of the UVB. Put another way, a sunscreen with an SPF of 15 will delay the onset of sunburn in a person who would otherwise burn in 10 minutes to burn in 150 minutes. The SPF 15 sunscreen allows a person to stay out in the sun 15 times longer.

There is currently no uniform measure of UVA absorption. There are broad-spectrum sunscreens that protect against UVA and UVB radiation although it is important to remember that the SPF does not predict UVA protection.

What is UPF?

UPF stands for Ultraviolet Protection Factor. This new rating system for clothing called the Ultraviolet Protection Factor, or UPF, was developed to specifically measure a fabricís ability to guard unprotected skin from the UVA and UVB rays. 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. Hence UPF values are used in the Fabric's UV transmittance test by spectrophotometer equipment.

Sun Protective Clothing

Sun protective clothing is any garment that can provide adequate protection from the sun. Generally speaking, clothing must have a UPF value of 15 to 50+ (blocks 93 - 98% of UV radiation), and cover or shade sufficient skin to protect a person from the damaging rays of the sun.

The following are some UPF ratings and the UV protection they provide:

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