Skin cancer occurs when skin cells are damaged, for example, by overexposure to Ultraviolet (UV) radiation from the sun. Australia, due to the geographic position of the country and the way of life is at the forefront of this problem.
Every year in Australia :
• Skin cancers account for around 80% of all newly diagnosed cancers
• Between 95 and 99% of skin cancers are caused by exposure to the sun
• There are more than 1 million patient consultations per year for skin cancer
• Two in three Australians will be diagnosed with skin cancer by the time they are 70.
This problem is not limited to Australia. For instance, the UK sees a rise in skin cancer that is explained by the increase of UK people spending holidays in South Europe and spending too much time in the sun.
The only way to reduce the number of skin cancer incidences is to spend less time in the sun. More and more wearables integrate a UV sensor that gives the UV index in order to warn people they spent too much time in the sun.
What is the UV Index?
The UV index is a number linearly related to the intensity of sunburn-producing UV radiation at a given point on the earth’s surface. It cannot be simply related to the irradiance (measured in W/m2). The UV region covers the wavelength range 100-400nm and is divided into three bands
• UVA (315-400 nm)
• UVB (280-315 nm)
• UVC (100-280nm)
As sunlight passes through the atmosphere, all UVC and approximately 90% of UVB radiation is absorbed by ozone, water vapor, oxygen and carbon dioxide. UVA is less affected by the atmosphere. Therefore, the UV radiation reaching the Earth’s surface is largely composed of UVA with a small UVB component.
The typical incident power density in midday summer sunlight is typically 0.6mW/(nm m2) at 295nm, 74mW(nm m2) at 305 nm and 478 mW/(nm m2) at 325 nm. The shorter the wavelength is, the more damaging it is for the skin. For the same irradiance, 305nm is 22% as damaging as 295nm and 325nm is 0.3% as damaging as 295nm. Hence the erythemal weighting factors are 1.0, 0.2 and 0.003 respectively. The weight to give each wavelength is determined by these two equations:
Integration of these values using all the intermediate weightings over the full spectral range of 290nm to 400nm produces a figure of 264mW/m2, which then divided by 25 mW/m2 to give a UV index of 10.6. Hence, UV is most of the time a value between 0 and 11 and a simple UV index can determine the irsk of harm from unprotected sun exposure for the average adult. 0-3 is low, unlike 8 to 10 (that is very high risk).
So instead of pulling out your calculator and doing some intense math to figure out if you’re at risk of a sunburn, smart clothing manufacturers have started to integrate UV sensors into their products. These UV sensors can give you an alert when the sun is at its strongest and let you know when you’ve had enough of the sun’s harsh rays.
Currently on the market are the Vishay VEML607, Silicon Labs Si114x or STMicroelectronics UVIS25, all of which are small UV index sensors that are a perfect fit for designs in wearables.