The spectral irradiance of sunlight depends on longitude, latitude, altitude, time, weather, pollution, the stratosphere, and the immediate environment.
Skin damage from UVB is higher than from UVA -- a sensitivity known as the "erythema spectrum." This response was adopted by the WHO and the EPA to create the UV index, the health relevant unit of UV radiation that includes skin biology.
Several sensor companies have tried to market general-purpose UV photodiodes as UV Index sensors but these sensors do not replicate the erythema spectrum. As a result, they perform poorly when measuring the UV index in sunlight conditions.
Someone's immediate environment drives UV risk. For example a car window will block UVB but not UVA, which the real-time UV index will reflect.
In use, 90% of the time, people are exposed to low-strength UV rays. Low UV performance is the foundation that builds trust and understanding.
Shade measures cumulative UV exposure and can be used to provide alerts prior to overexposure, so that inattention does not lead to bad surprises.
Recent studies have shown that sunscreen's active ingredients are absorbed in the bloodstream. However, the safety profile of these ingredients in the bloodstream has never been evaluated.
FDA is now encouraging consumers to use other methods of sun protection.
We have developed & patented a novel way to measure the UV index in wearable devices.