The answer is harmful. UV LED ultraviolet light source has good penetrating power, and we have been developing better ones!
Artificial UV light usually has stray light. UVA may include UVC, UVB, and UVV. Different wavelengths have different effects. UVC sterilization and UVB are beneficial to the growth of life. It is generally believed that ultraviolet rays are harmless. What is the harm to the sun? The sun's UVC is refracted by absorption and scattering, and does not reach the surface of the earth. UVA can usually peel off human skin. UVC can break bacterial DNA. Artificial UV light is used to meet industrial requirements, curing, sterilization, etc., if it is seen by the eyes For a long time, any wavelength of UV ultraviolet rays will definitely not work for the retina.
UV-B (280-315 nanometers, also called medium-wave ultraviolet), UV-C (100-280 nanometers, also called short-wave ultraviolet rays, are definitely harmful. Sunlight contains these, so it is very powerful in sunlight It is easy to damage the skin when UV-B and UV-C reach a certain amount, it will definitely harm the body, so protective measures must be taken.
As for UVA, it is less harmful to the body, especially the widely used wavelengths above 360nm. Human skin has a certain protective function, so it can be regarded as harmless to the human body. Of course you still can't shoot your eyes directly. Most UVLEDs used in printing have wavelengths above 360!
Of course, it is best to bring a UV glasses, or do a good shading protection!
At present, the printed UV LEDs are all UVA, single-wavelength, no ozone, relatively safe, but be careful not to look directly at the light source.