Most grow lights on the market are manufactured for specific wavelengths targeting different stages of plant growth: red Light Emitting Diodes (LEDs) activate seed, root, flower and fruit production; blue LEDs make strong stems and roots; and both have a strong role in active photosynthesis. On the other hand, plants also need yellow light, like that produced by High Pressure Sodium (HPS) fixtures, for photorespiration, or the growth stage where plants consume most of their nutrients. Though many growers use HPS and other combinations of light sources successfully, new full-spectrum LEDs are becoming more available as an energy-efficient and economical choice for high-yield grows.
Full-spectrum LEDs and UV radiation
Why should growers consider full-spectrum LEDs? LEDs utilizing the full light spectrum replicate the effects of natural sunlight more closely than other artificial light sources. When the entire light spectrum is available to plants, they can differentiate between each targeted light spectrums, which we see as colors, for higher absorption and cellular activation. The full spectrum that includes rays both visible and invisible to the human eye appear white in color when active simultaneously. Though the white, sun-like conditions make it easier to see normal colors with the naked eye (as opposed to traditional LEDs that appear pink or purple, or HPS lights that appear yellow), the highest risks of eye and skin damage exist in the invisible UV rays emitted by these lights. Later, we’ll mention the potential risk of visible blue light that’s also present in these types of fixtures.
Any artificial light used for indoor growing emits a certain amount of UV-A and UV-B Radiation by default, since these rays are what contribute to photosynthesis in natural sunlight. Almost anyone who’s ever worn sunblock is familiar with UV-A and UV-B, the most well-known types of UV radiation emitted by the sun. A third type of UV Radiation, UV-C, is also present in natural light but is almost 100 per cent absorbed by the Earth’s atmosphere. With artificial light, particularly full-spectrum LEDs, there is a high probability of UV-A and UV-B Radiation, but also potential exposure to UV-C Radiation, which poses the most serious risks to eye and skin health.
UV light and cataract formation
According to the Journal of Environmental Health Perspectives, “Ultraviolet light exposure to the eye has been associated with cataract formation and retinal degeneration. In both cases, it is hypothesized that ultraviolet light can initiate formation of free radicals, which can cause protein modification and lipid peroxidation.” In short, the UV Radiation emitted by full-spectrum LEDs may pose a higher risk to eye health than other types of artificial light, and those exposed should always protect their eyes from these harmful rays.
High-energy visible light — blue light
We’ve touched on the risks of exposure to UV light and explained why utilizing the full-spectrum of light may be beneficial for plant growth. But between lower-energy visible light and high-energy UV light, there is blue light, also known as High-Energy Visible (HEV) light. There’s a lot of information circulating about HEV light due to increased use of computers, cell phones, and other devices emitting blue light. Full-spectrum LEDs are certainly one of these devices.
Though the risks of eye exposure to HEV light may not be as damaging as UV light, it can have adverse affects on your overall health. While UV light can damage the cells of the eye and lead to degenerative eye diseases over time, HEV light affects hormone balance and fatigue, particularly due to its effect on melatonin levels, which regulate alertness and sleep cycles. From the Harvard Health Letter, 2012: “While light of any kind can suppress the secretion of melatonin, blue light...does so more powerfully. Harvard researchers and their colleagues conducted an experiment comparing the effects of 6.5 hours of exposure to blue light to exposure to green light of comparable brightness. The blue light suppressed melatonin for about twice as long as the green light.” This imbalance may be why those who spend extended periods of time exposed to artificial light, such as indoor horticulturists, experience unwanted fatigue, headaches, eye pain, or trouble sleeping.
Here’s the takeaway: LEDs have always been an efficient choice, producing less heat and taking up less space than other light sources. Though they may pose a higher initial investment, they tend to last longer and have a lower environmental impact than HPS or Ceramic Metal Halide lights, though these lights are still widely used with great success in indoor grows. No matter what light source growers ultimately choose, these technologically advanced devices can pose risks. Knowing the risks can help you make an informed decision about protecting your eyes in these conditions. Always wear protective eyewear that shields UV Radiation to protect your eyes from long-term damage. Choose eyewear that balances color and provides clear vision, so you can accurately assess your plants. Many products that protect your eyes from UV light and HEV light may be an economical solution but don’t provide visual clarity that protects against eye strain and fatigue. Keep your plants and your eyes healthy for life.