With the new expansion of Indoor Horticulture, we are seeing tremendous leaps forward in the lighting field. No longer are the days of mercury vapor lamps and simple wavelengths. We are now seeing complex lights focused on energy efficiency and Photosynthetic Active Radiation (PAR). PAR is the set of specific light waves that trigger biological responses. Growers are relying on Photosynthetic Photon Flux (PPF) and Photosynthetic Photon Flux Density (PPFD) to control every aspect of their lighting operation. While this is wonderful for producing highly efficient horticulture, it is potentially putting the human body in a very harmful environment. The time spent under the ever increasing light spectrum is extending due to indoor cultivation and product demands. The categories of ultraviolet, visible and infrared light all have health risks that should be recognized and accounted for.

Artificial light is composed of visible light as well as some UV and infrared (IR) radiations, and there is a concern that the emission levels of some lamps could be harmful for the skin and the eyes. Both natural and artificial light can also disrupt the human body clock and the hormonal system, and this can cause health problems. The ultraviolet and the blue components of light have the greatest potential to cause harm. As we are now entering the complete light frequency spectrum, we will physically be altered by these environments. A growing body of evidence suggests that environmental levels of UV radiation may suppress cell-mediated immunity (the body’s immune response that does not involve antibodies, but rather involves the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen). This suppression enhances the risk of infectious diseases and limits the efficacy of vaccinations.http://copublications.greenfacts.org/en/artificial-light/l-2/1-concerns.htm#0

Some people with diseases that make them sensitive to light claim that the energy-saving lamps (mainly compact fluorescent lamps (CFLs) and light emitting diodes (LEDs)) that have been brought to replace incandescent lamps, make their symptoms worse and play a role in a wide range of diseases. They also argue that protective measures such as covering the lamps with a second glass envelope (which decreases the UV-emissions), are ineffective.

Radiation levels decrease with distance to the lamp, so to ensure the lamps safety for the eyes and skin they are tested in the worst case scenario of the lamp being at a distance of only 20 cm. Based on these standard tests the lamps were classified into four Risk Groups: “exempt from risk” (RG0), “low risk” (RG1), “medium risk” (RG2), and “high risk” (RG3) which includes only lamps where a short-term exposure poses a threat. Considering the average time and space workers spend from the lights inside indoor horticulture environments, most lamps would be classified as RG2 or RG3.http://copublications.greenfacts.org/en/artificial-light/l-2/1-concerns.htm#0

The sun and lamps emit visible light and invisible radiations (UV and IR). The wavelength of visible light determines its color, from violet (shorter wavelength) through to red (longer wavelength). UV and IR can be subdivided according to their wavelength into narrower bands (UVA/UVB/UVC for ultraviolet, with UVA being the closest to visible light, and IRA/IRB/IRC for infrared, with IRA being the closest to visible light). The sun emits radiation over the full range of wavelengths, but the earth’s atmosphere blocks a lot of UVC and infrared radiations.

When light illuminates matter it can heat it up, and this is the main effect of IR. Visible and UV light can also start chemical reactions if they reach appropriate absorbing molecules called chromophores, and these are very abundant in skin and eye cells. Visible and IRA radiations penetrate deepest into the skin and eye and can reach as far as the retina. UVC, IRB and IRC penetrate the least.https://www.ishn.com/articles/94815-dangers-of-overexposure-to-ultraviolet-infrared-and-high-energy-visible-light

A simple comparison would be between tanning bed lights, which operate between 100-400 watts, while grow lights are on average between 300-1,000 watts, and can go higher. The average tanning bed produces approximately the same amount of UVB light as the sun and upwards of three times the amount of UVA light (source: Harvard Medical School). Indoor UV lighting operates in a similar fashion in regards to increasing UV bursts to maximize biological responses. While the desired goal is a biological response from plants, any biological entity will also be affected (i.e. human body). When working in indoor facilities you increase the UV radiation one is exposed to due to the concentrated bursts in confined spaces. This causes faster mutations as the ultraviolet light changes your skin and body on a molecular level, thereby altering the configuration of your DNA. With the average grow light producing exponentially more wattage than a tanning bed, it is imperative that those working under these conditions have the necessary protection provided to them to ensure a healthier future, and greatly reduce the harmful cancerous affects.