Light Exposure at Night.

Recent research shows that the harmful effects of light at night are largely mediated by certain blue wavelengths which are detected by newly-discovered melanopsin photoreceptors in the retina ganglion cells in the eye.

Blue Wavelengths are Responsible for the Harmful Effects of Light at Night

Light falling on the human eye serves at least two distinct functions. The most obvious function is vision, using the rods and cones in the retina to see images of the world. A second and less well-known function is the non-image forming “time-keeping” connection that regulates the activity of biological clocks, important brain hormones, and certain aspects of behaviour.

The time-keeping pathway involves a different set of cells in the retina of the eye with a different photopigment (melanopsin) that is especially sensitive to blue light.

This pathway directly feeds into a biological clock in the brain (the “suprachiasmatic nucleus” or “SCN”) which is responsible for generating circadian rhythms.  When the time-keeping pathway is activated by these wavelengths of blue light, it triggers the SCN to regulate specific hormones such as melatonin and cortisol.

Melatonin released by the pineal gland is a critical suppressor of tumour growth. Cortisol, the so-called “stress hormone,” is a master molecule that influences many other critical hormones including insulin which regulate the body’s health and metabolism. Normal sleep, restfulness, alertness, and health are orchestrated by these and other molecules in exquisitely precise rhythms in response to the cycles of light and darkness.

Blue light during the day is critical to synchronizing our circadian rhythms, but we are not designed to see blue light at night. Many of the adverse effects of chronic light exposure at night appear to be mediated by abnormal night time stimulation of this time-keeping pathway by the blue light wavelengths in the light spectrum. When this pathway is disrupted by exposure to white light or only blue light at night, it initiates a chain reaction that results in decreased energy, mood, performance and vigilance and increased risk of errors, accidents, injuries, absenteeism and workplace turnover. Over the long- term, continuous light exposure at night results in sustained hormonal dysregulation leading to significant health consequences including sleep disorders, diabetes, heart disease, depression and even certain types of cancer (e.g., breast, prostate and colon cancers).

Conventional Blue-Pump LED Lighting Exacerbates the Harmful Effects of Light at Night.

(Left) Conventional LEDs are far more energy efficient and will rapidly gain market share. (Right) As the blue-pump LED market share increases the relative nocturnal light exposure risk can be expected increase steeply.

Neither current conventional lighting systems, nor the newly emerging blue-pump LED luminaries prevent the adverse health, safety and productivity impact of light exposure at night.

Indeed, the reliance of the LED lighting revolution on cheap blue-pump LEDs may exacerbate the health, safety and productivity issues associated with nocturnal light exposure. All conventional white light sources (incandescent, halogen, fluorescent), when used at night show the harmful effects, but the effects are particularly exacerbated by the use of blue pump LEDs. The highly efficient and low cost conventional LED chips have a LED chip which delivers a blue light intensity spike which is highly suppressive of melatonin.  The amount of blue light emitted is substantially greater in these LEDs as compared to incandescent bulbs, fluorescent lights or CCFLs.

The $5 billion US market and more than $50 billion global market for industrial and commercial lighting is in the middle of a major transition from incandescent and fluorescent lighting to LED lighting, driven by the significant improvement in energy efficiency (lumens per watt), the reduced lifetime cost of LED lighting (LCOL), and the opportunity to integrate smart lighting controls. By 2020 LED lighting is projected to achieve a 46% penetration of the market for industrial and commercial lamps. Philips projects 75% of commercial lighting will be LED- based by 2030. According to Philips, 51% of the total lighting energy consumption in the US is industrial and commercial. Government energy conservation policy and business economics will drive the replacement of current lighting by LED sources.

A similar trajectory is expected for the consumer and residential market. No longer is there a price barrier to LEDs evidenced from the recent arrival of cheap bulbs in retail stores.

The health issues relate to nocturnal light exposure may well worsen into an epidemic as the use of these conventional blue-pump LEDs with potent melatonin suppression and neuroendocrine disruptive properties sweeps through industrial and commercial and retail workplaces, and the even larger consumer household marketplace.