Smartphones emit several types of electromagnetic fields that can harm our health. In addition to harmful radio-frequency radiation, they also emit blue light. While humans have always been exposed to natural blue light frequencies in nature, our use of smartphones and screens has resulted in unprecedented exponentially increased exposures at all hours of the day and night.

A 2020 study on colorectal cancer and blue light at night with over 2000 subjects found outdoor blue light at night is linked to colon cancer. Watch a video from the scientist below.

The study

Garcia-Saenz, Ariadnaa–c; de Miguel, Alejandro Sánchezd–g; Espinosa, Anaa–c,h; Costas, Laurab,i; Aragonés, Nuriab,k; Tonne, Cathryna–c; Moreno, Victorb,i,j,l; Pérez-Gómez, Beatrizb,m; Valentin, Antoniaa,c,h; Pollán, Marinab,m; Castaño-Vinyals, Gemmaa–c,h; Aubé, Martinf; Kogevinas, Manolisa–c,h Association Between Outdoor Light-at-night Exposure and Colorectal Cancer in Spain, Epidemiology: September 2020 – Volume 31 – Issue 5 – p 718-727
doi: 10.1097/EDE.0000000000001226

We investigated the association between exposure to ALAN according to light spectrum and colorectal cancer among subjects who had never worked at night in a general population case–control study in Spain.
Exposure to blue light spectrum was positively associated with colorectal cancer (OR = 1.6; 95% CI: 1.2–2.2; highest vs. lowest tertile).
Outdoor blue light spectrum exposure that is increasingly prevalent in recent years may be associated with colorectal cancer risk.
See video abstract: http://links.lww.com/EDE/B708.

Artificial blue light can damage the eyes, contribute to aging of the skin and harm our sleep. It is linked to depression and mental health problems.

Research on animals

“To understand why shining the blue light at the mice led to depression, the researchers studied their brains—most specifically, the neural pathways that lead from the eyes to the brain. They found a specific kind of light receptor in the mouse retina that led to brain areas associated with mood: the nucleus accumbens and the dorsal perihabenular nucleus. When the researchers disconnected them, the mice did not become depressive due to exposure to blue light at night. The researchers also found that the pathways became much more active when processing blue light at night versus daytime—which, they suggest, explains why blue light during the day does not lead to depression.” -Medical Express “Exposing Mice to Blue light Leads to Depressive Symptoms”

science to know

Meng Q , Lian Y , Jiang J , et al. Blue light filtered white light induces depression-like responses and temporary spatial learning deficits in rats. Photochem Photobiol Sci. 2018;17(4):386-394. doi:10.1039/c7pp00271h

Blue filtered light induces depression-like symptoms and temporary spatial learning deficits in rats, which might be closely related to the impairment of light-evoked output signals in the retina.

Heo JY, Kim K, Fava M, et al. Effects of smartphone use with and without blue light at night in healthy adults: A randomized, double-blind, cross-over, placebo-controlled comparison. J Psychiatr Res. 2017;87:61-70. doi:10.1016/j.jpsychires.2016.12.010

“This study investigated the immediate effects of smartphone blue light LED on humans at night. We investigated changes in serum melatonin levels, cortisol levels, body temperature, and psychiatric measures with a randomized, double-blind, cross-over, placebo-controlled design…”
“use of blue light smartphones was associated with significantly decreased sleepiness (Cohen’s d = 0.49, Z = 43.50, p = 0.04) and confusion-bewilderment (Cohen’s d = 0.53, Z = 39.00, p = 0.02), and increased commission error “

Nakashima Y, Ohta S, Wolf AM. Blue light-induced oxidative stress in live skin. Free Radic Biol Med. 2017;108:300-310. doi:10.1016/j.freeradbiomed.2017.03.010

Exposing human skin to the blue light contained in sunlight depressed flavin autofluorescence, demonstrating that the visible component of sunlight has a physiologically significant effect on human skin. The ROS produced by blue light is probably superoxide, but not singlet oxygen. These results suggest that blue light contributes to skin aging similar to UVA.

Janků K, Šmotek M, Fárková E, Kopřivová J. Block the light and sleep well: Evening blue light filtration as a part of cognitive behavioral therapy for insomnia. Chronobiol Int. 2020;37(2):248-259. doi:10.1080/07420528.2019.1692859

We provide further evidence that blocking short-wavelength light in the evening hours may be beneficial for patients suffering from insomnia.

Safety at Home

Reduce the Blue Light From All Screens

Blue light is well understood to impact our sleep and worse, it can damage the eyes, especially children’s eyes as they are more vulnerable. Light at night is linked to cancer and can cause or worsen many health problems because it robs us of the natural healing that happens during deep sleep. Many health authorities recommend we eliminate and reduce blue light to protect our health. Practical steps include:

Use a blue light blocker covering for all your computer/laptop/tablet screens including cell phones.
Use blue-blocking glasses when you are working on the computer (This does not protect the skin.)
Some people will use a blue light blocker (which is a thin film that sits unnoticeable over the screen) and then also a 100% blue blocker of hard thick plastic at night. However, be aware that many of the thinner unnoticeable blue light coverings on the market do not protect 100% blue light.
Download a program (like Iris) onto your device that will automatically reduce blue light at night.

Shopping list

Support our nonprofit by shopping with these affiliate links. This allows us to continue to spread awareness and provide resources. We only share items that EHT staff uses.