Spanish Study Concludes that Exposure to Blue Light, from Mobile Phones, Increases the Risk of Colorectal Cancer

In 2018, researchers at the Barcelona Institute for Global Health observed that high levels of exposure to light at night in the blue-enriched light spectrum doubled the risk of prostate cancer and increased the risk of breast cancer 1.5-fold, in a sample of 4,000 people across 11 regions of Spain.[i]

Artificial blue light is emitted by light emitting diodes (LED), technology which is typically incorporated into mobile phone, tablet and television screen panels, as well as streetlamps and automotive headlights.

Using the same methodology as the 2018 study, the Institute for Global Health diversified its focus to analyse whether overexposure of this kind is also associated with cancers of the colon and rectum, i.e. colorectal cancer (otherwise known as bowel cancer).

A case-control study was devised, assigning participants to their geocoded longest residence in Madrid/Barcelona and measuring exposure to ‘blue light’ at night during sleeping time, based on International Space Station (Earth Science and Remote Sensing Unit, NASA Johnson Space Centre) imaging.[ii]

Results have been produced twice in the past 2-years, with similar conclusions.

The 1st academic paper cited the inclusion of 528 patients with histologically confirmed colorectal cancer and 960 controls.[iii] The 2nd and most recent paper, published in the Epidemiology journal in September, alluded to 661 patients with histologically confirmed colorectal cancer and 1,322 controls.[iv] None of the study participants had ever worked at night.

For patients living in areas with heightened ‘blue light’ exposure, the earlier publication noted an 89% increase in risk of developing colorectal cancer, while the latest paper documented a 60% increase in risk.

Why might blue-enriched light have this effect on the human body?

Well, long-term exposure is known to suppress hormone (specifically melatonin) levels, potentially by disrupting the body’s circadian rhythm.[v]

Incidentally, cancers of the breast and prostate happen to be hormone-related.

Given that melatonin is also responsible for regulating day-night cycles and performing antioxidative and anti-inflammatory functions, it is understandable why experts have tied exposure to LED light with sleep disorders and obesity. What is more, Public Health England (PHE) previously warned that those exposed to LED lighting may suffer retinal damage, headaches, migraines and feelings of malaise.[vi]

Reflecting on the conclusions of the 2020 journal article, Lead Author and Head of the Institute’s Cancer Programme, Dr. Manolis Kogevinas, appraised that:

‘Night-time exposure to light, especially blue-spectrum light, can decrease the production and secretion of melatonin, depending on the intensity and wavelength of the light.

There is growing concern about the effects of light on ecosystems and human health. Research on the potential effects of light exposure is still in its infancy, so more work is needed to provide sound, evidence-based recommendations to prevent adverse outcomes’.[vii]

When we analysed rising incidence of colorectal cancer among asbestos exposed workers, in edition 303 of BC Disease News (here), we revealed that it is the 4th most commonly diagnosed cancer sub-type and, affecting around 42,300 people every year. It is also the 2nd most common cause of cancer mortality, resulting in around 16,300 deaths per year.[viii]

What impact will the growing influence of LED technology in our modern lives have on these statistics moving forwards? Only time will tell.


[i] Garcia-Saenz et al., Evaluating the Association between Artificial Light-at-Night Exposure and Breast and Prostate Cancer Risk in Spain (MCC-Spain Study). Environ Health Perspect. 2018 Apr 23;126(4):047011. <> accessed 14 October 2020.

[ii] (NASA) <> accessed 14 October 2020.

[iii] Garcia-Saenz A et al., Artificial light at night (ALAN), blue light spectrum exposure and colorectal cancer risk in Spain (MCC-Spain study). Environmental Epidemiology: October 2019 - Volume 3 - Issue - p 212 <,_blue_light.646.aspx> accessed 14 October 2020.

[iv] Garcia-Saenz A et al., Association Between Outdoor Light-at-night Exposure and Colorectal Cancer in Spain. Epidemiology: September 2020 - Volume 31 - Issue 5 - p 718-727. <> accessed 14 October 2020.

[v] ‘What is blue light? The effect blue light has on your sleep and more’ (7 July 2020 Harvard University) <> accessed 14 October 2020.

[vi] ‘Public Health England issues LED street lighting warning’ (3 April 2018 Highways Magazine) <> accessed 14 October 2020.

[vii] ‘Exposure to mobile phone light at night raises risk of bowel cancer’ (30 July 2020 The Telegraph)  <> accessed 14 October 2020.

[viii] ‘Bowel cancer statistics’ (Cancer Research UK) <> accessed 14 October 2020.