Overexposure to mobile phone screens late at night can raise the risk of bowel cancer by as much as 60 per cent, a new study has warned.
Artificial light, also known as "blue light", emitted at night can also increase the likelihood of developing other health problems such as sleep disorders and obesity, according to researchers at the Barcelona Institute for Global Health.
Experts have previously linked blue light exposure at night with an increased chance of being diagnosed with breast and prostate cancer.
But now researchers say it heightens the risk of bowel cancer as well.
Bowel cancer, also known as colorectal or colon cancer, affects more than 250,000 people in the UK, and is the second most common cause of cancer death.
Study coordinator Dr Manolis Kogevinas, of the Barcelona Institute for Global Health, said: "Using the same methodology as the previous study, we decided to analyse the relationship between exposure to artificial light and colorectal cancer, the third most common type of cancer worldwide after lung and breast cancer."
Around 2,000 adults who lived in Barcelona and Madrid were surveyed for the study.
More than 650 pf them were found to have bowel cancer.
Watch: What is bowel cancer?
Using images from the International Space Station, authors were able to determine the level of blue light at night-time in areas across the two Spanish cities.
The way people behaved was not captured by the satellite images, for example using rolling shutters, which is common in Spain and other Mediterranean countries.
Researchers said residents in both cities, who lived in areas with the highest exposure to blue light, had a 60 per cent higher risk of developing colon cancer than those who were less exposed. Night shift workers were excluded from the study. Dr Kogevinas said blue light is emitted by most white LED lamps, tablets and mobile phone screens.
It produces a lot of energy but close exposure over a long period of time can suppress melatonin levels in the human body.
Melatonin plays a key role in regulating day-night cycles and has several other key functions. It is a powerful antioxidant and also has an anti-inflammatory function.
Experts suggest blue light may disrupt the body's circadian rhythm, which in turn affects hormone levels. Both breast and prostate cancers are hormone-related.
Dr Kogevinas said: "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."
It comes after previous studies indicated links between the technology included in LED street lighting and breast and prostate cancer.
In 2018, the Barcelona Institute for Global Health said an analysis of 4,000 people in 11 regions of Spain established a link between heavy exposure to LED lighting and a doubling of the risk of prostate cancer, as well as a 1.5-times higher chance of breast cancer.
It came after caution from health chiefs that LED street lights may disrupt people's sleep and damage eyesight. Public Health England had also raised concerns about the increasing use of LED lights on new cars.
The Barcelona Institute for Global Health's latest findings were published in the journal Epidemiology.