Modern street lamps and mobile phones are causing thousands of cancer cases, according to a new study.
A study by the University of Exeter found that men in metropolitan areas are twice as likely to develop prostate cancer as women are one and a half more susceptible to breast cancer.
Scientists cite the disturbing trend as the "blue light" of the LEDs. This reduces the melatonin level that controls the body's clock.
Both forms of the disease have been linked to a lack of hormone produced during sleep.
The disturbing findings also raise concern over blue light from smartphones and tablets, Devon Live reports.
In the UK, hundreds of thousands of street lamps have been replaced by LEDs that are cheaper and have less emissions.
Dr. Alejandro Sanchez de Miguel of the University of Exeter said: "Humans have evolved
" As cities replace the older lighting, we are all exposed to higher "blue" lights that can disturb our biological clocks. "
He said the same goes for outdoor lighting, such as as advertising
"It is imperative that we know for sure if this will increase our cancer risk.
"Scientists have long suspected that this could be the case – now our innovative results show a strong connection.
We also need to investigate if it is night Exposure to the blue light of smartphones and tablets increases ours Cancer risk. "
His team compared medical and epidemiological data from more than 4,000 men and women between the ages of 20 and 85 in 11 regions of Spain, mainly Madrid and Barcelona
The analysis, published by the Barcelona Institute for Global Health (ISGlobal) found that the blueer the city's light emission was, the higher the risk of cancer compared to those in suburban or rural areas.
Those who lived in houses with darker rooms, such as shutters, also showed a lower risk.
Older lighting concepts make a glow appear in the "orange" spectrum, but new modern lighting produces a bright "blue" emission.  The exposure of indoor spaces to artificial light was determined by personal questionnaires, with the outside levels being evaluated by night shots taken by astronauts aboard the International Space Station.
It was the first time that this happened