Do Street Lights Trigger Breast Cancer?

Breast cancer is the most common type of cancer in women. In the development of breast cancer; It is thought that genetic factors, poor quality foods, malnutrition and obesity, low physical activity, as well as environmental factors may be triggers in the development of cancer. 

Recent studies have shown that one of these environmental factors may be overexposure to artificial nighttime lighting, which is little known in the community.

To briefly mention some of these studies;

In a study published in June 2020, street lighting light levels of 186,981 women living in the same place for the last 16 years were examined according to satellite data.

Street lighting level was divided into 4 stages and a comparison was made. It was determined that the breast cancer risk of those living in the areas with the most intense lighting (Level 4) increased by 10% compared to those living in the least intense area (Level 1). This difference is particularly evident among women who have gone through menopause.

In a study conducted in South Korea and published in 2015, it was found that the risk of breast cancer is higher in women living in settlements with the highest night light pollution compared to other regions, but the risk of lung, bowel, stomach, cervix and liver cancer did not differ.

Why is breast cancer more common in those exposed to more artificial night light?

80% of the world's population (99% of the population of Europe and North America) and about one-fifth of the world's surface area has light pollution, mostly from street lighting. Decorative lights in places such as street lamps, billboards, security lights, shopping malls are other artificial light sources outside the residence. According to the evaluations, city lights create 200,000 times more luminosity than a moonlit sky night.

Animal and epidemiological studies have shown that exposure to light at night (ALAN) disrupts the daily circadian rhythm in the body and reduces melatonin secretion at night. This decrease is thought to increase the risk of breast cancer by disrupting the estrogen balance.

Artificial night light, which has a different structure compared to natural night light, can trigger breast cancer in women with its negative effect on melatonin secreted from the brain at night. In a study, findings were found that it also triggers the development of prostate cancer in men. For this reason, we should not forget that staying awake until late at night, dealing with work, spending long hours in front of the television-computer, sleeping in bedrooms with television, mobile phone or other electronic or electrical appliances that give light pose a risk in terms of breast cancer.

Prof. Hakan Karagöl, MD.
Medical Oncologist