Artificial Light at night: A silent trigger for cancer?

Imagine walking through a city bathed in the warm glow of the street lights. Looks like a scene straight out of a romcom, right? Well, no matter how beautiful it looks, there is danger lurking. No, we aren’t talking about a thief eyeing your purse. But the street lights. While artificial light at night may seem harmless, growing research suggests it could have serious health consequences, including increasing your cancer risk. The invention of artificial lights has certainly played a crucial role in human evolution, civilization, and progression, but it's doing no good for your health. Studies now link nighttime exposure to artificial light with an increased risk of cancer.

The 2010 study conducted by researchers from the Center for Interdisciplinary Chronobiological Research at the University of Haifa, found a clear link between light at night and cancer. "Exposure to LAN– disrupts our biological clock and affects the cyclical rhythm that has developed over hundreds of millions of evolutionary years that were devoid of LAN. Light pollution as an environmental problem is gaining awareness around the world, and the World Health Organization's International Agency for Research on Cancer (IARC) has already classified working the night shift as a higher grade of cancer risk," the researchers noted.

A 2016 study has investigated the relationship between artificial light at night (ALAN) and cancer rates across 158 countries. The researchers found that higher levels of ALAN were associated with higher rates of all cancers, as well as the four most common types: lung, breast, colorectal, and prostate cancers.

A large long-term study from Harvard T.H. Chan School of Public Health has found that breast cancer risk may be higher for women who live in areas with high levels of outdoor light at night. "In our modern industrialized society, artificial lighting is nearly ubiquitous. Our results suggest that this widespread exposure to outdoor lights during nighttime hours could represent a novel risk factor for breast cancer," lead author Peter James said in a statement. The study published in Environmental Health Perspectives in 2017 found that women exposed to outdoor light at night had an increased 14 percent of breast cancer risk.

Another 2021 study published in CANCER, a peer-reviewed journal of the American Cancer Society, found that people living in regions with high levels of outdoor artificial light at night may face a higher risk of developing thyroid cancer. The scientists noted that light at night suppresses melatonin, a modulator of estrogen activity that may have important anti-tumor effects. Lights at night may lead to disruption of the body's internal clock known as circadian rhythms, which is a risk factor for various types of cancer.

While lights at night have become an unavoidable necessity, some changes like dimming lights, using blue light filters and glasses, limiting screen time after darkness, and switching on the ‘night mode’ on your phone may help.