Pollution caused by light an underestimated threat

cycle (circadian clock), which affects hormone production, cell regulation and other biological activities, leading to insomnia, depression, heart disease, diabetes, obesity and certain cancers, such as cancers of the breast and prostate.

Insomnia: Using back-lit tablets and smartphones at bedtime suppresses the secretion of melatonin–the hormone that regulates the sleep-wake cycle–and delays sleep and lowers alertness the next morning. Compared to reading printed material, people who read on light-emitting tablets on average slept half an hour later and had suppressed levels of melatonin, according to a study in the journal, Physiological Reports.

Depression: Chronic exposure to artificial light raises stress hormones that raise the chance of depression and lowers memory and learning, according to research done at Johns Hopkins University. The study found that blue wavelengths in bright light activate special cells (called intrinsically photosensitive retinal ganglion cells, or iprgcs) in the retina, which affects the brain’s centre for mood, memory and learning.

Breast Cancer: The International Agency for Research on Cancer has classified shift work as a probable human carcinogen. Women who live in neighbourhoods with high outdoor light at night are at a greater risk of breast cancer, according to Harvard T.H. Chan School of Public Health researchers who used data from more than 109,000 women between 1989 and 2013. The link was stronger among women who worked in night shifts and among those exposed to higher levels of light.

Many studies, including of National Health Service (NHS) employees working on a rotating night shift in the UK, have found high breast cancer risk from exposure to artificial light. Another NHS study found nurses who worked night shifts at least three times a month for 15 years or more had a raised risk of colorectal cancer.

Heart disease, obesity: Women exposed to light at night were more likely to be overweight or obese, carry fat in the abdomen, and have abnormal blood fats (cholesterol, triglycerides, among others) levels, found a study of more than 100,000 women in the UK. All these are risk factors for heart disease and diabetes.

Incandescent reading lamps: It’s not quite possible to spend your evenings in the dark, but it’s possible to reduce exposure to blue light at least at home.

Since t he light-sensing iprgcs cells in the eye are especially sensitive to blue wavelengths — found in daytime sky — avoid LCDS, LEDS, and fluorescent bulbs that favour the blue side of the spectrum to prevent your body clock from going out of whack. Instead, read in the light of circadian -friendly incandescent bulb that radiate light from heat alone that tends to be more towards the infra-red end of the spectrum.