Impacts of Light Pollution on Human Health

Humans are diurnal - we evolved to be active during the day and sleep at night. Thanks to electric lighting, we are able to work and do recreational activities even after darkness has fallen. This means that we are often exposed to artificial light at night, which scientists agree can be harmful to our health.

The circadian rhythm

The circadian rhythm regulates physiological, biological, and mental behaviours, including the sleep-wake cycle, and is the foundation of overall health [1] [2]. It is synchronized by the natural cycle of light and dark [3]. We alter that light:dark cycle by lighting up our houses, streets, and cities after the sun sets. This alteration of the natural light:dark cycle disrupts the natural circadian rhythm.

Disruption of the circadian rhythm is linked to a number of health concerns in humans, including cancer, diabetes, weight gain, reduced immune system function, cardiovascular risks, depression, and other mood disorders [4].

Sleep

Melatonin, the hormone our bodies release to produce feelings of sleepiness, is only produced in response to growing darkness. Exposure to artificial light at night may confuse our bodies into thinking it is still daylight, which can suppress melatonin release and negatively affect sleep time and quality [5]. Blue light has the same effect, which is why many experts recommend not looking at cell phones, computers, and other bright screens before bed.

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For scientific articles that explore how artificial light at night affects human health, visit our Public Google Drive. 

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[1] Blume, C., Garbazza, C. & Spitschan, M. Effects of light on human circadian rhythms, sleep and mood. Somnologie 2019: 23, 147–156. https://doi.org/10.1007/s11818-019-00215-x

[2] Kantermann T. Circadian Biology: Sleep-styles Shaped by Light-styles. Curr Biol. 2013: 23(16), R689-90. doi: 10.1016/j.cub.2013.06.065. PMID: 23968925.

[3] Vetter, C. Circadian disruption: What do we actually mean? Eur J Neurosci. 2020: 51(1), 531-550. doi: 10.1111/ejn.14255. Epub 2018 Dec 5. PMID: 30402904; PMCID: PMC6504624.

[4] Chepesiuk R. Missing the dark: health effects of light pollution. Environ Health Perspect. 2009: 117(1):A20-A27. doi:10.1289/ehp.117-a20

[5] Yang, M., Ma, N., Zhu, Y., Su, Y.C., Chen, Q., Hsiao, F.C., Ji, Y., Yang, C.M., Zhou, G.. The Acute Effects of Intermittent Light Exposure in the Evening on Alertness and Subsequent Sleep Architecture. Int J Environ Res Public Health. 2018: 15(3), 524. doi: 10.3390/ijerph15030524. PMID: 29543731; PMCID: PMC5877069.