The Effect of Artificial Light Pollution on Circadian Rhythm

Circadian rhythms are imperative biological processes that allow organisms, including animals and plants, to synchronize with Earths day-night cycle and to control numerous physiological mechanisms inside them. In mammals, the suprachiasmatic nucleus (SCN) in the hypothalamus acts as a central clock, while the peripheral clock, which is outside of the central clock, regulates the specific local functions. Within the circadian clock, the key genes like BMAL1, CLOCK, PER, and CRY coordinate with each other to form a feedback loop. The CCA1, LHY, and TOC1 genes can also form a feedback loop in plants, just like in mammals. However, due to the development of modern cities and urbanization, the widespread use of artificial light has caused severe light pollution, which disrupts the natural circadian rhythm. The source of artificial light pollution (ALP) includes streetlights, indoor and screen lights, industrial lights, etc. The ALP has already affected people worldwide, with more than 80% of the world's population experiencing it, leading to severe impacts. For instance, it can adversely affect people's physical and mental health, as well as disrupt the normal secretion of hormones such as melatonin and cortisol. Therefore, understanding the effects of ALP on circadian rhythm is important to address the growing concern of environmental impact and public health today.