By Reginald DaveyReviewed by Emily Henderson, B.Sc.
Since the prehistoric era, mankind has used a variety of light sources. The earliest light source utilized was fire, but over the past two centuries electricity has been used and today, electric lighting is everywhere. However, there are concerns that artificial light can affect the health of humans. This article will discuss the subject.
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How Light Affects Living Organisms
All light sources emit both visible light and invisible radiation. The types of radiation include ultraviolet and infrared, and these can be further subdivided into narrower bands corresponding to their wavelength. The sun is the main source of harmful radiation, but the majority is blocked by the earth’s atmosphere. The color of visible light also depends upon its wavelength, from violet (short wavelength) to red (long wavelength.)
The harmful effect of light depends on a few factors. These include which radiation it is, its wavelength, and the cell type. If the light reaches chromophores, which are absorbing molecules present in cells, visible and UV light can induce chemical reactions within those cells. Chromophores are particularly abundant in skin and eye cells. Infrared light, when it illuminates matter, can cause it to heat up. The depth of penetration depends upon the wavelength of the radiation.
Defense Mechanisms Against Light Radiation
The body has evolved several defense mechanisms against bright or hot light. These are both biological and behavioral, including pain responses, blinking, pupil constriction, and a natural aversion to bright lights. Molecules such as antioxidants and naturally occurring pigments in the skin slow down adverse chemical reactions by destroying excessive levels of harmful molecules caused by penetrating radiation.
However, even with these defenses, the body can still be harmed by exposure to artificial light. Too much radiation from a strong artificial light source, for example, can cause the formation of toxic levels of harmful chemicals. For this reason, safety protocols exist governing exposure levels and the strength of commercially available lighting.
Potential Health Risks Linked to Artificial Lighting
Short-term exposure to UV light generally carries a minimal risk, and most commercially available lighting (for example, household and commercial lights) are not strong enough to cause damage in the long term. One of the most common risks linked to long-term UV exposure is the development of squamous cell carcinomas, but the risk posed by most artificial lighting is still low.
Whilst sunlight is the main disease trigger in patients with light sensitivity, artificial light can exacerbate disease in extremely sensitive individuals. In patients with conditions such as chronic actinic dermatitis, the UV or blue component of artificial light can aggravate the associated skin lesions. Also, in sufferers of lupus erythematosus, it can worsen the disease. Patients are advised to avoid artificial lighting with these components.
It is not just skin conditions that can be aggravated by artificial light. Certain wavelengths can worsen retinal dystrophy and it is for this reason that patients are advised to use protective eyewear to filter them out. Effects of artificial light on patients with light-sensitive eye conditions vary between individuals and have a genetic element.
Further Risks
Beyond the direct risks of cancer and the effect upon light-sensitive individuals, there are other risks to human health. The use of artificial light at night-time has been linked to increased risk of sleep disorders, obesity, depression, metabolic disorders, and even breast cancer.
Humans have evolved to develop a circadian rhythm of being awake during the day and asleep at night. The widespread use of artificial lighting in streetlamps, offices, stores, homes, and a multitude of other locations worldwide has interrupted this natural rhythm. In fact, it can be said that almost none of us experience a truly dark night.
The reason for this is the hormone melatonin. This hormone is produced by the body in response to the circadian rhythm and its production is suppressed by too much light at night-time. Melatonin has many beneficial health effects, including antioxidant properties, lowering cholesterol, aiding sleep, and boosting the immune system. It also aids the healthy function of the adrenal gland, testes, ovaries, pancreas, and thyroid gland.
Research suggests that the main culprit is blue light. This can be found in fluorescent lighting and common electronic devices such as laptops, computer monitors, smartphones, and televisions. However, simple solutions such as turning off devices rather than leaving them on standby, reducing screentime at night, wearing a sleep mask, and choosing lamps that do not emit blue light can mitigate these effects.
In Conclusion
There is a growing body of evidence linking artificial light to several health conditions, both physical and mental. More data are needed on long-term exposure to outdoor lighting and the blue light in use in indoor lights to be able to mitigate risk effectively. This is especially pertinent as new forms of artificial lighting are developed for widespread domestic and commercial use.
References:
- European Commission (website) Health Effects of Artificial Light [Accessed online 10th July 2021] https://ec.europa.eu/health/scientific_committees/opinions_layman/artificial-light/en/index.htm
- International Dark Sky Foundation (website) Light Pollution Human Health [Accessed online 10th July 2021] https://www.darksky.org/light-pollution/human-health/
- Harvard University Department of Sleep Medicine (website) The Drive to Sleep and Our Internal Clock [Accessed online 10th July 2021] http://healthysleep.med.harvard.edu/healthy/science/how/internal-clock
