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There is something instinctive about our love of sunlight. Most people would say that they feel better after being outdoors on a bright, sunny day without knowing why. As our understanding of UV light properties and effects on organisms has developed over the decades, we better understand its effect on humans and we’ve learned to harness the power of the sun to improve human health.

Early understanding of the sun’s health properties

UV light has been used as a therapeutic agent throughout history. Originally known in ancient Greece as heliotherapy (after the Greek sun god Helios), it had been observed that sunlight prevented the growth of harmful substances in water and a similar beneficial health effect seemed to arise in people who received exposure to the sun’s rays. Other civilizations such as Rome and Egypt also recognised these benefits and practised similar therapies. Even today, research continues into the disinfection properties of natural sunlight for disease prevention in developing countries.

Discovery of ultraviolet light and its properties

The notion of “invisible light” emitted by the sun was discovered by accident in 1800 by astronomer William Herschel, with German physicist Johann Ritter a year later observing some of the chemical reactions these wavelengths effect, leading to his naming the phenomena “oxidising rays”, becoming known much later as ultraviolet radiation.


William Herschel (left) and Johann Ritter (right)

By 1877 Downes and Blunt had discovered the germicidal properties of sunlight, particularly at the violet end of the visible spectrum. As the 19th century drew to a close, further work demonstrated that ultraviolet light, invisible to human eyes, was even more effective.

This led on to the development of the first mercury gas discharge lamps as artificial UV light sources as early as 1901, with research continuing into the 20th century on both germicidal disinfection and medical treatment.

UV light as a medical treatment

In 1903 Niels Finsen of Denmark received the Nobel Prize for Medicine for his use of an ultraviolet lamp to successfully treat the disfiguring lesions caused by tuberculosis of the skin. Before long, UV was used widely in the medical world for the treatment of a variety of ailments.

Finsen lamp

Treatment using a Finsen lamp, London, 1925 (Wellcome Library)

Eco-UV Partner Hanovia, now one of the world’s largest manufacturers of UV industrial water treatment systems, started out in the 1920s as a medical UV lamp supplier to practitioners of quartz light therapy, later actinotherapy or phototherapy, as ultraviolet light treatment became known.

Actinotherapy grew in popularity in the early 20th century and peaked in the mid-century, in particular applied to children suffering from vitamin deficiency and as so-called “sun ray therapy” for inner city children suffering the effects of living in crowded and polluted conditions where exposure to natural sunlight was scarce.

Rickets treatment

Treatment for rickets, 1925

There were major developments in understanding the effects of UV light throughout the 1950s and by 1960, the effect of ultraviolet radiation on DNA was established - and with it a better understanding of the health risks associated with UV exposure. That, combined with the advent of antibiotics, led to a sharp decline in phototherapy as a medical treatment.

The medicinal use of UV light remains an important and effective medical treatment to this day for certain conditions, albeit a highly specialised area requiring careful supervision during treatment.

UV germicidal treatment and water disinfection

In 1910, seven years after Finsen won his Nobel Prize, the first UV application of drinking water disinfection was active in Marseilles, France. Despite substantial developments in UV disinfection occurring throughout the first half of the 20th century, the low cost of chlorine and operational problems with early UV disinfection equipment limited its growth as a drinking water technology. The first reliable applications of UV light for disinfecting drinking water occurred in Switzerland and Austria in 1955 and then grew rapidly, particularly after harmful chlorinated disinfection by-products were discovered.

Hanovia launched its first water disinfection lamps in 1939 (low pressure), following up with high pressure variants in 1942. By 1949, despite chlorination being the dominant drinking water disinfection method in the UK, Hanovia was the market leading supplier of UV water and process liquid disinfection to industry across Europe, mainly in the food, pharmaceutical and beverage sectors – a position and expertise it has never relinquished.

Chamber internal

Unleashing the full power of UV

UV water disinfection is now widely used around the world for municipal drinking water supplies, industrial processes and wastewater treatment, and the market is growing rapidly – between 10 and 20% annually in recent years, according to the IUVA website. The UV light source can be completely contained and the risk of exposure is almost zero. It also possible now to target only the most effective wavelengths of UV light at very high intensities to deactivate specific bacteria and viruses, rendering water safe to use in a clean, sustainable process.

The Eco-UV project continues the long history of innovation in using ultraviolet light for human health purposes. It will provide more clean water and keep more people healthier, without causing damage to the environment. No wonder we love the sunshine!

Hanovia logo old

Further Reading

The Irish man who uses the sun to make drinking water safer, The Irish Times, 18th September 2016.

Ultraviolet Disinfection Guidance Manual for the Final Long Term 2 Enhanced Surface Water Treatment Rule, United States Environmental Protection Agency Report EPA 815-R-06-007, November 2006.

International Ultraviolet Association,