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White Light Suppresses Melatonin More

HAIFA, Israel, Oct. 7, 2011 — A new international study reveals that the light from white LED bulbs suppresses melatonin five times more than exposure to the light of the more commonly used high-pressure sodium (HPS) bulbs, which give off an orange-yellow light.

Melatonin is a compound that adjusts our biological clock and is known for its antioxidant and anti-cancerous properties.


Both metal halide bulbs (shown here) and LEDs that emit white light have been shown to suppress the body's cancer-fighting compounds more than high-pressure sodium bulbs, according to a new study. (Images: Lynn Savage/Photonics Media)

The fact that white artificial light, which is actually blue light on the spectrum, emitted at wavelengths of between 440 and 500 nm, suppresses the production of melatonin in the brain's pineal gland is already known. Also known is the fact that suppressing the production of melatonin causes behavior disruptions and health problems.

“Just as there are regulations and standards for ‘classic’ pollutants, there should also be regulations and rules for pollution stemming from artificial light at night," said Abraham Haim, head of the Center for Interdisciplinary Chronobiological Research at the University of Haifa.

In this study, conducted by astronomers, physicists and biologists from ISTIL (Light Pollution Science and Technology Institute) in Italy, the National Geophysical Data Center in Boulder, Colo., and the University of Haifa, researchers for the first time examined the differences in melatonin suppression in various types of lightbulbs, primarily those used for outdoor illumination, such as streetlights, road lighting, mall lighting and the like.

In the first, analytical part of the study, the researchers, relying on various data, calculated the wavelength and energy output of bulbs that are generally used for outdoor lighting. Next, they compared that information with existing research regarding melatonin suppression to determine the melatonin suppression level of each bulb type.

Taking into account the necessity for artificial lighting in cities as well as the importance of energy-saving bulbs, the research team took as a reference point the level of melatonin suppression by an HPS bulb (often used for street and road lighting) and compared the data from the other bulbs to that one.

From this comparison, it emerged that the metal halide bulb, which gives off a white light and is used for stadium lighting, among other uses, suppresses melatonin at a rate more than three times greater than the HPS bulb, while the LED bulb, which also gives off a white light, suppresses melatonin at a rate more than five times higher than the HPS bulb.

The researchers said that the current migration from the now widely used sodium lamps to white lamps will increase melatonin suppression in humans and animals.

“Most Italian regions have legislations to lower the impact of light pollution, but they still lack a regulation on the spectrum emitted by lamps. Unless legislation is updated soon, with the current trend toward sources as white LEDs, which emit a huge amount of blue light, we will enter a period of elevated negative effects of light at night on human health and environment,” said Dr. Fabio Falchi of ISTIL. “Lamp manufacturers cannot claim that they don't know about the consequences of artificial light at night.”

“As a first step in Israel, for example, the Standards Institution of Israel should obligate bulb importers to state clearly on their packaging what wavelengths are produced by each bulb,” said Haim. “If wavelength indeed influences melatonin production, this is information that needs to be brought to the public's attention, so consumers can decide whether to buy this lighting or not.”

The study was published in the Journal of Environmental Management.

For more information, visit: www.haifa.ac.il/index_eng  


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