Artificial Light Sources and UVR

Fluorescent, neon and halogen lights emit small amounts of UVR.  These lights can be fitted with a filter or diffuser that absorbs the UVR.  Although the amount of UVR emitted by fluorescent lights is small – 8 hours of exposure is equivalent to less than 5 minutes in the sub-tropics – it is important to remember that UVR’s effect on the skin is cumulative ie the sum of the minutes is important not just the number of minutes at each time.  Cumulative UVR causes premature aging and skin cancer. 

We need to take the possible effects of fluorescent and halogen lighting seriously.  It is not only our skin and health that is affected.  UVR emitted from fluorescent and halogen lighting can fade or ‘bleach out’ the colours in fabric and textiles, and destroy valuable tapestries and manuscripts.

Halogen and xenon lamps can emit UVR.  Metal halide high intensity discharge (HID) lamps emit large amounts of UVR.  Tungsten halogen lamps with incorporated reflectors are used extensively in work, display and home lighting.  These lights emit some UVR which may be a hazard to the skin and eyes of people who remain in close proximity for long periods.  In lighting applications where the lights are close to people they should be fitted with a glass cover to block the UVR emissions

The danger and risks to our health and the environment are not just from the emitted UVR – mercury is an integral part of fluorescent and neon lighting.  It is fundamental to how they work.

How do fluorescent and neon lights work?

Mercury is an essential ingredient for most energy-efficient lamps. Fluorescent lamps, neon lights and high intensity discharge (HID) lamps are the two most common types of lamps that utilize mercury. Fluorescent lamps provide lighting for most schools, office buildings and shops and shopping centres. HID lamps, which include mercury-vapour, metal halide and high-pressure sodium lamps, are used for street lights, floodlights and industrial lighting.

A typical fluorescent light is composed of a phosphor-coated glass tube with electrodes located at either end.  The tube contains mercury, of which only a very small amount is in vapour form.  When a voltage is applied, the electrodes energize the mercury vapour, causing it to emit ultraviolet (UV) energy rather than visible light energy.  Although the process of producing light from the mercury atoms is fairly efficient, it produces UV not visible light.  When the ultraviolet light strikes the powder, it produces excitations of the electrons of the phosphor which then produce visible light by a process called fluorescence. 

Without the mercury vapour to produce UV energy, there would be no light.  A one metre fluorescent lamp has an average rated life of at least 20,000 hours.  To achieve this long life, lamps must contain a specific quantity of mercury.  The amount of mercury required is very small, typically measured in milligrams, and varies by lamp type, date of manufacture, manufacturing plant and manufacturer.

Fluorescent lighting produces a highly energy efficient lighting, as long as we do not use a life cycle analysis.  Unfortunately, the mercury contained in fluorescent lights is a toxic pollutant that persist in the environment and harms human health.

Mercury causes damage to living things.  It damages the human brain, spinal cord, kidneys and liver.  It is especially dangerous during foetal development and to small children.  Any products containing mercury must be recycled to keep this dangerous element out of our environment.

When a fluorescent light or tube is broken or placed in a landfill or incinerator, mercury is released into the environment.  The amount of mercury contained in just 25 standard fluorescent lamps can pollute a 8 hectare (20 acre) lake, making the fish in the lake unsafe for human consumption.

Approximately 80 percent of all fluorescent lights and tubes are used by commercial buildings.  Many million of these are discarded each year, making these lights one of the largest sources of mercury in the solid waste stream.