Do CFLs irradiate ultraviolet rays in a harmful intensity?

Question

Someone I know complains that Fluorescent lamps are "burning" her skin. I searched for sites that confirmed this and I found:

The safety of energy-saving light bulbs is under review over concerns the low-cost green alternative may emit potentially harmful ultraviolet radiation. Health Canada launched the study in December to test compact fluorescent bulbs to see if they emit ultraviolet radiation.

Source: http://sayanythingblog.com/entry/cfl_light_bulbs_may_emit_harmful_uv_radiation/

But I want to know if there are scientific studies confirming this.

Answer 1

Some models emit ultraviolet light at an intensity which is higher than regulatory limits in the UK, if you sit too close to them. The British government's Health Protection Agency has issued this advice - here's a quote:

The Agency's view is that open (single envelope) CFLs shown in Fig. 1 should not be used where people are in close proximity - closer than 30 cm or 1 ft - to the bare light bulb for over 1 hour a day. The Agency advises that for such situations open CFLs should be replaced by the encapsulated (double envelope) type shown in Fig. 2. Alternatively, the lamp should be moved so that it is at least 30 cm or 1 ft away.

The Agency's Chief Executive Justin McCracken said, "This is precautionary advice and people should not be thinking of removing these energy saving light bulbs from their homes. We are advising people to avoid using the open light bulbs for prolonged close work until the problem is sorted out and to use encapsulated bulbs instead. In other situations where people are not likely to be very close to the bulbs for any length of time, all types of compact fluorescent light bulbs are safe to use."

Not all open (single envelope) fluorescent light bulbs have significant UVR emissions but if people are in very close proximity to some of them, the exposure to bare skin is like being outside in direct sunlight. For example, Agency scientists found that when very close (2 cm, less than 1 inch) to some open CFLs, the UVR level can be equivalent to that experienced outside in the UK on a sunny day in the summer and so some precaution is warranted. When further away (over 30 cm or 1 ft), the UVR level is much lower and less than being outside on a sunny day in winter, which is not a concern.

The question remains of whether the regulatory limits are too conservative, and I can't answer that.

Answer 2

CFL's, in fact ALL fluorescent bulbs (compact or not) naturally emit SOME ultraviolet light as a product of the process by which they produce light.

A FL is a gas discharge lamp that produces ultraviolet radiation through excitation of mercury atoms. The inside of the lamp is coated in phosphorus, that absorbs UV and emits visible light. The glass bulb itself also absorbs significant amounts of UV. In addition, if a lamp is covered with a glass lamp shade (like the ceiling lamps that provide diffuse lighting) the UV output is further decreased.

The question then becomes, how much of the UV reaches the outside world. Since the absorption cross section of the glass and the phosphorus is finite, some of UV will pass through.

The answer is - not much - at least by any natural comparable standard. Unless you are several inches from the CFL, a full working day exposure to CFL light is equivalent to several minutes - or less - of direct sunlight. Which means that a regular human being is unlikely to experience any negative effects from the ultraviolet dose he/she receives.

However, an individual with UV sensitivity, might experience negative health effects even from such a limited exposure to UV radiation.

It is also important to note that old or aging CFL's may have degradation of the phosphorus coating, CFL's that have a "clear spot" where the phosphorus has flaked off can be the source of dangerous amounts of UV and should be immediately replaced.