Halogen lamp phototoxicity.

BACKGROUND

The radiation from quartz halogen light bulbs has been reported to cause erythema in humans and skin tumors in experimental animals.

OBJECTIVE

The objective of this study was to determine the relative risk of injury to humans due to the radiation from these lamps.

METHODS

We studied a 12-volt 50-watt quartz halogen lamp. We measured its ultraviolet output spectrum and the biological toxicity of its radiation by means of its pyrimidine dimer-inducing capability.

RESULTS

At a 1-cm distance, the 254-nm light output of the lamp is 3 x 10(-7) W/cm2/nm. Solar radiation at this wavelength is undetectable on the earth's surface, i.e., less than 10(-12) W/cm2/nm. At 290 nm, the lamp output is approximately 3 x 10(-6) W/cm2/nm, 5,000 times greater than the summertime sun at 1 p.m. at sea level in Kuwait. The UVB and UVA output of the lamp is roughly similar to the solar output under these conditions. We also measured the pyrimidine dimer-forming potential of the lamps relative to the sun for the purpose of estimating the DNA toxicity of the lamps. At a 7-cm distance the lamp induces approximately 3.9 pyrimidine dimers/100,000 bp/min. This is approximately 4 times more rapid than that of the noontime summer sun in Michigan.

CONCLUSIONS

We conclude that direct radiation from these lamps can cause damage to human skin, due to their UVC and UVB output. We estimate that the relative risk to keratinocyte DNA in human skin, in vivo, from exposure to the 50-watt halogen lamp at a distance of 7 cm is between 27 and 400% of the noontime summer sun in Michigan.