Almost daily people comment on my deep tan, but I’m a white Scotsman who seldom sees the sun and wouldn’t get on a sunbed if you paid me. I live in a modern flat lit by dozens of halogen bulbs. There are 36 in the living room alone. Could they be tanning my skin?
• Possibly. With 36 lamps, the room must be brighter than most, and halogen lamps do produce noticeable amounts of ultraviolet radiation. It’s UV from the sun that usually . The capsule of a halogen lamp is made of quartz to withstand high temperature and pressure, but quartz transmits ultraviolet, so in domestic lighting is added to absorb this, and a layer of glass provides additional screening. Common halogen lamps are either enclosed in an outer glass envelope, or should have a glass shield in the fitting. Your correspondent could check to see if the shield is present.
“With 36 lamps the room must be bright and halogen lamps do produce noticeable amounts of UV”
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Even so shielding is not 100 per cent effective. Assuming a bright indoor lighting level of 1000 lux, the UV radiation from normal halogen lighting is around 0.1 watts per square metre. At this rate, the , or the level of ultraviolet that causes redness of the skin, could be reached on average in a million seconds, or two continuous weeks. The permissible exposure time, to which nearly all individuals may be repeatedly exposed without adverse effects, is somewhat less.
Sensitivity to UV varies by a factor of 10, so tanning cannot be ruled out. To test for the effect, you can buy ultraviolet radiation detector stickers, but it would be simpler to apply a high factor sunscreen to a test patch of skin. It is also worth noting that antibiotics, diuretics, and coal-tar shampoos increase photosensitivity.
Slight tanning may not be a bad thing, particularly in a Scottish winter, because it boosts vitamin D levels, but if your correspondent is concerned, he could read the following paper and then eat lots of pizzas: “Tomato paste rich in lycopene protects against cutaneous photodamage in humans in vivo: a randomised controlled trial” (, vol 164, p 154).
David Craig, Edinburgh, UK
Whether the previous correspondent is correct or not, it might also be worth paying a visit to your doctor – Ed
• Your correspondent might want to find out if he has – a hereditary disease caused by the body absorbing too much iron from the diet. It is also known as bronze anaemia because of the tan it can impart and has been dubbed the “Celtic curse” because it is so common among Scots and Irish.
I too got loads of compliments on my tan until I was diagnosed with the condition and had treatment, which involves , drawing off blood. Now I’m back to my pale but healthy self. In retrospect, the lack of tan lines around my neck and wrists should have given me a clue.
Kieran Crehan, Dublin, Ireland