Whites are no longer whiter

Many laundry detergents which claim to "whiten" fabrics actually do nothing of the sort.

Ageing white clothes take on a yellow tinge and some detergents combat this by leaving a chemical residue nestled in the fibres to reflect extra blue light. The yellow is there but it's less visible as it is offset by this blue shine.

But LED (light-emitting diode) lighting could upset this trick. The bulbs present a problem for detergent companies as the fluorescence cannot happen under the light they give out.

Fluorescents reflect ultraviolet light, but LED bulbs tend not to give out anything in that part of the spectrum so there is nothing to "excite" the particles.

LED bulbs offer a life span many times that of traditional bulbs and their market could rise 12-fold over the next decade. Las Vegas recently converted more than 40000 street lights to LEDs .