Answer to bad hair days in the pipeline The copper comes in from the tap water and the hair acts like a sponge picking it up over time. Colouring hair can create free radicals that damage the protein in the hair and the copper can catalyse that reaction. In the same way, UV exposure from going out in the sun can do the same thing over a longer period of time. Physical processes like brushing, blow drying and washing, hair is less able to stand up to those and it will break down faster and lead to split ends, lack of shine and make it harder to manage. Dr Marsh and her colleagues analysed hair from 450 women from around the world and found that they had varying levels of copper in their hair. On average most had levels of around 20-200 atoms of copper for every million molecules in their hair. Some, however, had levels that were more than 500 parts per million. Low levels of copper in drinking water are thought to occur naturally while purifying processes used by water companies can add more. Most copper, however, comes from traditional copper pipes used in British houses. Even in homes with plastic piping, hot water tanks can be made from copper. As a single strand of hair can grow for up to three years before falling out, the low levels of the metal in the water can build up in the outer layers of the hair, the researchers found. Once there it increases the formation of reactive molecules that break down the outer sheath of the hair, known as the cuticle, and the hair's cortex. This strips hair strands of their shine and leaves them weaker than normal, meaning they are more prone to breaking when brushing or to damage from blow drying. However, the researchers, whose findings are published in the International Journal of Cosmetic Science, found that treating hair with chemicals more commonly used in washing powder, known as chelants, they could reduce the action of the copper. Dr Jeni Thomas, principal scientist at Pantene, said they were now attempting to incorporate chelants into hair dyes to reduce the damage caused by copper and hoped to produce a shampoo in the future too. She said: "Everyone seems to have copper in their hair, but the levels seem to vary a great deal. You often can't see the effects under the microscope, which is why we believe copper has been largely missed as a source of damage. At the moment we are focusing on tackling this in hair colour formulations but we exploring how that can be used in everyday hair care.