Napoleon’s favorite color was green – that’s why his wallpapers had this color. This probably became his undoing: he died of chronic poisoning with arsenic, a component of the green dyes used at the time. Or maybe he was poisoned deliberately. How do you come to such assumptions, centuries after his death? His hair showed the scientists the solution to the riddle.
Hair is a horny structure that grows from the skin. Its lower part, the hair root, participates in the metabolic process, then keratinizes and is pushed outward, an average of one centimeter per month. Hairs are not really necessary – their tasks of heat insulation, friction reduction and participation in the sense of touch can also be well taken over by other structures. Psychologically, they have a higher value – as part of individual expression, they are shaped and blow-dried, cut and lengthened, straightened, curled and colored.
Searching for traces on the head
Especially in legal and environmental medicine, hair is used to detect poisons, drugs and trace elements. They are exceptionally well suited for this purpose – such substances and their degradation products readily accumulate in the hair structure during keratinization and remain detectable there even after a long time. If the liver has broken down the excessively consumed alcohol after a few hours to such an extent that the driver’s license is not taken away even during a breathalyzer test, hair reveals even after weeks whether the hair wearer smokes.
Advantages and disadvantages of hair analysis
Advantage is therefore that the hair is not like blood or urine only a snapshot of the current body events, but reflect chronic stress or poisoning over a longer period. The disadvantage is that not all substances can be detected equally well and that chemical treatment of the hair such as dyeing or frequent swimming in chlorinated water can render the results of the analysis unusable. Furthermore, not only foreign substances ingested through eating, inhaling or injecting can be detected in hair, but also direct contact, e.g. with dusts, can lead to deposits. Distinguishing between these modes of uptake is difficult for certain substances.
Performance and evaluation of hair analyses
Approximately 500 mg of hair (about 2 tablespoons full) or 2 tufts of hair, each 5 mm in diameter, are required for the sample. The length should not be less than 2-3 cm. The hair is cut directly at the scalp. It is best to coordinate the details of the collection with the respective laboratory. Cosmetically treated hair (dyeing, tinting, perming, etc.) cannot be used. In order to be able to assess the results correctly, other factors should ideally also be taken into account. These include influencing factors such as gender, age, season, type of housing, drinking water content, smoking behavior, dust exposure at the workplace, metal precipitation indoors or lead in the outdoor air, and hobby activities. In addition, documentation of hair color, hair type, information on hair washing and shampoo used, hair treatment, and swimming habits is also relevant.
