Each centimetre of hair analysed provides information on pesticide exposure over a period of one month.
Up to 6 centimetres of hair can be analysed. Beyond 6 centimetres (i.e. 6 months) the interpretation of the results becomes more difficult due to the natural alteration of the hair and the possible degradation of its structure by hair and cosmetic treatments.
Blood and urine tests provide information on recent exposure dating back no more than a few days before the sample was taken (up to 24 hours for blood and up to 72 hours for urine). For continuous monitoring, it is necessary to take more samples.
Hair analysis is therefore more economical and better suited to the assessment of chronic exposure than blood or urine analysis. Not to mention the problems of collecting, transporting and storing blood and urine samples.