file] 2012, 424, 88-96 (Eng) Over the last 20 years hair has moved from being a highly questionable biological matrix to mainstream and acceptable biomarker in forensic sciences where it is primarily used to determine past and present exposure to illicit drugs. In contrast, the use of hair to assess exposure to pesticides and persistent environmental pollutants is still not common. The applicability of this matrix to assess an individual’s body burden of chemicals such as polybrominated di-Et ethers (PBDEs) can provide critical insight into current, but also to past exposure levels, which is not possible with more conventional matrixes such as blood and urine. Furthermore, as PBDEs cross the placenta and since the hair the foetus is born with begins to grow during the third trimester, this matrix can be used to assess in utero exposure. These features of hair may therefore be used to determine the potential roles of chemicals such as PBDEs in mediating physiological or anatomical abnormalities in infants, children or adults.