Response to the letter to the editor by Andrew Millard

This paper presents our reply to two questions posed by Dr. Millard concerning our paper Martínez-García et al. [Martínez- García MJ, Moreno JM, Moreno-Clavel JM, Vergara N, García-Sánchez A, Guillamón A, Portí M, Moreno-Grau S. Heavy metals in human bones in different historical epochs. Sci Total Environ 2005;348:51–72], namely, whether diagenetic changes operating in human bones after burial and consideration of the physiological plausibility of the metal concentrations measured in such bones could invalidate the results presented in the aforementioned paper. In our reply, we show that diagenetic effects are not meaningful in our study and that the mathematical approach used by Millard to derive circulating blood concentration from bone levels is based on the incorrect manipulation of a statistical regression analysis and therefore is not valid. After exhaustively reviewing the two phenomena involved in Dr. Millardʹs questions as well as other concerns raised in his letter to the editor, we deem the three conclusions presented in Martínez-García et al. [Martínez-García MJ, Moreno JM, Moreno-Clavel J, Vergara N, García-Sánchez A, Guillamón A, Portí M, Moreno-Grau S. Heavy metals in human bones in different historical epochs. Sci Total Environ 2005;348:51–72] to be entirely appropriate.