Analysis of silicon in human tissues with special reference to silicone breast implants

The increase, in the last two decades, in the application of silicones (pol ysiloxanes) and inorganic silicon compounds in medicine and the food indust ry, has exposed the human body to extensive contacts with these substances. Most silicone breast implants contain a gel consisting of a crosslinked si licone elastomer swollen by silicone oil (PDMS). Diffusion of PDMS through the silicone elastomer envelope and rupture of the envelope with release of the gel contents both occur clinically. The amount and distribution of sil icone compounds in Various tissues are key issues in the assessment of heal th problems connected with silicone implants. We have measured by GFAAS the Si content of tissues from normal and implant patients and the organic solvent extractable Si levels (assumed to be sili cone), using careful control of sample collection and preparation. Whole bl ood levels were: implant patients mean 38.8 (SD 25.6) (mu g/kg), controls m ean 24.2 (SD 26.7) (mu g/kg) in one study and subsequently 103.8 (SD 112.1) and 74.3 (SD 86.5) (mu g/kg) in another study. Capsular tissue levels were : gel implants 25047 (SD 39313) (mg/kg of dry tissue), saline implants 20.0 (SD 27.3) (mg/kg of dry tissue) and controls 0.24 (SD 0.39) (mg/kg of dry tissue). Breast milk levels were: implant patients mean 58.7 (SD 33.8) (mu g/kg), controls mean 51.1 (SD 31.0) (mu g/kg); infant formula mean was 4.40 (mg/kg). Various precautions were undertaken to avoid Si contamination in this work, the most important being a) the use of a Class 100 laboratory fo r sample preparation and b) application of strict and elaborate washing pro cedure for specimen collection tools and laboratory plasticware. This data demonstrated that to properly interpret the importance of these n umbers for human health, a larger study of "normal" levels of Si in human t issues should be undertaken and factors such as diet, water, race and geogr aphical location should be considered.