by Dr. Samuel Epstein


Silica: Fumed silica, prepared by heating crystalline silica with hydrochloric acid, is used as a filler in the shell manufacturing process. Through this process, any residual crystalline silica can be become embedded in the shell and subsequently liberated by degradation. The FDA's internal reports refer to the Agency's efforts to obtain corroborativeinformation from the manufacturers, who reportedly have denied the presence of freesilica in implants (Dillon,1994). Such claims, however, have been challenged by arecent publication based on in vivo rat models, which demonstrated that silicone isneither chemically nor metabolically inert. Silicone gel was shown to degrade to freesilicon dioxide, and relatively high silica levels-up to 36mg/g-were found in the implantcapsule. These findings recently have been further confirmed through in vitro studies onbloon and in vivo liver studies of human volunteers with breast implants. Using NMR,these studies indicated evidence of transformation of silicone to silicon dioxide or silica. Whether the silica is in the amorphous or crystalline form, however, has not yet beendetermined. In addition to a wide range of other contaminants, the presence of free silica in implants is well recognized by FDA. " It should be noted that silicone polymers areknown to contain macromolecules by peroxide crosslinkages, additives,catalysts(platinum) and fillers (solid or fumed silica). Chemical intermediates fromwhich silicones have been synthesized were also found to be corrosive and highly irritating to animals and humans. In addition, it has been pointed out that silicone gel, being lipophilic, selectively binds progesterone and other lipids. The affinity of liquid silicone for progesterone is 50 times more than for estrogens. Possible uptake of highconcentrations of hormones at the implant site was postulated to be the cause of increase cancer incidences found in animal studies."

Source: Implants Pose Poorly Recognized Risks of Breast Cancer By: Samuel Epstein Journal: International Journal of Occupational Medicine and ToxicologyVol.4,No.3,1995