The Metalloid Elements, Selenium and Silicon
Selenium and silicon are non-metals with established roles in human nutrition. Both elements are widely disseminated in the environment. The carcinogenicity of selenium sulphide, as suggested from limited experimental animal studies, is not substantiated. However, chronic inhalation of silica dust as fine particles of respirable dimension is an undisputed pulmonary carcinogen in humans and animals. Controversies regarding the use of silicone gels in mammoplasty are reviewed, but whilst tumours are reported at sites of implantation, population studies have established that biodegradable silicones are not a primary cause of breast cancer. Talc (magnesium silicate) has not been conclusively proven to be carcinogenic in occupational exposure, and the risk of ovarian cancer arising through use of talcum powder for hygiene purposes is not proven. Talc is not biodegradable and undissolved particles are demonstrated in tissue by their birefringence under polarised light. The use of silicones in wound care and skin therapies is more beneficial to patients than a source of health risk or toxicological effect.