Heavy metals, principally mercury and silver, are now rarely used as disinfectants. Mercury is an environmental hazard, and some pathogenic bacteria have developed plasmid-mediated resistance to mercurials. Hypersensitivity to thimerosal is common, possiblyin up to 40% of the population. These compounds are absorbed from solution by rubber and plastic closures. Nevertheless, thimerosal 0.001–0.004% is still used safely as a preservative ofvaccines, antitoxins, and immune sera. Although a causative link to autism has never been established, thimerosal-free vaccines are available for use in children and pregnant woman.
Inorganic silver salts are strongly bactericidal. Silver nitrate, 1:1000, has been most commonly used, particularly as a preventive for gonococcal ophthalmitis in newborns. Antibiotic ointments have replaced silver nitrate for this indication.Silversulfadiazine slowly releases silver and is used to suppress bacterialgrowth in burn wounds.