On December 13, 2013, the European Commission (EC) Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) released its preliminary opinion on “Nanosilver: safety, health and environmental effects and role in antimicrobial resistance.” The opinion is intended to assess whether the use of nanosilver, in particular in medical care and in consumer products, could result in additional risks compared to more traditional uses of silver, and whether the use of nanosilver to control bacterial growth could result in resistance of micro-organisms. SCENHR states that it “concluded that the widespread (and increasing) use of silver containing products implicates that both consumers and the environment are exposed to new sources of silver.” Human exposure is direct, through food, hand-to-mouth contact, and skin, and may be life long. Silver nanoparticles “may be a particularly effective delivery system for silver to organisms in soil, water and sediment and may act as sources of ionic silver over extended periods of time.” SCENIHR thus cannot rule out “additional effects caused by widespread and long term use” of nanosilver. Regarding the hazard associated with the dissemination of the resistance mechanism following the use of nanosilver, SCENIHR notes that there is no documentation available, “representing a serious gap of knowledge.” According to SCENIHR, “[s]ince other nanoparticles have been shown to substantially increase the horizontal gene transfer between bacteria — which is extremely relevant for developing resistance — the potential of [nanosilver] to induce similar effects should be given particular attention.” SCENIHR states that more data are needed to understand better the bacterial response to ionic silver and nanosilver exposure. SCENIHR could not determine whether resistant microorganisms will increase and spread in view of a more widespread use of nanosilver because the mechanisms resulting in nanosilver resistance are not well understood. Comments on the preliminary opinion are due February 2, 2014.