Human health risks of engineered nanomaterials: Critical knowledge gaps in nanomaterials risk assessment
There are currently hundreds of available consumer products that contain nanoscale materials. Human exposure is, therefore, likely to occur in occupational and environmental settings. Mounting evidence suggests that some nanomaterials exert toxicity in cultured cells or following in vivo exposures, but this is dependent on the physicochemical characteristics of the materials and the dose. This Working Group report summarizes the discussions of an expert scientific panel regarding the gaps in knowledge that impede effective human health risk assessment for nanomaterials, particularly those that are suspended in a gas or liquid and, thus, deposit on skin or in the respiratory tract. In addition to extensive descriptions of material properties, the Group identified as critical research areas: external and internal dose characterization, mechanisms of response, identification of sensitive subpopulations, and the development of screening strategies and technology to support these investigations. Important concepts in defining health risk are reviewed, as are the specific kinds of studies that will quickly reduce the uncertainties in the risk assessment process.