Adverse health effects following exposure to engineered nanomaterials

Advances in nanotechnology have enabled fabrication of nanomaterials with defined structures that areincreasingly being used for commercial purposes. Unlike chemical toxins, nanomaterials have unique interactions with macromolecules and cells based on their molecular size and interfacial physiochemistry. Adverse human health impacts due to occupational and environmental exposures to engineered nanomaterials (ENMs) are therefore of concern. Although the impact of ENMs on biological systems is still not clearly understood, strong evidence suggests that nanomaterials are present in human fluids and tissues. Effective and feasible hazard assessment of ENMs is urgently needed to guide regulation and policy-making and support the development of benign next generation ENMs. Beyond the physical parameters of the NMs themselves, the surrounding biological system has been shown to influence NM behavior, the nano-cellular interface, and subsequent biological responses. It has recently been established that ENMs, upon entry into a physiological environment, exhibit a tendency of physical adsorption with proteins, peptides, lipids and amino acids to render a "biocorona" that may influence the bioavailability and distribution of ENMs within the host system, at the cellular, tissue and whole organism level. Consequently, research on the health and safety implications of ENMs must include assessments of how the biocorona may impact toxicity and lead to a new 'biological' identity of the ENM. Although ongoing research suggests that almost every organ and organ system may be affected by ENMs, in this review we will focus on the main pathogenetic mechanisms and on key organ and organ systems such as the lung, the skin and the gastro-intestinal tract; we will also highlight several challenges associated with a comprehensive evaluation of their toxicity, including the vast and diverse array of ENM products, dependence on physicochemical characteristics and exposure matrices, and difficulties in quantifying dosimetry and dose-response. Possible attempts to overcome these challenges are also discussed.