One of the hallmarks of scientific knowledge is the ability of researchers to replicate results. This has eluded scientists studying the health effects of exposure to nanomaterials for a variety of reasons. Among the factors are: the unavailability of standardized engineered nanomaterials for testing; differences among the many manufacturers of nanomaterials; lack of standard protocols; and variations in toxicity among particles due to the way the particles behave in certain situations.
To attempt to resolve these problems, dozens of researchers from universities and NIOSH participated in what has been called the NanGo Consortium to conduct health studies on engineered nanomaterials using the same materials and developing standard protocols. The program was developed by the National Institute of Environmental Health Sciences (NIEHS).
The inter-laboratory, multi-investigator Consortium defined some of the challenges it faced as follows:
“In addition to dose, there are multiple factors that influence the toxicity of ENMs, including surface characteristics, charge, and shape. Size alone is a major determinant as many bulk materials that are relatively inert become toxic when produced at the nanoscale. . . . Determination of which ENMs will present the greatest potential threat to human health depends on relative toxicity, and on the potential for exposure.” (pp. 5-6)
The Consortium conducted two broad sets of studies. The first involved rats and mice exposed to carbon nanotubes and titanium dioxide, and measured pulmonary inflammation. The Consortium concluded: “The results presented and discussed herein demonstrate that a standard protocol can be used across multiple laboratories to yield similar results in the pulmonary inflammatory response.” (pp. 6-7) The researchers are optimistic that with this start, there will be opportunities to determine the impact that exposure to nanomaterials may have on human at the preventive stage.
The second study examined the effects of carbon nanotubes, titanium dioxide, and zinc oxide in vitro in laboratory container studies. The Consortium noted: “A significant finding of this study was that the development of harmonized in vitro assay protocols made it possible to achieve reproducible results among different laboratories.” (p. 16) This study, the Consortium concluded, “provides new information on the relative in vitro bioactivity of a large group of diverse ENM that can be used to inform future strategies for in vitro testing and predicting in vivo outcomes.” (p. 6)
These studies move researchers in the direction of being able to replicate results and ultimately draw reliable conclusions about the potential health hazards of exposure to nanomaterials, leading to effective regulation.
The NIEHS NanoGo Consortium reports are available at
http://ehp.niehs.nih.gov/wp-content/uploads/121/4/ehp.1205693.pdf
http://ehp.niehs.nih.gov/wp-content/uploads/121/4/ehp.1306561.pdf
