What we know about engineered nanoparticles' health and environmental safety
(Nanowerk Spotlight) In 2008, the Joint Research Centre, Institute for Health and Consumer Protection of the European Commission funded the project Engineered Nanoparticles: Review of Health and Environmental Safety (ENRHES), an international collaborative review involving researchers from Edinburgh Napier University (ENU), the Institute of Occupational Medicine (IOM), the Technical University of Denmark (DTU), JRC's Institute for Health and Consumer Protection, and the Institute of Nanotechnology (IoN). Last month, the ENRHES project released its final report (available as a free download).
Before we take a look at the report's findings, it's quite remarkable that the authors feel compelled to start their introduction section with this sentence: "Nanotechnology is a sector of the material manufacturing industry that has already created a multibillion $US market, and is widely expected to grow to 1 trillion $US by 2015." Firstly, a lot of people would argue with the narrow definition of nanotechnology as being a sector of the material manufacturing industry. Secondly, it appears that still no publicly funded report can afford to omit the meaningless and nonsensical reference to a 'trillion dollar industry by 2015'. It really is astonishing how this claim gets regurgitated over and over again – even by serious scientists – without getting scrutinized (read "Debunking the trillion dollar nanotechnology market size hype"). It would be interesting to know if scientific authors, who otherwise operate in a fact-based world, just accept a number picked out of thin air by some consultants because it helps impress their funders; or if they deliberately use what they know is a fishy number because the politicians and bureaucrats who control the purses are easily fooled by sensational claims like these and keep the funding coming.
Thankfully, the rest of the report stands on solid ground.
The overall aim of the ENRHES project was to perform a comprehensive and critical scientific review of the health and environmental safety of four classes of nanomaterials: fullerenes, carbon nanotubes, metals and metal oxides. The review considers sources, pathways of exposure, the health and environmental outcomes of concern, illustrating the state-of-the-art and identifying knowledge gaps in the field, in order to coalesce the evidence which has emerged to date and inform regulators of the potential risks of engineered nanoparticles in these specific classes.
The specific objectives of the ENRHES project were to review information on:
production, use and exposure to the target engineered nanomaterials;
persistence, bioaccumulation, toxicity and interactions of the engineered nanoparticles in living and environmental systems;
differences in toxicity posed by variations in physico-chemical characteristics.
The final objective of the project was to perform a coherent evaluation of the feasibility of conducting a regulatory risk assessment for each material type and perform basic risk assessments to the extent possible based on the information presented within the review.
Overall, the report paints a picture of the current state of knowledge concerning exposure to nanoparticles and ongoing work in the area. The author team has developed prioritized recommendations and set them in the context of informing policy makers in the development of methods to address exposure as it relates to the potential hazards.
They conclude that their findings "strongly supports the further development of thorough characterization (including proper considerations of agglomeration/aggregation) of the nanoparticles in exposure media when conducting exposure assessment, as well as in the generation of data for determining exposure to both humans and the environment as well as assessing hazardous properties. This is a crucial prerequisite for carrying out a meaningful assessment of the risks. Further testing strategies are required to be established to cover all relevant endpoints needed for a risk assessment. At present, carrying out risk assessment of nanoparticles can only sensibly be done on a case-by-case basis. Only when more data becomes available may it be possible to group nanomaterials according to their physical, chemical and/or biological properties or mode of action, so that testing could be done for representatives of each group."
The massive review (426 pages) first provides context for the four groups of materials chosen – fullerenes, carbon nanotubes, metals and metal oxides – in terms of production techniques, applications and market value.
It then highlights the essential role which nanoparticle characterization plays in a variety of overlapping contexts ranging from fundamental and applied research, through process and product quality control and commercialization, to health and environmental protection.
In the context of exposure assessment, the review shows that there is, in general, a paucity of published data. The authors make recommendations for further occupational, consumer and environmental exposure assessment to support effective risk assessment and characterization
Similarly, the review highlights the general paucity of data in the area of environmental fate and behavior, which represents a major obstacle in developing a holistic view of the fate and transport of nanomaterials within the environment and therefore environmental exposure.
The review then goes on to present a substantial appraisal of the toxicity of nanoparticles for each of the four nanomaterial classes covered, considering the latest studies which have sought to assess the toxicity of nanomaterials including the utilization of both in vivo (within mice and rats) and in vitro models (using cell lines and primary cells). It evaluates their toxic potential and identifies the underlying mechanisms driving each of their toxicities, and determines whether any generalizations can be made regarding nanomaterials as a whole.
Finally, based on the information provided so far, the authors presents a basic risk assessment, inspired by the REACH Guidance, for the four types of nanomaterials under review. This includes an assessment for both the human health and the environment, limited to the extent that the available data allows. For each nanomaterial uncertainties and additional work needed to complete the assessment are also described.
One conclusion that the authors point out: "The risk assessments show a significant lack of measured and modeled exposure data of nanoparticles, for humans (occupational and consumer exposure) and for the environment."