7. What do we still need to know?
Research needs identified by CSRSEN in 2007 are still valid. They include
- The availability of validated in vitro assays
- Developing understanding of quantitative structure activity relationships
- Studies on potential cardiovascular effects
- Evaluation of bacterial genotoxicity assays
- Methods for predicting of environmental concentrations
- Identifying environmental species for ecotoxicity testing
Since the CSRSEN first looked into it, there has been quite a lot more work on evaluating possible harmful effects of nanomaterials, especially using laboratory tests (in vitro assays). They are useful for screening and for investigating mechanisms of adverse effects. However, tests using living organisms (in vivo assays) are also needed to improve knowledge of possible risks to people and the environment. Further improvements are also sought in refining exposure doses, and there is an urgent need for long-term exposure studies.
Some progress has been made on properties to be determined for nanomaterial characterisation, toxicokinetics and genotoxicity testing with mammalian cells, and environmental behaviour of nanomaterials. Recent research has also identified new concerns in the areas of protein fibrillation, potential hazards of certain nanotubes, and potential for transfer across the food chain in environmental species.
There is an extensive range of additional research needs. Characterisation of nanomaterials will be improved by urgently needed development of reference materials for evaluation of measurement techniques and comparison of biological responses. Exposure measurements demand better methods for distinguishing between background and manufactured nanomaterials in the workplace or the environment. The effects of nanoparticles on protein behaviour need further investigation, to see if effects found in laboratory preparations occur in living organisms. And there is a need for more work on possible effects in the brain relevant to amyloid diseases and on the potential hazards of nanofibres and tubes.
In study of environmental exposures, the most urgent need is for methods to detect and measure ambient concentrations of free nanomaterials. However, there is a lengthy agenda for further work on assessing potential environmental hazards of nanomaterials. It includes theoretical work to predict exposure levels of nanomaterials in water, to improve imperfect understanding of relative affinities for liquids and solids.