As new materials and products are developed, it is important to know the potential health and environmental risks they may have. In the workplace, occupational exposure limits (OEL) are put in place in order to prevent the worker from handling the material in such a way that may cause harm to them. According to the CDC, "Even though there is so far not much evidence that simply being nanosized [can] lead to toxicological properties that are different from the bulk material or unique for the nanosize, many studies have shown that nanoscale particles can be more biologically active such as eliciting greater pulmonary inflammation at a given mass dose."
Since studies of nanomaterials are fairly new, the toxicity information gathered about these materials comes mainly from the testing of animals or in vitro studies. The testing of animals can take years which makes it difficult to stay up to date with the fast growing number of nanomaterials. For this reason, scientists have suggested other ways of conducting risk assessment for nanomaterials. The World Health Organization (WHO) has set out to identify these proposed risk assessment strategies in order to create a WHO guideline for working with nanomaterials.
Perhaps the most feasible approach is the one which is being done for nanofibers where the properties of the new material is compared to those of a known material (ex. Nanofibers) and to assume the toxicity will be similar. This strategy is known as "bridging" or "read across". Another proposed strategy is known as "grouping" and involves making groups of nanomaterials which have similar toxicity. For example, chemicals which have been shown to cause cancer would be grouped together. It could be assumed that their toxic effects might increase when nanosized, due to increased surface area. Yet other proposed strategies look at air pollution research or the chemical structure of the material [Quantitative Structure-Activity Relationship (QSAR)].
As you can see, the strategies being used to assess the possible health and environmental risks of nanomaterials are numerous and varied. It is challenging to find a strategy which is agreed upon to find the OELs for nanomaterials and to validate the findings with empirical data. Until a standard is developed for OELs for nanomaterials, there are benchmark levels to which exposure levels measured in occupational setting can be compared.