The challenge of forecasting risk for a broad number of materials is further complicated by large degrees of uncertainty concerning production amounts, the characteristics and uses of these materials, exposure pathways, and a scarcity of data concerning the relationship between nanomaterial characteristics and their effects on organisms and ecosystems.
There have been very few studies evaluating the factors controlling environmental exposure despite the fact that risk management strategies for nanomaterials, where needed, are likely to depend on exposure management. A risk management strategy rooted in a fundamental understanding of the possible pathways of exposure to nanomaterials leads to a broad array of options for managing risk, that spans from protective devices for workers in nanomaterial fabrication industries, to standards for product disposal or recycling, the use of pollution reduction equipment, changes in human behavior and, in extreme cases, an outright ban on the production of a given nanomaterial.
Due to the large number of possibilities for taking action early in the trajectory of a technology, managing exposure as the basis for risk management of an emerging technology such as nanotechnologies will likely prove to be more robust and successful. Exposure assessments based on quantities likely to be produced, project routes of exposure and persistence provide an immediate basis for identifying possible problems. Important questions to be answered in evaluating nanomaterial risk are therefore related to the format that nanomaterials will be present in as commercial products, the potential for these materials to be released to the environment, and the transformations that those materials may undergo that affect their transport and potential for exposure.
The PRA 5include the following six key features:
1) the ability to generate forecasts and associated levels of uncertainty for questions of immediate concern,
2) a consideration of all pertinent sources of nanomaterials,
3) an inclusive consideration of the impacts of activities stemming from nanomaterial use and production that extends beyond the boundaries of toxicology and include full life cycle impacts,
4) the ability to adapt and update risk forecasts as new information becomes available,
5) feedback to improve information gathering and, 6) feedback to improve nanomaterial design.
Feature 6 implies that the potential risks of nanomaterials must ultimately be determined as a function of fundamental, quantifiable properties of nanomaterials, so that when these properties are observed in a new material, they can be recognized as indicators of risk.