Table 1.

Summary recommendations regarding exposure conditions used in assessing ENM hazard potentials for model organisms

Develop logically conceived, plausible exposure and receptor scenarios in designing experiments, addressing background chemical, physical, and biotic conditions, biological endpoints, and exposure periods.

Thoroughly characterize exposure media, including natural soils, waters, and sediments, and provide metadata to allow cross-comparisons and for mining influential factors across studies.

Select ENM forms—including ENM mixtures or other co-contaminants—and scale exposure concentrations to logically well-defined exposure scenarios, or to scenario-independent mechanistic and process-based modeling goals, or to best available analytical instrumentation limitations.

To the fullest extent possible, characterize ENMs under the exposure conditions and over the time frame of hazard assessments to allow homogeneous exposure or understanding bioavailability and relating endpoint measures to effective forms.

Examine and choose multiple endpoints for ENM physicochemical characterization, toxicity quantification, and toxicant characterization, subject to the exposure scenario or similar context.

Quantify body burden and determine compartmentalization of ENMs and transformation products in receptors, to allow comparing effective doses to measured biological responses. Carefully consider body burden assay approaches to avoid artifacts.

Adopt appropriate experimental control treatments for media additives such as dispersants, and for ENM transformation products that are expected during hazard assessment.

Incorporate appropriate rapid screening approaches, as prioritized tiers in an ecological hazard assessment hierarchy (Fig. 1).

Adapt these approaches in response to relevant knowledge generation.