Research Strategies for Safety Evaluation of Nanomaterials, Part

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IV: Risk Assessment of Nanoparticles

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2583

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ENVIRON International Corporation

2006

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Nanoparticles are small-scale substances (<100 nm) with unique properties and, thus, complex

exposure and health risk implications.

This symposium review summarizes recent findings in exposure and toxicity of nanoparticles and

their application for assessing human health risks. Characterization of airborne particles indicates

that exposures will depend on particle behavior (e.g., disperse or aggregate) and that accurate,

portable, and costeffective measurement techniques are essential for understanding exposure.

Under many conditions, dermal penetration of nanoparticles may be limited for consumer products

such as sunscreens, although additional studies are needed on potential photooxidation products,

experimental methods, and the effect of skin condition on penetration. Carbon nanotubes

apparently have greater pulmonary toxicity (inflammation, granuloma) in mice than fine-scale

carbon graphite, and their metal content may affect toxicity.

Studies on TiO2 and quartz illustrate the complex relationship between toxicity and particle

characteristics, including surface coatings, which make generalizations (e.g., smaller particles are

always more toxic) incorrect for some substances. These recent toxicity and exposure data,

combined with therapeutic and other related literature, are beginning to shape risk assessments that

will be used to regulate the use of nanomaterials in consumer products.

Key Words: nanotechnology; nanoparticles; risk assessment; exposure assessment.