Carcinogenicity of inhaled nanoparticles

Area of Science:

• Environmental Health
• Toxicology
• Nanomaterial Safety

Background:

• Epidemiological studies link ambient fine particulate matter (PM2.5) to elevated lung cancer risk.
• The carcinogenicity of diesel exhaust particles, partly due to their small size, is well-documented.
• Existing risk assessments struggle to explain the observed lung cancer risks solely by adsorbed organic compounds or metals.

Purpose of the Study:

• To investigate the carcinogenic potential of ultrafine synthetic nanoparticles.
• To evaluate if particle size and composition, independent of adsorbed toxins, contribute to lung cancer.
• To assess if bio-durable nanoparticles meet criteria for carcinogenic substances.

Main Methods:

• Inhalation studies with rats exposed to diesel particles and synthetic nanoparticles (carbon black, titanium dioxide).
• Intratracheal instillation studies with various synthetic nanoparticles.
• Review of in vitro genotoxicity data for nanomaterials.
• Comparison with International Agency for Research on Cancer (IARC) classifications.

Main Results:

• Diesel particles and synthetic nanoparticles showed carcinogenic effects in rat inhalation studies.
• Studies with synthetic nanoparticles virtually free of organic compounds corroborated the role of particle size.
• Long-term intratracheal instillation studies confirmed carcinogenicity for a broad range of synthetic nanoparticles.
• In vitro genotoxicity data for TiO(2) and carbon black nanomaterials have increased.

Conclusions:

• There is clear evidence of carcinogenicity in rats for bio-durable nanoparticles.
• The findings support the hypothesis that particle size is a significant factor in lung cancer risk.
• Bio-durable nanoparticles meeting these criteria fulfill the European Union's classification for category 2 carcinogens.