Biokinetics of inhaled silver, gold, copper oxide, and zinc oxide nanoparticles: a review.

Summary

Across inhalation studies, silver and gold nanoparticles persist in lungs and secondary organs (liver, spleen, brain/olfactory bulb), with blood kinetics and organ deposition modulated by particle size. Copper oxide shows transient pulmonary retention and zinc oxide increases lung burden after short exposures only. These data highlight organ persistence and potential systemic exposure relevant to nano-enabled cosmetics and occupational settings.

Key Findings

• Silver and gold retained in lungs for >2,000 h and >672 h, respectively.
• Size-dependent blood persistence for gold: 4–13 nm elevated ≥672 h; 20–105 nm not elevated.
• Silver increased in liver and spleen up to 2,000 h; both Ag and Au increased in brain and olfactory bulb.
• CuO showed transient lung increase returning to baseline by ~500 h; ZnO increased lung burden after short-term exposure only.
• Overall biodistribution patterns were similar across materials, but Ag and Au showed notable long-term organ persistence.

Clinical Implications

For aerosolized cosmetic products and occupational handling, minimize inhalable fractions and prioritize larger particle sizes/coatings that reduce organ persistence; integrate size-specific risk communication and post-market surveillance.

Limitations

• Heterogeneous study designs and species limit quantitative synthesis.
• Limited human data and variability in nanoparticle coatings/surface chemistry.

Future Directions

Standardize inhalation exposure protocols and reporting (size, coating, dose metrics) with longitudinal human biomonitoring to inform regulatory thresholds.