Ultrafine particles and health: aligning size distributions and chemical composition for more comprehensive risk assessment

Abstract

Atmospheric ultrafine particles (UFP, aerodynamic diameter ≤ 100 nm) are an emerging global air quality and public health concern. UFP dominate ambient particle number concentrations while constituting only a minor fraction of particulate mass. Their small sizes and high specific surface areas promote deep lung deposition, translocation, and the adsorption of redox-active substances like organics and transition metals, contributing to their adverse health impacts. In this perspective, we summarized epidemiological and toxicological studies of UFP, highlighting the discrepancies in the nanotoxicity using number-, versus surface area-based dose metrics. Current studies have linked UFP exposure to increased respiratory, cardiovascular, and central nervous system mortalities and morbidities, both short term and long term. In addition, surface area-based metric captured stronger associations with natural mortality and cardiovascular-related hospital admissions than number concentration, suggesting particle surface area might better reflect the toxic potential of UFP. However, current literature cannot support definitive associations, because of the dynamic nature of UFP, confounding co-pollutants, and differed measurement techniques. Advancing UFP health science and policy requires coordinated particle size distribution monitoring that reports both particle number and surface concentrations. These measurements are essential for comprehensive risk assessment, exposure modeling, and ultimately for evidence-based air quality standards capable of addressing the distinct hazards posed by UFP.

Graphical abstract

Keywords

Ultrafine particles / Air pollution / Atmospheric toxicity / Nanotoxicity / Health effects

Highlight

	● Size distribution information is needed to better capture UFP health effects.
	● Epidemiological studies link UFP to respiratory, cardiovascular, and dementia diseases.
	● Toxicology study shows UFP inhalation targets lung, and translocate to heart and brain.
	● Chemically, enriched carbon and transition metals in UFP exhibit greater toxicity.

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