title: Mass or total surface area with aerosol size distribution as exposure metrics for inflammatory, cytotoxic and oxidative lung responses in rats exposed to titanium dioxide nanoparticles.
abstract: There is currently no consensus on the best exposure metric(s) for expressing nanoparticle (NP) dose. Although surface area has been extensively studied for inflammatory responses, it has not been as thoroughly validated for cytotoxicity or oxidative stress effects. Since inhaled NPs deposit and interact with lung cells based on agglomerate size, we hypothesize that mass concentration combined with aerosol size distribution is suitable for NP risk assessment. The objective of this study was to evaluate different exposure metrics for inhaled 5 nm titanium dioxide aerosols composed of small (SA < 100 nm) or large (LA > 100 nm) agglomerates at 2, 7, and 20 mg/m3on rat lung inflammatory, cytotoxicity, and oxidative stress responses. We found a significant positive correlation ( r = 0.98, p < 0.01) with the inflammatory reaction, measured by the number of neutrophils and the mass concentration when considering all six (SA + LA) aerosols. This correlation was similar ( r = 0.87) for total surface area. Regarding cytotoxicity and oxidative stress responses, measured by lactate dehydrogenase and 8-isoprostane, respectively, and mass or total surface area as an exposure metric, we observed significant positive correlations only with SA aerosols for both the mass concentration and size distribution ( r > 0.91, p < 0.01), as well as for the total surface area ( r > 0.97, p < 0.01). These data show that mass or total surface area concentrations alone are insufficient to adequately predict oxidant and cytotoxic pulmonary effects. Overall, our study indicates that considering NP size distribution along with mass or total surface area concentrations contributes to a more mechanistic discrimination of pulmonary responses to NP exposure.
authors.affiliation: 1 Département de santé environnementale et de santé au travail, Institut de recherche en santé publique, Université de Montréal, Montréal, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Noël
authors.affiliation: 2 Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST), Montréal, Canada.
authors.forename: G
authors.initials: G
authors.lastname: Truchon
authors.affiliation: 2 Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST), Montréal, Canada.
authors.forename: Y
authors.initials: Y
authors.lastname: Cloutier
authors.affiliation: 3 INRS-Institut Armand-Frappier, Université du Québec, Laval, Canada.|Deceased.
authors.forename: M
authors.initials: M
authors.lastname: Charbonneau
authors.affiliation: 4 Centre de recherche de l'Hôpital du Sacré-Cœur de Montréal, Université de Montréal, Montréal, Canada.
authors.forename: K
authors.initials: K
authors.lastname: Maghni
authors.affiliation: 1 Département de santé environnementale et de santé au travail, Institut de recherche en santé publique, Université de Montréal, Montréal, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Tardif
mesh_terms: D000336:Aerosols; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D016923:Cell Death / Q000187:drug effects; D015237:Dinoprost / Q000031:analogs & derivatives / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D019570:Inhalation Exposure; D008168:Lung / Q000187:drug effects* / Q000276:immunology; D008297:Male; D053768:Metal Nanoparticles / Q000008:administration & dosage / Q000737:chemistry / Q000633:toxicity* / Q000648:ultrastructure; D020556:Neutrophil Infiltration / Q000187:drug effects; D016877:Oxidants / Q000008:administration & dosage / Q000737:chemistry / Q000633:toxicity*; D018384:Oxidative Stress / Q000187:drug effects; D010316:Particle Size; D011916:Rats, Inbred F344; D020545:Respiratory Mucosa / Q000187:drug effects* / Q000276:immunology; D013499:Surface Properties; D014025:Titanium / Q000008:administration & dosage / Q000737:chemistry / Q000633:toxicity*; D023382:Toxicity Tests, Acute / Q000379:methods*
chemical_list: D000336:Aerosols; D015415:Biomarkers; D016877:Oxidants; C009495:titanium dioxide; C075750:8-epi-prostaglandin F2alpha; D015237:Dinoprost; D014025:Titanium
keywords: Titanium dioxide; exposure metric; nanoparticle; nanotoxicology; pulmonary toxicity