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Updated: Aug 16, 2025
Murine Model of Allergen Induced Asthma
Published on: May 14, 2012
Indoor PM2.5 from occupied residences in Sweden caused higher inflammation in mice compared to outdoor PM2.5
Aneta Wierzbicka1,2, Yuliya Omelekhina1,2, Anne Thoustrup Saber3
1Ergonomics and Aerosol Technology, Lund University, Lund, Sweden.
Abstract:
We spend most of our time indoors; however, little is known about the effects of exposure to aerosol particles indoors. We aimed to determine differences in relative toxicity and physicochemical properties of PM2.5 collected simultaneously indoors (PM2.5 INDOOR ) and outdoors (PM2.5 OUTDOOR ) in 15 occupied homes in southern Sweden. Collected particles were extracted from filters, pooled (indoor and outdoor separately), and characterized for chemical composition and endotoxins before being tested for toxicity in mice via intratracheal instillation. Various endpoints including lung inflammation, genotoxicity, and acute-phase response in lung and liver were assessed 1, 3, and 28 days post-exposure. Chemical composition of particles used in toxicological assessment was compared to particles analyzed without extraction. Time-resolved particle mass and number concentrations were monitored. PM2.5 INDOOR showed higher relative concentrations (μg mg-1 ) of metals, PAHs, and endotoxins compared to PM2.5 OUTDOOR . These differences may be linked to PM2.5 INDOOR causing significantly higher lung inflammation and lung acute-phase response 1 day post-exposure compared to PM2.5 OUTDOOR and vehicle controls, respectively. None of the tested materials caused genotoxicity. PM2.5 INDOOR displayed higher relative toxicity than PM2.5 OUTDOOR under the studied conditions, that is, wintertime with reduced air exchange rates, high influence of indoor sources, and relatively low outdoor concentrations of PM. Reducing PM2.5 INDOOR exposure requires reduction of both infiltration from outdoors and indoor-generated particles.
Insights
Indoor fine particulate matter (PM2.5) is more toxic than outdoor PM2.5, causing greater lung inflammation. Reducing indoor PM2.5 requires addressing both outdoor infiltration and indoor sources.
Area of Science:
- Environmental Health
- Toxicology
- Air Quality
Background:
- Most human exposure to particulate matter (PM2.5) occurs indoors, yet its health effects are less understood than outdoor PM.
- Indoor PM2.5 composition and toxicity can differ significantly from outdoor PM2.5.
Purpose of the Study:
- To compare the relative toxicity and physicochemical properties of indoor PM2.5 (PM2.5 INDOOR) and outdoor PM2.5 (PM2.5 OUTDOOR).
- To investigate the health impacts of indoor versus outdoor PM2.5 exposure in a controlled mouse model.
Main Methods:
- Simultaneous collection of PM2.5 from 15 homes in southern Sweden.
- Characterization of PM2.5 for chemical composition (metals, PAHs, endotoxins) and toxicity testing in mice via intratracheal instillation.
- Assessment of lung inflammation, genotoxicity, and acute-phase responses at multiple time points post-exposure.
Main Results:
- PM2.5 INDOOR exhibited higher relative concentrations of metals, polycyclic aromatic hydrocarbons (PAHs), and endotoxins compared to PM2.5 OUTDOOR.
- PM2.5 INDOOR induced significantly higher lung inflammation and acute-phase responses 1 day post-exposure compared to PM2.5 OUTDOOR.
- No genotoxicity was observed for either indoor or outdoor PM2.5 samples.
Conclusions:
- Indoor PM2.5 demonstrated higher relative toxicity than outdoor PM2.5 under winter conditions with reduced ventilation and high indoor source influence.
- Reducing indoor PM2.5 exposure necessitates strategies to mitigate both infiltration of outdoor particles and emissions from indoor sources.
