Influence of ozone initiated processing on the toxicity of aerosol particles from small scale wood combustion

Erik Z Nordin,Oskari Uski,Robin Nyström,Pasi Jalava,Axel C Eriksson,Johan Genberg,Pontus Roldin,Christoffer Bergvall,Roger Westerholm,Jorma Jokiniemi,Joakim H Pagels,Christoffer Boman,Maija-Riitta Hirvonen

doi:10.1016/j.atmosenv.2014.11.068

Abstract

Black carbon containing emissions from biomass combustion are being transformed in the atmosphere upon processing induced by tropospheric ozone and UV. The knowledge today is very limited on how atmospheric processing affects the toxicological properties of the emissions.The aim of this study was to investigate the influence of ozone initiated (dark) atmospheric processing on the physicochemical and toxicological properties of particulate emissions from wood combustion.Emissions from a conventional wood stove operated at two combustion conditions (nominal and hot air starved) were diluted and transferred to a chamber. Particulate matter (PM) was collected before and after ozone addition to the chamber using an impactor. Detailed chemical and physical characterization was performed on chamber air and collected PM. The collected PM was investigated toxicologically in vitro with a mouse macrophage model, endpoints included: cell cycle analysis, viability, inflammation and genotoxicity.The results suggest that changes in the organic fraction, including polycyclic aromatic hydrocarbons (PAHs) are the main driver for differences in obtained toxicological effects. Fresh hot air starved emissions containing a higher organic and PAH mass-fraction affected cell viability stronger than fresh emissions from nominal combustion. The PAH mass fractions decreased upon aging due to chemical degradation. Dark aging increased genotoxicity, reduced viability and reduced release of inflammatory markers. These differences were statistically significant for single doses and typically less pronounced. We hypothesize that the alterations in toxicity upon simulated dark aging in the atmosphere may be caused by reaction products that form when PAHs and other organic compounds react with ozone and nitrate radicals.

Highlights

IntroductionExposure to small scale biomass combustion aerosol is considered a major health issue globally
The results suggest that changes in the organic fraction, including polycyclic aromatic hydrocarbons (PAHs) are the main driver for differences in obtained toxicological effects
We hypothesize that the alterations in toxicity upon simulated dark aging in the atmosphere may be caused by reaction products that form when Polycyclic aromatic hydrocarbons (PAHs) and other organic compounds react with ozone and nitrate radicals

Summary

Introduction

Exposure to small scale biomass combustion aerosol is considered a major health issue globally. There is cumulative evidence from both in vitro and in vivo experiments including controlled human exposure studies, where exposure to fresh biomass combustion particles from incomplete combustion conditions, have been shown to cause adverse health effects. Polycyclic aromatic hydrocarbons (PAHs) are suspected to be mediators of adverse health effects in exposure to this kind of biomass combustion aerosol (Binkova et al, 2007). Several publications demonstrated that elevated levels of PAHs and soot (black carbon) are emitted from wood stoves operated at hot air starved conditions (Pettersson et al, 2011; Orasche et al, 2013; Eriksson et al, 2014)

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