Differential In Vitro Lung Cell Toxicity of Fresh and Photochemically Aged Smoke Aerosol Emissions from Simulated Wildland Fires of Duff and Surface Fuels

TL;DR

This study shows that smoke from simulated wildland fires affects lung cells differently depending on fuel moisture and whether the smoke is aged in the atmosphere.

Contribution

The study reveals that photochemical aging reduces the oxidative potential of wildfire smoke, while prescribed fire smoke is more toxic.

Findings

PM extracts from all fire types induced oxidative stress in lung cells, but Wild-Aged smoke showed reduced toxicity.

Prescribed fire (Rx) smoke was more toxic than wildfire (Wild) smoke based on cell damage and gene expression.

Toxicity was linked to aromatic compounds in PM, with the highest levels in Rx smoke.

Abstract

We investigated the
effects of the fuel moisture content
and photochemical
aging on the toxicity of smoke particulate matter (PM) emissions in
simulated wildland fires. We burned fuel beds consisting of surface
fuels and duff under moderate and low moisture contents, representative
of prescribed fires (Rx) and drought-induced wildfires (Wild), respectively.
The Wild emissions were photochemically aged in an oxidation flow
reactor (Wild-Aged). We exposed human bronchial epithelial cells to
PM extracts from each permutation. PM extracts from all experimental
permutations (Rx, Wild, Wild-Aged) induced oxidative stress, evidenced
by a significant increase in 8-isoprostane concentration in the cell
media compared to control. However, the increase of 8-isoprostane
was significantly less in Wild-Aged compared to that in Wild and Rx,
indicating loss of oxidative potential due to photochemical aging.
Based on the release of lactate dehydrogenase in the cell media, the
level of lipid peroxidation, and the magnitude of gene fold-changes,
Rx PM extracts were more toxic than Wild. Chemical composition analysis
suggests that toxicity was driven by levels of aromatic species in
the PM, which were highest in Rx, followed by Wild and Wild-Aged.
Overall, these results highlight the complex dependence of the toxicity
of wildland-fire smoke on combustion conditions and atmospheric processing.

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