Pulmonary Toxicity of Combustion Byproducts from Lithium-Ion Battery Fires
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Background: The frequency of lithium-ion (Li-ion) battery-related fires is increasing globally, creating new challenges for firefighters and growing public safety concerns because they produce copious amounts of smoke and intense heat. Li-ion battery fires can quickly spread and are hard to extinguish with traditional methods. However, the effects of combustion byproducts from Li-ion battery fires on the respiratory system are not well understood.
Methods: We collected airborne smoke particulate matter (PM) during fires and post-fire soot samples resulting from Li-ion battery thermal runaway events (18650 cylindrical cells). Non-respirable particles with a diameter greater than 10 microns were removed through a filtration process. The soot and PM samples were chemically analyzed and assessed for lung toxicity and pulmonary function in CD-1 mice after oropharyngeal aspiration (100 µg of the smoke sample) at 4 and 24 h post-exposure. Lung toxicity outcomes were compared with those of a variety of air pollutant particles that were published in our previous papers. Chemical and biological results were further analyzed using a computational approach (R programing software) to identify hazardous chemical components driving toxicity outcomes.
Results: The soot sample contained more carbon species than the PM sample (37% vs. 17%) whereas more anions were measured in the PM sample (12% vs. 6%). Concentrations of inorganic elements (mostly Li and Ni) were similar (3%) on a mass basis between two smoke samples. Notably, fluoride which can cause various adverse health effects was found to be up to 5% of each sample. At 4 and 24 h post-exposure, both smoke samples caused significant increases in neutrophils, proinflammatory cytokines (IL-6 and MIP-2), and vascular injury biomarkers (protein and albumin). Cellular injury biomarkers (LDH and NAG) were also increased but not significantly. A significant increase in airflow obstruction (as measured by Penh) was observed at 4 and 24 h post-exposure to the soot and PM sample. The soot sample also significantly increased peak expiratory flow and decreased relaxation time. Comparing neutrophil data from this study to data published in our previous papers, the smoke soot and PM exhibited similar lung inflammatory outcomes caused by air pollutant samples from wildfires, diesel exhaust and coal-powered plant emissions. The data-driven computational analysis showed that F, Br, Co, Ni, and Li from both samples were key chemical contributors to the lung toxicity responses.
Conclusions: The findings show that (1) Li-ion battery fires can produce smoke and residual soot that contain hazardous heavy metals and fluoride, and (2) acute exposures to the smoke PM and soot can lead to airway constriction and lung inflammation in a similar fashion to other combustion-related air pollutants. Knowledge of the toxicity of combustion byproducts from Li-ion battery fires can inform communication strategies to advise first responders and the public to protect their health during these fire events.