Polycyclic aromatic compounds (PACs) are organic pollutants associated with incomplete combustion processes and connected to severe health effects. Their connection to micro-nanoplastics (MNPs) emitted as particulate matter from incineration of plastics remains poorly explored. In this study, we detected 65 Polycyclic Aromatic Hydrocarbon (PAH), oxygenated (OPAH) and nitrated (NPAH) PAC species in MNPs emitted during the incineration of three widely used plastic materials, high-density polyethylene (HDPE), polypropylene (PP) and polyvinyl chloride (PVC). MNPs were generated using the incineration exposure generation system (INEXS) and their PAC profile was offline analyzed using gas chromatography-mass spectrometry. Notably, one of the most abundant species in all three plastics was Benzanthrone, an OPAH previously associated with traffic and biomass burning emissions. MNPs emitted by PVC incineration contained emerging highly toxic PAC species such as benzo(c)fluorene, dibenzopyrenes, and 6-nitrochrysene. Our findings highlight the importance of monitoring beyond the legacy 16 EPA members which accounted only by 12%, 47%, and 41% of the associated carcinogenic potency (expressed as BaPeq), for PVC, PP and HDPE respectively. These results raise concerns for potential health implications and underscore the urgent need for further research on this new environmental challenge, MNP pollution and its association with toxic persistent pollutants.

Due to the growth of urban areas in close proximity to wildlands, wildfires increasingly burn both biomass and man-made materials. The physicochemical properties of emitted particulate matter (PM) from such “wildland-urban interface (WUI)” fires may differ substantially from those of wildland fires and other ambient PM sources. However, the associations between properties and hazards of WUI fire PM have not been studied. Here, we employed a wildfire simulator (WiFS) to reproduce biomass and WUI fires by combusting pinewood and a simplistic WUI fire model (1:1 mixture of pinewood and polyethylene), respectively. WUI fire PM contained high concentrations of the highly toxic and carcinogenic PAH benzo[c]fluorene and significant amounts of highly bioactive alkyl and oxygenated PAHs, which were both absent in biomass fire PM, and had a carcinogenicity potential (benzo[a]pyrene equivalents, BaP_Eq) 20 times higher than biomass fire PM. Additionally, exposure of THP-1 macrophages to WUI fire PM, but not biomass fire PM, caused significant reductions in viability and mitochondrial potential, significantly decreased phagocytosis of 1 μm beads, and substantial dysregulation of gene expression. These findings suggest that WUI fire PM exposure may be more hazardous than wildland fire PM exposure, likely due to differences in their chemical profiles.

Wildfire particulate matter from Canadian forest fires significantly impacted the air quality in the northeastern United States during the summer of 2023. Here, we used real-time and time-integrated instrumentation to characterize the physicochemical properties and radiative effects of wildfire particulate matter reaching the metropolitan areas of New Jersey/ New York during this extreme incident. The radiative forcing of −352.4 W/m² derived here based on the measured optical properties of wildfire particulate matter explains, to some extent, the ground level temperature reduction of about 3 °C observed in New Jersey/ New York City during this incident. Such negative radiative forcing in densely populated megacities may limit natural ventilation, increase the residence time of wildfire particulate matter and background air pollutants, exacerbating public health risks. This study highlights the importance of radiative effects from wildfire particulate matter in densely populated areas and their potential implications for climate, air quality and public health.

Here, the light absorption of brown carbon (BrC) emitted by wood combustion and denuded from volatile organic carbon (VOC) at 300 °C is elucidated using a recently developed thermal decomposition platform coupled with a suite of real-time aerosol instrumentation and time-integrated sampling systems. The BrC particle size distribution, morphology and optical properties are closely controlled by increasing the combusted wood mass from 50 to 600 mg to emulate those measured for “real world” wildfire particulate matter (PM) emissions. Size-fractionation of such wildfire-like BrC reveals that the PM_0.1–2.5 fraction contains high molecular weight, carcinogenic polycyclic aromatic hydrocarbons (PAHs) and absorbs up to five times more light compared to the PM_0.1 fraction. Thus, increasing the combusted wood mass from 50 to 600 mg increases the PM_0.1–2.5 concentration by a factor of about eight and enhances the overall BrC mass absorption cross-section, MAC, up to a factor of two at a wavelength of 405 nm. Condensation of VOC on BrC reduces its MAC up to 40 %. Still, the particle size seems to largely determine the BrC light absorption, as large VOC-rich particles absorb more light compared to small VOC-lean ones. The size-resolved BrC MAC measured here can be interfaced with climate models to estimate the climate impact of wildfire PM emissions.