Oxidative and Toxicological Evolution of Engineered Nanoparticles with Atmospherically Relevant Coatings

PM2.5 and the typical components cause organelle damage, apoptosis and necrosis: Role of reactive oxygen species

In this research, the organelle damage, apoptosis and necrosis induced by PM_2.5, BC and Kaolin were studied using human bronchial epithelial (16HBE) cells. PM_2.5, BC and Kaolin all induce cell death, LDH release and excess intracellular ROS generation. For the organelle injuries, Kaolin and high-dose PM_2.5 (240 μg/mL) cause lysosomal acidification, but BC causes lysosomal alkalization (lysosomal membrane permeabilization, LMP). BC and Kaolin cause the loss of mitochondrial membrane potential (MMP), while PM_2.5 does not. For the cell death mode, PM_2.5 causes both apoptosis and necrosis. However only necrosis has been detected in the BC and Kaolin treated groups, indicating the more severe cellular insult. Excess ROS generation is involved in the organelle damage and cell death. ROS contributes to the BC-induced LMP and necrosis, but does not significantly affect the Kaolin-induced MMP loss and necrosis. Therefore, the BC component in PM_2.5 may cause cytotoxicity via ROS-dependent pathways, the Kaolin component may damage cells via ROS-independent mechanisms such as strong interaction. The PM_2.5-induced apoptosis and necrosis can be partially mitigated after the removal of ROS, indicating the existence of both the ROS-dependent and ROS-independent mechanisms due to the complicated PM_2.5 components. BC represents the anthropogenic source component in PM_2.5, while Kaolin represents the natural source component. Our results provide knowledge on the toxic mechanisms of typical PM_2.5 components at the cellular and subcellular levels.

Proteome-wide effects of naphthalene-derived secondary organic aerosol in BEAS-2B cells are caused by short-lived unsaturated carbonyls

Exposure to air pollution causes adverse health outcomes, but the toxicity mechanisms remain unclear. Here, we investigated the dynamic toxicities of naphthalene-derived secondary organic aerosol (NSOA) in a human bronchial epithelial cell line (BEAS-2B) and identified the chemical components responsible for toxicities. The chemical composition of NSOA was found to vary with six simulated atmospheric aging conditions (C₁-C₆), as characterized by high-resolution mass spectrometry and ion mobility mass spectrometry. Global proteome profiling reveals dynamic evolution in toxicity: Stronger proteome-wide impacts were detected in fresh NSOA, but the effects declined along with atmospheric aging. While Nrf2-regulated proteins (e.g., NQO1) were significantly up-regulated, the majority (78 to 97%) of proteins from inflammation and other pathways were down-regulated by NSOA exposure (e.g., Rho GTPases). This pattern is distinct from the reactive oxygen species (ROS)-mediated toxicity pathway, and an alternative cysteine reaction pathway was revealed by the decreased abundance of proteins (e.g., MT1X) prone to posttranslational thiol modification. This pathway was further validated by observing decreased Nrf2 response in reporter cells, after preincubating NSOA with cysteine. Ethynyl-naphthalene probe was employed to confirm the alkylation of cellular proteome thiols on the proteome-wide level by fresh NSOA via in-gel fluorescence imaging. Nontarget analysis identified several unsaturated carbonyls, including naphthoquinones and hydroxylated naphthoquinones, as the toxic components responsible for cysteine reactivity. Our study provides insights into the dynamic toxicities of NSOA during atmospheric aging and identifies short-lived unsaturated carbonyls as the predominant toxic components at the posttranslational level.

Associations between source-resolved PM2.5 and airway inflammation at urban and rural locations in Beijing

BACKGROUND

A large number of research studies have explored the health effects of exposure to atmospheric particulate matter. However, limited quantitative evidence has linked specific sources of personal PM_2.5 directly to adverse health effects. This study was conducted in order to examine the association between airway inflammation and personal exposure to PM_2.5 mass, components, and sources among two healthy cohorts living in both urban and rural areas of Beijing, China.

METHODS

We conducted a follow-up study during the summer of 2016 and the winter of 2016/2017 among 92 students and 43 guards. 24-h personal and ambient exposure to PM_2.5 and fractional exhaled nitric oxide (FeNO) were measured at least twice for each participant. Chemical components of 385 personal PM_2.5 exposure samples were analyzed, and pollution sources were resolved by a positive matrix factorization (PMF) receptor model. We have constructed linear mixed effect models to evaluate the association between ambient/personal PM_2.5 mass, chemical constituents, and source specific PM_2.5 with FeNO after controlling for temperature, relative humidity, sites, season, and potential individual confounders.

RESULTS

Interquartile range (IQR) increase in household heating sources was associated with increased FeNO (2.72%; 95% CI = 1.26-4.17%) across two sites. IQR increase in roadway transport was associated with increased FeNO (9.84%; 95% CI = 2.69-17%) in urban areas; IQR increase in Secondary inorganic sources and Industrial/Combustion sources were associated with increased FeNO (7.96%; 95% CI = 1.47-14.4%% and 7.85%; 95% CI = 0.0676-15.6%, respectively) in rural areas. Personal exposure to EC, OC, and some trace elements (Se, Pb, Bi, Cs) were also estimated to be significantly associated with the increase of FeNO. In addition, there was no significant difference (P > 0.05) between the effects of ambient and personal PM_2.5 mass.

CONCLUSIONS

Although personal PM_2.5 mass was not significantly associated with the health effects, airway inflammation can be linked to source-resolved exposures.

Evaporation of Metals during the Thermal Treatment of Oxide Nanomaterials in Cellulose-Based Matrices

Like conventional material products, waste is the last stage of the life cycle of engineered nanomaterials, which are then incinerated or stabilized before disposal. However, because of their special physical characteristics, the fate of the thermally treated nanomaterials may differ or not from the conventional ones. In this study the thermal release of metals from three nanomaterials, namely CuO, ZnO, and TiO₂, embedded in matrices containing organic and inorganic compounds was investigated by using an in-house developed setup. The latter, which combines a TGA (Thermogravimetric Analyzer) and an ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometer), offers the possibility to gain simultaneously thermogravimetric and elemental information. It is shown that the matrix composition, such as chlorine and silicon, plays a key role in the evaporation of Cu and Zn at temperatures above 700 °C, while at relatively low temperatures (250 to 450 °C) the nanomaterials are most probably entrained in the flue gas independently of their chemical properties. Incineration experiments using a tubular furnace and subsequent ICP-MS (ICP Mass Spectrometry) analysis of the obtained residues allowed for quantification of the metal evaporation from the three nanomaterials.

Experimental Study of OH-Initiated Heterogeneous Oxidation of Organophosphate Flame Retardants: Kinetics, Mechanism, and Toxicity

The environmental risks and health impacts associated with particulate organophosphate flame retardants (OPFRs), which are ubiquitous in the global atmosphere, have not been adequately assessed due to the lack of data on the reaction kinetics, products, and toxicity associated with their atmospheric transformations. Here, the importance of such transformations for OPFRs are explored by investigating the reaction kinetics, degradation chemical mechanisms, and toxicological evolution of two OPFRs (2-ethylhexyl diphenyl phosphate (EHDP) and diphenyl phosphate (DPhP)) coated on (NH₄)₂SO₄ particles upon heterogeneous OH oxidation. The derived reaction rate constants for the heterogeneous loss of EHDP and DPhP are (1.12 ± 0.22) × 10^-12 and (2.33 ± 0.14) × 10^-12 cm³ molecules^-1 s^-1, respectively. Using recently developed real-time particle chemical composition measurements, particulate products from heterogeneous photooxidation and the associated degradation mechanisms for particulate OPFRs are reported for the first time. Subsequent cytotoxicity analysis of the unreacted and oxidized OPFR particles indicated that the overall particle cytotoxicity was reduced by up to 94% with heterogeneous photooxidation, likely due to a significantly lower cytotoxicity associated with the oxidized OPFR products relative to the parent OPFRs. The present work not only provides guidance for future field sampling for the detection of transformation products of OPFRs, but also strongly supports the ongoing risk assessment of these emerging chemicals and most critically, their products.

Understanding the Impact of Relative Humidity and Coexisting Soluble Iron on the OH-Initiated Heterogeneous Oxidation of Organophosphate Flame Retardants

The current uncertainties in the reactivity and atmospheric persistence of particle-associated chemicals present a challenge for the prediction of long-range transport and deposition of emerging chemicals such as organophosphate flame retardants, which are ubiquitous in the global environment. Here, the OH-initiated heterogeneous oxidation kinetics of organophosphate flame retardants (OPFRs) coated on inert (NH₄)₂SO₄ and redox-active FeSO₄ particles were systematically determined as a function of relative humidity (RH). The derived reaction rate constants for the heterogeneous loss of tricresyl phosphate (TCP; k_TCP) and tris(2-butoxyethyl) phosphate (TBEP; k_TBEP) were in the range of (2.69-3.57) × 10^-12 and (3.06-5.55) × 10^-12 cm³ molecules^-1 s^-1, respectively, depending on the RH and coexisting Fe(II) content. The k_TCP (coated on (NH₄)₂SO₄) was relatively constant over the investigated RH range while k_TBEP was enhanced by up to 19% with increasing RH. For both OPFRs, the presence of Fe(II) enhanced their k by up to 53% over inert (NH₄)₂SO₄. These enhancement effects (RH and Fe(II)) were attributed to fundamental changes in the organic phase state (higher RH lowered particle viscosity) and Fenton-type chemistry which resulted in the formation of reactive oxygen species, respectively. Such findings serve to emphasize the importance of ambient RH, the phase state of particle-bound organics in general, and the presence of coexisting metallic species for an accurate description of the degradation kinetics and aging of particulate OPFRs in models used to evaluate their atmospheric persistence.