Composition, characteristics, and treatment technologies of condensable particulate matter present in flue gas emitted by coking plants in China

To study the total particulate matter (TPM) in flue gas emitted by coking plants, a sampling system that could be used to collect filterable particulate matter (FPM) and condensable particulate matter (CPM) was designed and developed based on Method 202 recommended by the U.S. Environmental Protection Agency in 2017 and HJ 836-2017 issued by China. Using this system, FPM and CPM in flue gas emitted by four coking furnaces named A, B, C, and D were tested in China. Further, 9 water-soluble ions, 20 elements, and organic matter present in the CPM were simultaneously examined to determine their formation mechanisms. Statistical data suggested that the FPM emission level in the coking flue gas was low and the average mass concentration was less than 10 mg/m3. However, with high CPM and TPM emission levels, the TPM mass concentrations of A, B, C, and D were 130 ± 11.1, 84.4 ± 6.36, 35.1 ± 17.0, and 63.8 ± 13.0 mg/m3, respectively. The main component of TPM was CPM, and the average mass concentration of CPM accounted for 98%, 95%, 68%, and 95% of TPM in furnaces A, B, C, and D, respectively. Water-soluble ions were the important components of CPM, and the total concentration of water-soluble ions accounted for 70%, 87%, 42%, and 66% of CPM in furnaces A, B, C, and D, respectively. Toxic and harmful heavy metals, such as Mn, Cr, Ni, Cu, Zn, As, Cd, and Pb, were detected in CPM. The formation mechanism of CPM was analyzed in combination with flue-gas treatment. It was shown that the treatment process "activated carbon- flue-gas countercurrent-integrated purification technology + ammonia spraying" used in furnaces A and B was less effective in removing CPM, water-soluble ions, metals, and compounds than that of "selective catalytic reduction denitrification + limestone-gypsum wet desulfurization (spraying NaOH solution)" in furnaces C and D. Hence, different flue-gas treatment technologies and operation levels played vital roles in the formation, transformation, and removal of CPM from flue-gas. Organic components in CPM discharged from furnace A were determined via gas chromatography-mass spectrometry, and the top 15 organic components in CPM were obtained using the area normalization method. N-alkanes accounted for the highest proportion, followed by esters and phenols, and most of them were toxic and harmful to humans and ecosystems. Therefore, advanced CPM treatment technologies should be developed to reduce atmospheric PM2.5 and its precursors to improve ambient air quality in China.

Investigating environmentally persistent free radicals (EPFRs) emissions of 3D printing process

In recent years, the emission of particles and gaseous pollutants from 3D printing has attracted much attention due to potential health risks. This study investigated the generation of environmentally persistent free radicals (EPFRs, organic free radicals stabilized on or inside particles) in total particulate matter (TPM) released during the 3D printing process. Commercially available 3D printer filaments, made of acrylonitrile-butadiene-styrene (ABS) in two different colors and metal content, ABS-blue (19.66 μg/g Cu) and ABS-black (3.69 μg/g Fe), were used for printing. We hypothesized that the metal content/composition of the filaments contributes not only to the type and number of EPFRs in TPM emissions, but also impacts the overall yield of TPM emissions. TPM emissions during printing with ABS-blue (11.28 μg/g of printed material) were higher than with ABS-black (7.29 μg/g). Electron paramagnetic resonance (EPR) spectroscopy, employed to measure EPFRs in TPM emissions of both filaments, revealed higher EPFR concentrations in ABS-blue TPM (6.23 × 1017 spins/g) than in ABS-black TPM (9.72 × 1016 spins/g). The presence of copper in the ABS-blue contributed to the formation of mostly oxygen-centered EPFR species with a g-factor of ~2.0041 and a lifetime of 98 days. The ABS-black EPFR signal had a lower g-factor of ~2.0011, reflecting the formation of superoxide radicals during the printing process, which were shown to have an "estimated tentative" lifetime of 26 days. Both radical species (EPFRs and superoxides) translate to a potential health risk through inhalation of emitted particles.

A comparison of cigarette smoke test matrices and their responsiveness in the mouse lymphoma assay: A case study

No cigarette smoke test matrix is without limitation, due to the complexity of the starting aerosol and phase to phase dynamics. It is impossible to capture all chemicals at the same level of efficiency, therefore, any test matrix will inadvertently or by design fractionate the test aerosol. This case study examines how four different test matrices derived from cigarette smoke can be directly compared. The test matrices assessed were as follows, total particulate matter (TPM), gas vapour phase (GVP), a combination of TPM + GVP and whole aerosol (WA). Here we use an example assay, the mouse lymphoma assay (MLA) to demonstrate that data generated across four cigarette smoke test matrices can be compared. The results show that all test matrices were able to induce positive mutational events, but with clear differences in the biological activity (both potency and toxicity) between them. TPM was deemed the most potent test article and by extension, the particulate phase is interpreted as the main driver of genotoxic induced responses in the MLA. However, the results highlight that the vapour phase is also active. MLA appeared responsive to WA, with potentially lower potency, compared to TPM approaches. However, this observation is caveated in that the WA approaches used for comparison were made on a newly developed experimental method using dose calculations. The TPM + GVP matrix had comparable activity to TPM alone, but interestingly induced a greater number of mutational events at comparable relative total growth (RTG) and TPM-equivalent doses when compared to other test matrices. In conclusion, this case study highlights the importance of understanding test matrices in response to the biological assay being assessed and we note that not all test matrices are equal.

Effects of antioxidant capacity on micronucleus induction by cigarette smoke in mammalian cells

We have compared micronucleus (MN) induction by cigarette smoke in the L5178Y, TK6, and CHL/IU cell lines. The test sample was total particulate matter of 3R4F reference cigarette smoke, suspended in DMSO. After 3-h treatment, with or without a rat liver S9 metabolic activation system, followed by 24-h recovery, dose-dependent MN increases were seen in all cell lines. However, CHL/IU and TK6 cells were more resistant than L5178Y cells (comparison by Benchmark Doses with PROAST software). 3R4F smoke generates reactive oxygen species (ROS). Therefore, we explored the relationship between the sensitivities to 3R4F smoke and the antioxidant capacities of the cell lines. While the total antioxidant capacities were not significantly different among the cell lines, cellular glutathione (GSH) was higher in CHL/IU cells than in L5178Y cells. Pretreatment of CHL/IU cells with a GSH precursor, N-acetylcysteine (NAC), reduced the genotoxicity/cytotoxicity of 3R4F, whereas an inhibitor of GSH biosynthesis, buthionine sulfoximine (BSO), enhanced it. The effects of NAC and BSO were also seen after treatment with allyl isothiocyanate, a ROS-generating chemical, but not with mitomycin C, a ROS-independent genotoxicant. Pretreatment with NAC increased cellular thiol levels. From the present results, the genotoxicity and cytotoxicity of cigarette smoke differs among these cell lines in a manner that may be related to their antioxidant thiol levels.

Spatial and temporal trends in physiological biomarkers of adult eastern oysters, Crassostrea virginica, within an urban estuary

Heavy metal contamination and water quality may alter reproductive capacity of oysters in highly urbanized, eutrophic ecosystems. This study assessed physiological biomarkers and heavy metal body burdens in adult oysters, Crassostrea virginica, placed at a highly urban and reference site. Condition index and Vitellogenin-like proteins were significantly different between sites, but protein concentration and activity of the electron transport system were not. Accumulation of Cd and Hg occurred at both sites, and Cd body burden was greater at the urban site. There was a negative relationship between condition index and Cd body burden at the urban site, while no relationship was found between physiological biomarkers and metal burden at the reference site. The results suggest that oyster condition and reproductive potential may be negatively influenced by the biotic and abiotic factors typically found within urban, eutrophic ecosystems.

Accurate measurement of main aerosol constituents from heated tobacco products (HTPs): Implications for a fundamentally different aerosol

ISO 4387 Standard determines the main aerosol constituents (total particulate matter, water, nicotine, and nicotine-free-dry-particulate matter, referred to as "tar") in cigarette mainstream smoke (ISO, 2000). Heated Tobacco Products (also called Tobacco Heating Products or Heat-not-Burn Products) are designed to form aerosol by heating tobacco rather than burning like in combustible cigarettes. In this study we have evaluated the suitability of ISO 4387 Standard to be adapted for quantifying main aerosol constituents for HTP aerosol. HTP emissions have much higher levels of water and humectants (e.g., glycerol) in dynamic equilibria between gaseous and particulate phases. Several modifications to ISO 4387 Standard on aerosol collection were tested to improve the accuracy and reliability of aerosol capturing, with minimal deviation to the standard method. The proposed modifications are readily adoptable by laboratories already practicing the Standard for cigarette smoke analyses. Taking collectively with other available aerosol chemistry and biological results on HTPs in the literature, they show a fundamentally different aerosol in HTPs and call for category-specific product standards and terminology.

Teratogenic, bioenergetic, and behavioral effects of exposure to total particulate matter on early development of zebrafish (Danio rerio) are not mimicked by nicotine

Cigarette smoke has been associated with a number of pathologies; however, the mechanisms leading to developmental effects are yet to be fully understood. The zebrafish embryo is regarded as a 'bridge model'; however, not many studies examined its applicability to cigarette smoke toxicity. This study examined the effects of total particulate matter (TPM) from 3R4F reference cigarettes on the early development of zebrafish (Danio rerio). Zebrafish embryos were exposed to two concentrations of TPM (0.4 and 1.4 μg/mL equi-nicotine units) or nicotine at equivalent doses. The exposures began at 2h post-fertilization (hpf) and lasted until 96 hpf. Several physiological parameters were assessed during or after the exposure. We show that TPM increased mortality, delayed hatching, and increased the incidence of deformities in zebrafish. TPM exposure also increased the incidence of hemorrhage and disrupted the angiogenesis of the major vessels in the brain. Moreover, TPM exposure reduced the larval body length, decreased the heart rate, and reduced the metabolic rate. Biomarkers of xenobiotic metabolism and oxidative stress were also affected. TPM-exposed zebrafish also differed behaviorally: at 24 hpf the embryos had a higher frequency of spontaneous contractions and at 144 hpf the larvae displayed swimming hyperactivity. This study demonstrates that TPM disrupts several aspects of early development in zebrafish. The effects reported for TPM were not attributable to nicotine, since embryos treated with nicotine alone did not differ significantly from the control group. Collectively, our work illustrates the utility of zebrafish as an alternative model to evaluate the toxic effects of cigarette smoke constituents.

In vitro micronucleus assay for the analysis of total particulate matter in cigarette smoke: comparison of flow cytometry and laser scanning cytometry with microscopy

The possible genotoxicity of the total particulate matter (TPM) in cigarette smoke has typically been evaluated using the in vitro micronucleus assay. In recent years, automated scoring techniques have been developed to replace the manual counting process in this assay. However, these automated scoring techniques have not been applied in routine genotoxicity assays for the analysis of TPM to improve the assay efficiency. Chinese hamster ovary (CHO) cells were treated with TPM produced from 14 types of cigarettes at five concentrations (25-200μg/ml) without exogenous metabolic activation. The three following methods were used to score the micronucleus (MN) frequency: (a) flow cytometry with SYTOX and EMA dyes, which differentially stain micronuclei and apoptotic/necrotic chromatin to enhance assay reliability; (b) laser scanning cytometry with FITC and PI dyes, which is a system that combines the analytical capabilities of flow and image cytometry; and (c) visual microcopy with Giemsa dye. The test results obtained using the three methods were compared using correlation analysis. The key findings for this set of compounds include the following: (a) both flow cytometry- and laser scanning cytometry-based methods were effective for MN identification, (b) the three scoring methods could detect dose-dependent micronucleus formation for the 14 types of TPM, and (c) the MN frequencies that were measured in the same samples by flow cytometry, laser scanning cytometry, and visual microscopy were highly correlated, and there were no significant differences (p>0.05). In conclusion, both flow cytometry and laser scanning cytometry can be used to evaluate the MN frequency induced by TPM without exogenous metabolic activation. The simpler and faster processing and the high correlation of the results make these two automatic methods appropriate tools for use in in vitro micronucleus assays for the analysis of TPM using CHO cells.