Quantitative Analysis of Mixed Halogen Dioxins and Furans in Fire Debris Utilizing Atmospheric Pressure Ionization Gas Chromatography-Triple Quadrupole Mass Spectrometry

Breast Cancer-Related Chemical Exposures in Firefighters

To fill a research gap on firefighter exposures and breast cancer risk, and guide exposure reduction, we aimed to identify firefighter occupational exposures linked to breast cancer. We conducted a systematic search and review to identify firefighter chemical exposures and then identified the subset that was associated with breast cancer. To do this, we compared the firefighter exposures with chemicals that have been shown to increase breast cancer risk in epidemiological studies or increase mammary gland tumors in experimental toxicology studies. For each exposure, we assigned a strength of evidence for the association with firefighter occupation and for the association with breast cancer risk. We identified twelve chemicals or chemical groups that were both linked to breast cancer and were firefighter occupational exposures, including polycyclic aromatic hydrocarbons, volatile aromatics, per- and polyfluoroalkyl substances, persistent organohalogens, and halogenated organophosphate flame retardants. Many of these were found at elevated levels in firefighting environments and were statistically significantly higher in firefighters after firefighting or when compared to the general population. Common exposure sources included combustion byproducts, diesel fuel and exhaust, firefighting foams, and flame retardants. Our findings highlight breast-cancer-related chemical exposures in the firefighting profession to guide equitable worker's compensation policies and exposure reduction.

Framework of the Integrated Approach to Formation Mechanisms of Typical Combustion Byproducts─Polyhalogenated Dibenzo-p-dioxins/Dibenzofurans (PXDD/Fs)

Understanding the mechanisms through which persistent organic pollutants (POPs) form during combustion processes is critical for controlling emissions of POPs, but the mechanisms through which most POPs form are poorly understood. Polyhalogenated dibenzo-p-dioxins and dibenzofurans (PXDD/Fs) are typical toxic POPs, and the formation mechanisms of PXDD/Fs are better understood than the mechanisms through which other POPs form. In this study, a framework for identifying detailed PXDD/Fs formation mechanisms was developed and reviewed. The latest laboratory studies in which organic free radical intermediates of PXDD/Fs have been detected in situ and isotope labeling methods have been used to trace transformation pathways were reviewed. These studies provided direct evidence for PXDD/Fs formation pathways. Quantum chemical calculations were performed to determine the rationality of proposed PXDD/Fs formation pathways involving different elementary reactions. Many field studies have been performed, and the PXDD/Fs congener patterns found were compared with PXDD/Fs congener patterns obtained in laboratory simulation studies and theoretical studies to mutually verify the dominant PXDD/Fs formation mechanisms. The integrated method involving laboratory simulation studies, theoretical calculations, and field studies described and reviewed here can be used to clarify the mechanisms involved in PXDD/Fs formation. This review brings together information about PXDD/Fs formation mechanisms and provides a methodological framework for investigating PXDD/Fs and other POPs formation mechanisms during combustion processes, which will help in the development of strategies for controlling POPs emissions.

Analysis of Grape Volatiles Using Atmospheric Pressure Ionization Gas Chromatography Mass Spectrometry-Based Metabolomics

Analysis of volatile compounds in fruits and plants can be a challenging task as they present in a large amount with structural diversity and high aroma threshold, the information on molecular ion can be very useful for compound identification. Electron ionization gas-chromatography-mass spectrometry (EI-GC-MS) which is widely used for the analysis of plant volatiles has a certain limitation providing the limited capability to characterize novel metabolites in a complex biological matrix due to hard fragmentation level. Atmospheric pressure ionization using APGC source in combination with high-resolution time-of-flight mass spectrometry (TOF-MS) provides an excellent combination of GC with high-resolution mass spectrometry. The APGC-MS approach provides several advantages over the conventional EI and CI based GC-MS techniques in metabolomics studies due to highly reduced fragmentation, which preserves molecular ion, and accurate mass measurement by HRMS allows to deduce the elemental composition of the volatile compounds. Moreover, the use of MS^E mode provides spectral similarity to EI in high-energy mode which can be used for the further confirmation of metabolite identity. We describe an APGC-MS-based untargeted metabolomics approach with a case study of grape volatile compounds and the development of a spectral library for metabolite identification.

Nontargeted Screening Using Gas Chromatography-Atmospheric Pressure Ionization Mass Spectrometry: Recent Trends and Emerging Potential

Gas chromatography–high-resolution mass spectrometry (GC–HRMS) is a powerful nontargeted screening technique that promises to accelerate the identification of environmental pollutants. Currently, most GC–HRMS instruments are equipped with electron ionization (EI), but atmospheric pressure ionization (API) ion sources have attracted renewed interest because: (i) collisional cooling at atmospheric pressure minimizes fragmentation, resulting in an increased yield of molecular ions for elemental composition determination and improved detection limits; (ii) a wide range of sophisticated tandem (ion mobility) mass spectrometers can be easily adapted for operation with GC–API; and (iii) the conditions of an atmospheric pressure ion source can promote structure diagnostic ion–molecule reactions that are otherwise difficult to perform using conventional GC–MS instrumentation. This literature review addresses the merits of GC–API for nontargeted screening while summarizing recent applications using various GC–API techniques. One perceived drawback of GC–API is the paucity of spectral libraries that can be used to guide structure elucidation. Herein, novel data acquisition, deconvolution and spectral prediction tools will be reviewed. With continued development, it is anticipated that API may eventually supplant EI as the de facto GC–MS ion source used to identify unknowns.

Comprehensive two-dimensional gas chromatography thermodynamic modeling and selectivity evaluation for the separation of polychlorinated dibenzo-p-dioxins and dibenzofurans in fish tissue matrix

Comprehensive two-dimensional gas chromatography (GC×GC) is a powerful tool for complex separations. The selectivity and sensitivity benefits from thermally modulated GC×GC were applied to the analysis of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Thermodynamic indices of 50 PCDD/Fs, including the 17 toxic 2378-substituted congeners, were collected and used to model one-dimensional and two-dimensional separations with the Rtx-Dioxin2 and Rxi-17SilMS capillary GC columns. Thermodynamic modeling was used to determine the optimal conditions to take advantage of the selectivity differences between the Rxi-17SilMS and Rtx-Dioxin2 to separate all PCDD/Fs congeners from the 2378-substituted compounds by GC×GC. The modeled elution order patterns closely matched the experimental elution order in 40 of the 45 tetrachlorinated through hexchlorinated compounds analyzed. The heptachlorinated and octachlorinated congeners were not included in the elution order modeling as they are readily resolved from other dioxin congeners. The Rxi-17SilMS crossed with the Rtx-Dioxin2 was able to separate all 2378-substituted compounds in a single separation in a fish matrix. Thirty-three additional PCDD/F congeners were added to the fish matrix that coelute with the 2378-substituted congeners. The Rxi-17SilMS crossed with the Rtx-Dioxin2 was able to fully resolve 11 of the 2378-substituted congeners with the other six congeners exhibiting coelutions with only one other congener.

Quantitative and semiquantitative analyses of hexa-mix-chlorinated/brominated benzenes in fly ash, soil and air using gas chromatography-high resolution mass spectrometry assisted with isotopologue distribution computation

Hexa-mix-chlorinated/brominated benzenes (HXBs), a group of newly found analogues of hexachlorobenzene (HCB) and hexabromobenzene (HBB), may exhibit similar environmental risks and toxicities as HCB and HBB, and therefore possess high interests in environmental and toxicological research. Yet information regarding HXBs in the environment remains scarce. In this study, we developed an isotope dilution method for quantitative and semiquantitative determination of five HXBs in fly ash, soil and air using gas chromatography high resolution mass spectrometry (GC-HRMS) in multiple ion detection mode. The samples were Soxhlet-extracted and purified with multilayer composite silica gel-alumina columns, followed by GC-HRMS detection. Identification of HXBs was conducted by the comparison between theoretical and detected mass spectra using paired-samples T test and cosine similarity analysis. Two HXBs (C₆BrCl₅ and C₆Br₄Cl₂) with reference standards were quantitatively determined while the rest three (C₆Br₂Cl₄, C₆Br₃Cl₃ and C₆Br₅Cl) without reference standards were semiquantitatively analyzed by sharing the calibration curves of C₆BrCl₅ and C₆Br₄Cl₂ in cooperation with isotopologue distribution computation. The accuracies for C₆BrCl₅ and C₆Br₄Cl₂ were 87.3-107.8% with relative standard deviations (RSD) of 2.8-5.0%. The method limits of quantification of the HXBs were 0.10 ng/g in fly ash and soil samples and 0.09 pg/m³ in ambient air samples. The recoveries ranged from 42.7% to 102.1% with RSD of 3.7-13.9%. This method has been successfully applied to the analysis of the HXBs in the environmental samples. The total concentrations of HXBs in the fly ash, soil and ambient air samples were 19.48 ng/g, 10.44 ng/g and 5.13 pg/m³, respectively, which accounted for 10.6%, 0.4% and 10.8% of the corresponding total concentrations of HCB and HBB. This study provides a reference method for quantitative and/or semiquantitative analyses of novel mix-halogenated organic compounds, and sheds light on the full picture of HXBs pollution in the environment.

Background levels of dioxin-like polychlorinated biphenyls (dlPCBs), polychlorinated, polybrominated and mixed halogenated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs, PBDD/Fs & PXDD/Fs) in sera of pregnant women in Accra, Ghana

Human exposure data on dioxins and dioxin-like compounds (DLCs) in Ghana are limited. Based on health risks associated with dioxins and DLCs, the impact of maternal body burdens on foetal exposure is significant. This is the first study that assesses polychlorinated, polybrominated and mixed halogenated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs, PBDD/Fs and PXDD/Fs), and dioxin-like polychlorinated biphenyls (dlPCBs) in sera of primiparous Ghanaians. Our sample selection includes 34 participants from two municipalities (Accra and Tema), and explores contributions from environmental and dietary exposures using questionnaire data. Sample preparation involved C₁₈ solid phase extraction, purification with acidified silica and lipid removal cartridges, and detection with gas chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry. The calculated average toxic equivalent concentration was 5.3 pg TEQ/g lw, with contributions from dlPCBs (1.25 pg TEQ/g lw), PCDD/Fs (3.10 pg TEQ/g lw), PBDD/Fs (0.49 pg TEQ/g lw) and PXDD/Fs (0.50 pg TEQ/g lw). The calculated total TEQ concentration was lower than background TEQ concentrations reported in sera of pregnant women globally. Positive correlations were obtained for total dioxins and DLC concentrations with age and Body Mass Index (BMI). Dietary intake of seafood and dairy products had a strong influence on PCDD/F and dlPCB concentrations. Statistically significant differences were observed for dioxins and DLCs in participants from Accra (in close proximity to Agbogbloshie e-waste site) and Tema. Given the significant TEQ contribution of PBDD/Fs and PXDD/Fs (~20%), it is essential to explore these classes of dioxins and DLCs in future biomonitoring studies as they may pose health risks, and add extra diagnostic information in source exposure investigations.

Non-targeted GC/MS analysis of exhaled breath samples: Exploring human biomarkers of exogenous exposure and endogenous response from professional firefighting activity

A non-targeted analysis workflow was applied to analyze exhaled breath samples collected from firefighters pre- and post-structural fire suppression. Breath samples from firefighters functioning in attack and search positions were examined for target and non-target compounds in automated thermal desorption-GC/MS (ATD-GC/MS) selected ion monitoring (SIM)/scan mode and reviewed for prominent chemicals. Targeted chemicals included products of combustion such as benzene, toluene, xylenes, and polycyclic aromatic hydrocarbons (PAH) that serve as a standard assessment of exposure. Sixty unique chemical features representative of exogenous chemicals and endogenous compounds, including single-ring aromatics, polynuclear aromatic hydrocarbons, volatile sulfur-containing compounds, aldehydes, alkanes, and alkenes were identified using the non-targeted analysis workflow. Fifty-seven out of 60 non-targeted features changed by at least 50% from pre- to post-fire suppression activity in at least one subject, and 7 non-targeted features were found to exhibit significantly increased or decreased concentrations for all subjects as a group. This study is important for (1) alerting the firefighter community to potential new exposures, (2) expanding the current targeted list of toxicants, and (3) finding biomarkers of response to firefighting activity as reflected by changes in endogenous compounds. Data demonstrate that there are non-targeted compounds in firefighters' breath that are indicative of environmental exposure despite the use of protective gear, and this information may be further utilized to improve the effectiveness of personal protective equipment.

Fast gas chromatography-atmospheric pressure (photo)ionization mass spectrometry of polybrominated diphenylether flame retardants

Gas chromatography (GC) and mass spectrometry (MS) are powerful, complementary techniques for the analysis of environmental toxicants. Currently, most GC-MS instruments employ electron ionization under vacuum, but the concept of coupling GC to atmospheric pressure ionization (API) is attracting revitalized interest. API conditions are inherently compatible with a wide range of ionization techniques as well high carrier gas flows that enable fast GC separations. This study reports on the application of atmospheric pressure chemical ionization (APCI) and a custom-built photoionization (APPI) source for the GC-MS analysis of polybrominated diphenyl ethers (PBDEs), a ubiquitous class of flame retardants. Photoionization of PBDEs resulted in the abundant formation of molecular ions M^•+ with very little fragmentation. Some photo-oxidation was observed, which differentiated critical BDE isomers. Formation of protonated molecules [M+H]⁺ did not occur in GC-APPI because the ionization energy of H₂O (clusters) exceeds the energy of the ionizing photons. Avoiding mixed-mode ionization is a major advantage of APPI over APCI, which requires careful control of the source conditions. A fast GC-API-MS method was developed using helium and nitrogen carrier gases that provides good separation of critical isomers (BDE-49/71) and elution of BDE 209 in less than 7 min (with He) and 15 min (with N₂). It will be shown that the GC-APPI and GC-APCI methods match the sensitivity and improve upon the selectivity and throughput of established methods for the analysis of PBDEs using standard reference materials (NIST SRM 1944 and SRM 2585) and selected environmental samples.

Determination of polybrominated diphenyl ethers and novel brominated flame retardants in human serum by gas chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry

The accurate detection of brominated flame retardants (BFRs) in humans is an area of high scientific interest and regulatory need due to their potential toxicity. The instrumental analysis of BFRs was commonly performed on gas chromatography-mass spectrometry (GC-MS) operating in electron ionization (EI) or negative chemical ionization (NCI) modes. However, soft ionization techniques, such as atmospheric pressure chemical ionization (APCI), may be more suitable for the analysis of BFRs because the BFRs show high fragmentation in EI and low selectivity in NCI. Additionally, accurate quantifications of BFRs in complex matrices is challenging due to their low concentrations and therefore, a highly sensitive technique is desperately needed. In this study, a new methodology based on gas chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry (GC-APCI-MS/MS) analysis was developed for the determination of thirteen BFRs (eight usually monitored polybrominated diphenyl ethers (PBDEs) congeners and five additional novel BFRs) in human serum. The primary task was to evaluate the potential of the GC-APCI-MS/MS technique for the trace analysis of BFRs in human serum. The results of the spiked recovery test using fetal bovine serum showed that mean recoveries of the analytes ranged from 83.4% to 118% with reduced swing differential signaling (RSDs) of ≤21.1%. The methodological limits of detection (mLOD) of the analytes ranged from 0.04 to 30 pg/mL, and these values were at least one order of magnitude lower than those estimated by the authors in a previous study using GC-NCI-MS or GC-EI-MS/MS, indicating that GC-APCI-MS/MS is more sensitive. Specially, compared to GC-NCI-MS and GC-EI-MS/MS, when GC-APCI-MS/MS was used for the detection of highly brominated BFRs, such as BDE-209 and decabromodiphenyl ethane (DBDPE), a notable improvement in sensitivity and reliability was obtained using a deactivated capillary column connected to the analytical column as the transfer line and maintaining a high temperature to improve the chromatographic behaviors. The developed methodology was successfully used for the analysis of BFRs in human serum collected from residents living in a BFR production area and Beijing.

Evaluation of multiple alternative instrument platforms for targeted and non-targeted dioxin and furan analysis

The use of gas chromatography coupled to high-resolution magnetic sector mass spectrometers (GC-HRMS) is well established for dioxin and furan analysis. However, the use of gas chromatography coupled to triple quadrupole (MS/MS) and time of flight (TOF) mass spectrometers with atmospheric pressure ionization (API) and traditional electron ionization (EI) for dioxin and furan analysis is emerging as a viable alternative to GC-HRMS screening. These instruments offer greater versatility in the lab for a wider range of compound identification and quantification as well as improved ease of operation. The instruments utilized in this study included 2 API-MS/MS, 1 traditional EI-MS/MS, an API-quadrupole time of flight mass spectrometer (API-QTOF), and a EI-high-resolution TOF (EI-HRTOF). This study compared these 5 instruments to a GC-HRMS using method detection limit (MDLs) samples for dioxin and furan analysis. Each instrument demonstrated acceptable MDL values for the 17 chlorinated dioxin and furans studied. The API-MS/MS instruments provide the greatest overall improvement in MDL value over the GC-HRMS with a 1.5 to 2-fold improvement. The API-QTOF and EI-TOF demonstrate slight increases in MDL value as compared with the GC-HRMS with a 1.5-fold increase. The 5 instruments studied all demonstrate acceptable MDL values with no MDL for a single congener greater than 5 times that for the GC-HRMS. All 5 instruments offer a viable alternative to GC-HRMS for the analysis of dioxins and furans and should be considered when developing new validated methodologies.

Occurrence of brominated dioxins in a study using various firefighting methods

The use of different firefighting methods influences how fast a fire is extinguished and how fast the temperature drops in the area affected by the fire. These differences may also influence the formation of harmful pollutants during firefighting of an accidental fire. The aim was to study occurrence of brominated dibenzo-p-dioxins and furans (PBDD/Fs) in gas and soot during five fire scenarios resembling a small apartment fire and where different firefighting methods were used. Samples of gas and soot were taken both during the buildup of the fire and during the subsequent extinguishing of the fire while using different firefighting methods (nozzle, compressed air foam system, cutting extinguisher) and an extinguishing additive. New containers equipped with identical sets of combustible material were used for the five tests. The use of different firefighting methods and extinguishing additive induced variations in concentration and congener profiles of detected PBDD/Fs. The concentration range of ∑PBDD/Fs in gas was 4020-18,700pg/m³, and in soot 76-4092pg/m². PBDFs were the predominant congeners and 1,2,3,4,6,7,8-HpBDF was the most abundant congener. Chlorinated dibenzo-p-dioxins and furans (PCDD/Fs) were also monitored. The PBDD/Fs contributed with in average 97% to the total (PCDD/Fs plus PBDD/Fs) toxic equivalents, in soot and gas. During extinguishing, the shorter time the temperature was around 300°C, the lower occurrence of PBDD/Fs. In the study the firefighting methods showed a difference in how effectively they induced a temperature decrease below 300°C in the fire zone during quenching, where cutting extinguishing using additive and the compressed air foam system showed the fastest drop in temperature.