Evaluation of the potentials of rice varieties and water management practices for reducing human health risks associated with polluted river water irrigated rice in Bangladesh.

The consumption of arsenic and trace-metal-contaminated rice is a human health concern worldwide, particularly in Bangladesh. In this study, the effects of rice varieties and water management practices on the concentrations of arsenic and trace metals in rice grains were investigated to reduce human health risks related to rice consumption. In addition, the performance of risk reduction using the optimum combination of rice variety and water management practices was quantitatively assessed using Monte Carlo simulation, in which non-carcinogenic and carcinogenic risk distributions under the status quo and the optimum combination were compared. The experimental results revealed that Dular and BRRI dhan45 (rice varieties) cultivated under alternate wetting and drying (AWD) and continuous flooding (CF) conditions showed the lowest hazard quotient (HQ) values for copper, cadmium, and arsenic and the lowest target cancer risk (TR) for arsenic. In Dular and BRRI dhan45 (AWD and CF) varieties, the proportion of the population for which HQs exceeded 1.0 (the reference value) tended to decrease (except for arsenic), compared with populations for which the rice varieties and water management practices were not specified. These results suggest that the use of optimum combinations of rice varieties and water management practices could reduce non-carcinogenic and carcinogenic risks associated with arsenic and trace metals uptake via rice grain consumption by the Bangladeshi people.

Determination of potential dermal exposure rates of phosphorus flame retardants via the direct contact with a car seat using artificial skin.

Dermal exposure to phosphorus flame retardants (PFRs) has received much attention as a major alternative exposure route in recent years. However, the information regarding dermal exposure via direct contact with a product is limited. In addition, in the commonly used dermal permeability test, the target substance is dissolved in a solvent, which is unrealistic. In this study, a dermal permeability test of PFRs in three car seats was performed using artificial skin. The PFR concentrations in the car seats are 0.12 wt% tris(2-chloroethyl) phosphate (TCEP), 0.030-0.25 wt% tris(2-chloroisopropyl) phosphate (TCPP), 0.15 wt% triphenyl phosphate (TPhP), 0.89 wt% cresyl diphenyl phosphate (CsDPhP), 0.074 wt% tricresyl phosphate (TCsP), and 0.46-4.7 wt% diethylene glycol bis [di (2-chloroisopropyl) phosphate (DEG-BDCIPP). The mean skin permeation rates for a contact time of 24 h are 14 (TCEP), 5.4-160 (TCPP), 0.67 (CsDPhP), 0.38 (TPhP), and 3.3-58 ng cm-2 h-1 (DEG-BDCIPP). The concentrations of TCsP in receptor liquid were lower than the limit of quantification at the contact time of 24 h. The skin permeation rates were significantly affected by the type of car seat (e.g., fabric or non-fabric). The potential dermal TCPP exposure rate for an adult via direct contact with the car seat during the average daily contact time (1.3 h), which was the highest value assessed in this study, was estimated to be 16,000 ng kg-1 day-1, which is higher than that related to inhalation and dust ingestion reported as significant exposure route of PFRs in previous studies. These facts reveal that dermal exposure associated with direct contact with the product might be an important exposure pathway for PFRs.

Development of a safety analysis method for volatile organic compounds using 2-phenoxyethanol as solvent.

Indoor volatile organic compounds (VOCs) are usually sampled using active carbon samplers and subsequently analyzed using gas chromatography-mass spectrometry (GC-MS) to assess the exposure risk to workers. Therefore, selection of a suitable solvent for VOC extraction is crucial. However, reports on the use of 2-phenoxyethanol-known for its low vapor pressure and low toxicity-as a solvent for extracting VOCs from activated carbon are lacking. Here, we show that 2-phenoxyethanol is a suitable alternative solvent with low toxicity and can extract a wide variety of VOCs without overlapping with target VOCs on the gas chromatogram. The recoveries of 2-phenoxyethanol were 57% (styrene) to 83% (methyl n-butyl ketone), which were higher than those of CS2, acetone, and n-hexane at room temperature. The recoveries improved to 67% (styrene) to 102% (isopentyl acetate) under 50 °C. Optimization of the GC conditions showed that a viscosity delay time of 3 s was required to avoid producing bubbles in the injection syringes. We selected DB-HeavyWAX as a column because it could be heated above the boiling point of 2-phenoxyethanol (247 °C), allowing the removal of 2-phenoxyethanol from the column. This study contributes to the development of analysis methods for VOCs under safe operating conditions.

Development of an analytical method for indoor polycyclic aromatic hydrocarbons and their halogenated derivatives by using thermal separation probe coupled to gas chromatography-tandem mass spectrometry.

Polycyclic aromatic hydrocarbons (PAHs) and their halogenated derivatives (XPAHs) have been a concern because of their high toxicity. Monitoring indoor PAHs and XPAHs concentrations is important for risk assessment because humans typically spend >90 % of their time indoors. However, the background levels of indoor PAHs and XPAHs concentrations are unknown because of the low sensitivity of conventional analytical methods. In this study, we developed a highly sensitive analytical method using a thermal separation probe (TSP) coupled to a gas chromatograph with a triple quadrupole mass spectrometer method for 26 PAHs and 40 XPAHs. The method quantification limit (MQL) values of the TSP method were 1.1 (3,8-dichlorofluoranthene)-906 (dibenzo[a,e]pyrene) times lower than those of the conventional method. The regression line comparing the TSP and conventional methods was y = (0.944 ± 0.0401)x, which was in good agreement. These results demonstrate that the TSP method can be applied to indoor air analysis. The total concentrations of PAHs and XPAHs were 944 and 73.5 pg m-3 for the house and 735 and 0.924 pg m-3 in the office, respectively. Among the detected compounds, 13 PAHs and XPAHs could not be detected using conventional methods because of their high MQL values. The composition of total toxicity equivalency values in the house was dominated by dibenzo[a,i]pyrene (DBaiP: 43.2 %) and dibenzo[a,h]pyrene (DBahP: 27.1 %), which could not be detected using the conventional method. Therefore, the TSP method can improve the risk assessment of indoor PAHs and XPAHs.

Enhancement of photodegradation of polyethylene with adsorbed polycyclic aromatic hydrocarbons under artificial sunlight irradiation.

The photodegradation of plastic waste produces microplastics (MPs) in marine environments. Plastics can adsorb hydrophobic organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) and can be transported over long distances. However, the impact of adsorbed pollutants on the photodegradation remains unknown. Here, we show that adsorbed PAHs act as photocatalysts that promote the photodegradation of polyethylene. Upon light irradiation, coloration and surface degradation of the PAH-adsorbed polyethylene sheets were observed, indicating that the PAH-adsorbed polyethylene sheets are less resistant to light. Furthermore, fluorene, phenanthrene, anthracene, benzo[a]anthracene, benzo[a]pyrene, and indeno[1,2,3-cd]perylene adsorbed on polyethylene MP exhibited lower photodegradation rates than the aqueous phase. These results indicate that these PAHs can act as photocatalysts; their role of PAHs may have two adverse effects on marine environment. First, enhanced photodegradation of plastic waste increased the production of MPs. Second, the lifetime of PAHs is extended, thereby enhancing PAHs pollution in marine environments.

Spatiotemporal distribution and pollution assessment of trace metals in the Buriganga River, Bangladesh.

The Buriganga River plays a key role in the socioeconomic structure of Dhaka, the capital of Bangladesh. However, this river is severely polluted and is considered one of the most polluted in the world. Therefore, this study aimed to assess the concentrations of various metals in the Buriganga River. A study was conducted from August 2019 to February 2020 to determine the concentrations of 16 metals in water samples (n = 210) collected from 10 distinct sites in the Buriganga River. The mean values for the concentrations of Cr, Mn, Ni, Zn, As, Se, Cd, Sb, and Pb in river water were above the guideline values prescribed by the WHO, Japan, and Bangladesh. Moreover, the fraction ratios of Be, Cr, Co, Ni, Cu, Zn, Se, Mo, Ag, Cd, Sb, and Pb were high (>0.85); consequently, these metals could accumulate at high concentrations in river sediments. Assessment using the single-factor pollution index allowed the classification of the pollution level as 'serious pollution' for Sb and 'heavy pollution' for Cd, Ni, and Pb. The trace metal concentrations in this river imply that crops cultivated along the river using river water may also be contaminated with trace metals.

Occurrence, potential source, and cancer risk of PM2.5-bound polycyclic aromatic hydrocarbons and their halogenated derivatives in Shizuoka, Japan, and Dhaka, Bangladesh.

Because of their unintentional formation and low vapor pressure, polycyclic aromatic hydrocarbons (PAHs) and their halogenated derivatives (XPAHs) in the atmosphere are distributed primarily to aerosolized particles with an aerodynamic diameter less than 2.5 µm (PM2.5). However, no information is available regarding the occurrence of PM2.5-bound PAHs and XPAHs in Bangladesh, one of the most highly PM2.5-polluted regions worldwide. In this study, we investigated the occurrence of PM2.5-bound PAHs and XPAHs in the atmospheres of Dhaka in Bangladesh and Shizuoka in Japan (as a reference) and estimated their incremental lifetime cancer risks (ILCRs). In addition, we statistically estimated the potential sources of PM2.5-bound PAHs and XPAHs by using principal component analysis and positive matrix factorization. The median concentration of total PM2.5-bound PAHs and XPAHs in Bangladesh was 24.2 times that in Japan. The estimated potential sources of PAHs clearly differed between Japan and Bangladesh, whereas those of XPAHs were largely (>80%) unknown in both countries. The median ILCR in Bangladesh was 2.81 × 10-3, which greatly exceeded the upper limit of acceptable risk (10-4). These results indicate that comprehensive monitoring and control of atmospheric PM2.5-bound PAHs and XPAHs are needed urgently, especially in highly polluted countries.

Accurate and ultrasensitive determination of 72 parent and halogenated polycyclic aromatic hydrocarbons in a variety of environmental samples via gas chromatography-triple quadrupole mass spectrometry.

Polycyclic aromatic hydrocarbons (PAHs) and their halogenated derivatives (XPAHs) are ubiquitous in various environmental media. Analytical problems, however, make it difficult to accurately determine their concentrations. To develop a satisfactory analytical method suitable for a diversity of PAHs and XPAHs in multiple environmental samples, we evaluated three commercial analytical columns (DB-5MS, Select PAH, and Rxi-PAH) for better chromatographic separation and optimized the analytical conditions for gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS). Comparison of the abilities of the columns to separate peaks revealed that the Rxi-PAH was the best column for both PAH and XPAH analyses. Optimization of analytical conditions for GC-MS/MS resulted in sensitivities for PAHs and XPAHs that were 4.2-fold-2600-fold higher than the sensitivities of GC-high-resolution MS (GC-HRMS) (an example of a traditional analytical method). Although there were no statistically significant differences between the instrumental detection limits (IDLs) of PAHs and XPAHs measured by GC-HRMS, the IDLs of XPAHs were significantly lower than those of PAHs when measured by GC-MS/MS. This difference could be attributed to the unique ionization patterns of XPAHs in the GC-MS/MS analysis, which suppressed background noise and increased the analytical sensitivity. Analyses of PAHs and XPAHs in grilled chicken, vehicle exhaust, sea sediment, ambient air, and indoor dust via the analytical method optimized in this study revealed that the proposed method was sufficiently sensitive, comprehensive, and versatile for risk assessment purposes, and could eliminate interferences associated with the co-elution of target PAHs and XPAHs.

Quantification of Brominated Polycyclic Aromatic Hydrocarbons in Environmental Samples by Liquid Chromatography Tandem Mass Spectrometry with Atmospheric Pressure Photoionization and Post-column Infusion of Dopant.

A sensitive method for the quantification of brominated polycyclic aromatic hydrocarbons (BrPAHs) in environmental samples is yet to be developed. Here, we optimized the analytical conditions for liquid chromatography tandem mass spectrometry with atmospheric pressure photoionization and post-column infusion of dopant (LC-DA-APPI-MS/MS). We then compared the sensitivity of our developed method with that of conventional gas chromatography high-resolution MS (GC-HRMS) by comparing the limits of quantification (LOQs) for a range of BrPAHs. Finally, to evaluate our developed method, 12 BrPAHs in sediments and fish collected from Tokyo Bay, Japan, were analyzed; 9 common PAHs were also targeted. The LOQs of the developed analytical method were 14 - 160 times lower than those of GC-HRMS for the targeted BrPAHs. The developed analytical method is a sensitive approach for determining the concentrations of BrPAHs in sediment and fish samples.

Risk assessment of polycyclic aromatic hydrocarbons and their chlorinated derivatives produced during cooking and released in exhaust gas.

Cooking exhaust gas includes polycyclic aromatic hydrocarbons (PAHs) that are unintentionally generated during cooking, which exposes the cook and others in the vicinity to these toxic compounds. However, information on the occurrence of PAHs, particularly their chlorinated derivatives (ClPAHs), in cooking exhaust gas is limited. Here, we determined the concentrations of 12 PAHs and 20 ClPAHs in cooking exhaust gas emitted during gas-grilling of a Pacific saury using a typical Japanese fish grill in an indoor kitchen. The total concentrations of PAHs and ClPAHs in the cooking exhaust gas were 3400 and 19 ng m-3, respectively. All 12 PAHs were detected in the cooking exhaust gas, with phenanthrene (2100 ng m-3), fluorene (630 ng m-3), and anthracene (200 ng m-3) detected at the highest concentrations. Four of the 20 ClPAHs were detected, with 9-monochlorinated phenanthrene detected at the highest concentration (12 ng m-3). The exposure rates for the cook to the PAHs and ClPAHs in the cooking exhaust gas, estimated using the National Institute of Advanced Industrial Science and Technology - Indoor Consumer Exposure Assessment Tool (AIST-ICET), were in the range of 7.2-72 ng-BaPeq kg-1 day-1 (toxic equivalent concentrations relative to the toxicity of benzo[a]pyrene), which was comparable with that for dietary ingestion of cooked foods (54 ng-BaPeq kg-1 day-1). A risk assessment of exposure to PAHs and ClPAHs in cooking exhaust gas in the indoor environment revealed that this gas may pose a health risk to the cook (incremental lifetime cancer risk: 2.1 × 10-6 to 2.1 × 10-5), indicating that further investigations are warranted.

Mitigation of the inhibitory effects of co-existing substances on the Fenton process by UV light irradiation.

Co-existing substances (substances not targeted for degradation) can negatively affect wastewater treatment process performance. Here, we quantitatively evaluated the effects of propanal, a common co-existing substance, on the degradation of the azo-dye Orange II, a common pollutant, by the Fenton process to provide data for the development of measures to reduce the effects of co-existing substances on this wastewater treatment process. Inhibition rate (IR; ratio of the reaction rate constants obtained in the absence and presence of propanal) was calculated to examine the effects of propanal on the degradation of Orange II. The IRs for the Fenton process in the first phase and the second phase were 1.6 and 4.2, respectively. However, addition of ultraviolet irradiation to the Fenton process (i.e., the photo-Fenton process) resulted in a comparable IR for the first phase but a markedly lower IR for the second phase. We attributed this to the improvement of the photo-reduction reaction rate due to complexation of propanal with ferric ions, which compensated for the scavenger effects (the trapping of OH radicals) of propanal. Thus, ultraviolet irradiation reduced the inhibitory effects of propanal on the degradation of Orange II by the Fenton process.

Probabilistic exposure assessment of aggregate rates of dermal exposure of Japanese women and children to parabens in personal care products.

Parabens (p-hydroxybenzoic acids) are commonly used as preservatives in personal care products. Although the rate of exposure to a single product may be small, it is possible for an individual to have marked exposure to parabens through the use of multiple personal care products (aggregate exposure). To assess the risks associated with aggregate exposure to parabens, we estimated the dermal exposure rate distributions of four major parabens (methylparaben, MP; ethylparaben, EP; propylparaben, PP; butylparaben, BP) in various products for women (>20 years old) and children (1-3 years old) by using the probabilistic exposure assessment tool ConsExpo. Integrated exposure rates were then calculated as the sum of exposure rates for individual products. Aggregate exposure rates for women were 1.2 (median) (0.13 [5%ile], 6.9 [95%ile]), 0.43 (0.029, 3.0), 0.35 (0.032, 1.9), and 0.25 (0.027, 1.2) mg kg-bw-1 day-1 for MP, EP, PP, and BP, respectively. Those for children were 0.47 (0.054, 2.2), 0.11 (0.012, 0.60), 0.13 (0.012, 0.78), and 0.13 (0.0065, 0.85) mg kg-bw-1 day-1 for MP, EP, PP, and BP, respectively. Integrated exposure rates for women were several times those for children. In both cases, personal care products that were applied to larger areas of skin and were used more frequently were more likely to be associated with higher exposure rates. According to the results of a risk assessment using a margin of exposure approach, aggregate rates of exposure to PP and BP, but not MP or EP, were high enough to warrant concern about disruption of the reproductive system.

Silica nanoparticles produced by explosive flash vaporization during earthquakes.

Hydrothermal activity in the crust results in the precipitation of large volumes of silica and often involves the formation of ore deposits, the shaping of geothermal systems, and recurring earthquakes. Pore fluid pressures fluctuate between lithostatic and hydrostatic, depending on seismic activity, and some models suggest the possibility of flash vaporization, given that fluid pressures can drop to the level of vapour at fault jogs during seismic slip. The phase changes of water could create extremely high supersaturations of silica, but the mechanisms of quartz vein formation under such extreme conditions remain unclear. Here we describe flash experiments conducted with silica-saturated solutions under conditions ranging from subcritical to supercritical. We found that amorphous silica is produced instantaneously as spherical nano- to micron-scale particles via nucleation and aggregation during the evaporation of water droplets. The nanoparticles are transformed to microcrystalline quartz very rapidly by dissolution and precipitation in hydrothermal solutions, with this process requiring less than one day under supercritical conditions because of the huge surface areas involved. We suggest that such short-lived silica nanoparticles have significant impacts on the dynamic changes in mechanical behaviour and hydrology of hydrothermal systems in volcanic areas.

Simultaneous determination of polycyclic aromatic hydrocarbons and their chlorinated derivatives in grilled foods.

Polycyclic aromatic hydrocarbons (PAHs) are unintentionally generated in foods that are cooked, and dietary ingestion of these PAHs is regarded as the dominant route of exposure to PAHs. Some chlorinated PAHs (ClPAHs) are more toxic than their corresponding parent PAHs and can also be generated in food during cooking. Knowledge of the concentrations of ClPAHs in cooked foods has been limited by the lack of an adequate analytical method for measuring ClPAH concentrations in cooked foods. In this study, we developed an analytical method for simultaneous determination of PAHs and ClPAHs in lipid-rich foods. The combination of a potassium hydroxide silica gel column and an activated carbon cartridge enabled us to simultaneously measure PAH and ClPAH concentrations in raw and grilled fish and meats. Twelve kinds of PAHs (e.g., fluorene [Fle], phenanthrene [Phe], fluoranthene [Flu], and pyrene [Pyr]) were detected in grilled foods. The concentrations ranged from below the limit of quantitation (

Dermal exposure to plasticizers in nail polishes: An alternative major exposure pathway of phosphorus-based compounds.

Phosphorus-based compounds are used as plasticizers in the manufacture of many products found in the indoor environment. Here we quantitatively investigated dermal exposure to phosphorus-based compounds contained in 45 nail polishes purchased in Japan. The alternative plasticizer triphenyl phosphate (TPhP) was detected in some samples of the nail polishes made in the USA (concentration, 1.1-1.8 wt%). The potential dermal exposure rates for TPhP, estimated using ConsExpo (version 5.0; Dutch National Institute for Public Health and the Environment), were in the range 200 (5%ile)-1700 (50%ile)-5000 (95%ile) ng kg-bw-1 day-1, which is more than 1400 times the reported values for exposure via dust ingestion and inhalation. Thus, dermal exposure via nail polish may be a major route of exposure to TPhP. The margin of exposure range for TPhP was 3.6 × 105-4.1 × 104-1.4 × 104. For comparison, the potential dermal exposure rate range for the conventional plasticizer dibutyl phthalate and the alternative plasticizer acetyl tributyl citrate was 360-3500-14,000 and 430-4100-17,000 ng kg-bw-1 day-1, respectively, and the margin of exposure range was 4.1 × 103-4.2 × 102-1.1 × 102 and 2.3 × 105-2.4 × 104-5.9 × 103, respectively.

Comparison of rates of direct and indirect migration of phosphorus flame retardants from flame-retardant-treated polyester curtains to indoor dust.

In this study, the pathways for migration of phosphorus flame retardants (PFRs), tris(1,3-dichloroisopropyl) phosphate (TDCPP) and tricresyl phosphate (TCsP) which were detected from curtains often, from flame-retardant-treated polyester curtains to indoor dust were investigated. Two possible migration pathways were compared quantitatively: (1) an indirect pathway in which the PFRs in the curtains first evaporate from the curtains and are then adsorbed onto indoor dust and (2) a direct pathway in which the PFRs are directly transferred to dust placed on the curtains. The contribution of the indirect pathway was evaluated by means of emission cell tests, which showed that the area-specific emission rates from curtains treated with PFRs were 0.044 (TDCPP, Curtain 5), 0.17 (TDCPP, Curtain 8), and 0.060 (TCsP, Curtain 12) µg m-2 h-1 at 20 °C (averaged during 24 h). The contribution of the direct pathway was evaluated by measurement of the time dependence of PFR concentrations on the indoor dust placed on the curtains. These measurements indicated that PFR concentrations on the dust increased with time and that the direct migration rates of PFRs from curtains treated with PFRs were 4.4 (TDCPP, Curtain 5), 12 (TDCPP, Curtain 8), and 7.0 (TCsP, Curtain 12) µg m-2 h-1 at 20 °C (averaged during 24 h), or 71-120 times the indirect migration rate. This result suggests that the direct pathway can be expected to predominate.

Effects of soil water content and elevated CO2 concentration on the monoterpene emission rate of Cryptomeria japonica.

Monoterpenes emitted from plants contribute to the formation of secondary pollution and affect the climate system. Monoterpene emission rates may be affected by environmental changes such as increasing CO2 concentration caused by fossil fuel burning and drought stress induced by climate change. We measured monoterpene emissions from Cryptomeria japonica clone saplings grown under different CO2 concentrations (control: ambient CO2 level, elevated CO2: 1000µmolmol-1). The saplings were planted in the ground and we did not artificially control the SWC. The relationship between the monoterpene emissions and naturally varying SWC was investigated. The dominant monoterpene was α-pinene, followed by sabinene. The monoterpene emission rates were exponentially correlated with temperature for all measurements and normalized (35°C) for each measurement day. The daily normalized monoterpene emission rates (Es0.10) were positively and linearly correlated with SWC under both control and elevated CO2 conditions (control: r2=0.55, elevated CO2: r2=0.89). The slope of the regression line of Es0.10 against SWC was significantly higher under elevated CO2 than under control conditions (ANCOVA: P<0.01), indicating that the effect of CO2 concentration on monoterpene emission rates differed by soil water status. The monoterpene emission rates estimated by considering temperature and SWC (Improved G93 algorithm) better agreed with the measured monoterpene emission rates, when compared with the emission rates estimated by considering temperature alone (G93 algorithm). Our results demonstrated that the combined effects of SWC and CO2 concentration are important for controlling the monoterpene emissions from C. japonica clone saplings. If these relationships can be applied to the other coniferous tree species, our results may be useful to improve accuracy of monoterpene emission estimates from the coniferous forests as affected by climate change in the present and foreseeable future.

Methods for the analysis of organophosphorus flame retardants-Comparison of GC-EI-MS, GC-NCI-MS, LC-ESI-MS/MS, and LC-APCI-MS/MS.

Organophosphorus flame retardants (PFRs) are extensively used as alternatives to banned polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCD). In this study, we analyzed 14 PFRs by means of four mass-spectrometry-based methods: gas chromatography combined with electron-impact mass spectrometry (GC-EI-MS) or negative-chemical-ionization mass spectrometry (GC-NCI-MS) and liquid chromatography combined with tandem mass spectrometry using electrospray ionization (LC-ESI-MS/MS) or atmospheric pressure chemical ionization (LC-APCI-MS/MS). The limits of quantification (LOQs) for LC-ESI-MS/MS and LC-APCI-MS/MS (0.81-970 pg) were 1-2 orders of magnitude lower than the LOQs for GC-EI-MS and GC-NCI-MS (2.3-3900 pg). LC-APCI-MS/MS showed the lowest LOQs (mean = 41 pg; median = 3.4 pg) for all but two of the PFRs targeted in this study. For LC-APCI-MS/MS, the lowest LOQ was observed for tributyl phosphate (TBP) (0.81 pg), and the highest was observed for tris(butoxyethyl) phosphate (TBOEP) (36 pg). The results of this study indicate that LC-APCI-MS/MS is the optimum analytical method for the target PFRs, at least in terms of LOQ.

Effects of characteristics of waste incinerator on emission rate of halogenated polycyclic aromatic hydrocarbon into environments.

We determined the concentrations of halogenated polycyclic aromatic hydrocarbons (XPAHs), some of which are carcinogenic and/or mutagenic compounds, in fly and bottom ashes and stack gas collected from waste incinerators in Japan. The dominant XPAHs in stack gas were consistent with those in the urban atmosphere. The dioxin-like toxic equivalent (TEQ) concentration ranges of the XPAHs in stack gas, fly ash, and bottom ash were 0.00497-20.5ng-TEQm-3, 0.0541-101ng-TEQg-1, and 0.000914-2.00ng-TEQg-1, respectively. The TEQ concentrations of the XPAHs targeted in this study were higher than those of polychlorinated dibenzo-p-dioxins/dibenzofurans and polychlorinated biphenyls reported in the literature. The annual amounts of XPAHs produced in the waste incinerators ranged from 25.1 to 881g. The mass balance of XPAHs in each waste incinerator was calculated to evaluate the emission rate of XPAHs from waste incinerators. Less than 6.7% of the XPAHs produced in the waste incinerators were emitted into the atmosphere from the facilities in which the flue gas was treated by using a combination of bag filter and activated carbon. In contrast, from the facility using a bag filter only, approximately 50% of the XPAHs produced were emitted into the atmosphere. Thus, the flue gas treatment process appears to be a key determinant of the emission rate of XPAHs produced during waste incineration.

Rate of hexabromocyclododecane decomposition and production of brominated polycyclic aromatic hydrocarbons during combustion in a pilot-scale incinerator.

Here, we examined the incineration of extruded polystyrene containing hexabromocyclododecane (HBCD) in a pilot-scale incinerator under various combustion temperatures (800-950°C) and flue gas residence times (2-8sec). Rates of HBCD decomposition ranged from 99.996% (800°C, 2sec) to 99.9999% (950°C, 8sec); the decomposition of HBCD, except during the initial stage of combustion (flue gas residence time<2sec), followed a pseudo-first-order kinetics model. An Arrhenius plot revealed that the activation energy and frequency factor of the decomposition of HBCD by combustion were 14.2kJ/mol and 1.69sec-1, respectively. During combustion, 11 brominated polycyclic aromatic hydrocarbons (BrPAHs) were detected as unintentional by-products. Of the 11 BrPAHs detected, 2-bromoanthracene and 1-bromopyrene were detected at the highest concentrations. The mutagenic and carcinogenic BrPAHs 1,5-dibromoanthracene and 1-bromopyrene were most frequently detected in the flue gases analyzed. The total concentration of BrPAHs exponentially increased (range, 87.8-2,040,000ng/m3) with increasing flue gas residence time. Results from a qualitative analysis using gas chromatography/high-resolution mass spectrometry suggest that bromofluorene and bromopyrene (or fluoranthene) congeners were also produced during the combustion.