Toxicological evidence integration to confirm the biological plausibility of the association between humidifier disinfectant exposure and respiratory diseases using the AEP-AOP framework.

Objectives: Exposure to humidifier disinfectants has been linked to respiratory diseases, including interstitial lung disease, asthma, and pneumonia. Consequently, numerous toxicological studies have explored respiratory damage as both a necessary and sufficient condition for these diseases. We systematically reviewed and integrated evidence from toxicological studies by applying the evidence integration method established in previous research to confirm the biological plausibility of the association between exposure and disease. Methods: We conducted a literature search focusing on polyhexamethylene guanidine phosphate (PHMG) and chloromethylisothiazolinone/methylisothiazolinone (CMIT/MIT), the primary ingredients in humidifier disinfectants. We selected relevant studies based on their quality and the population, exposure, comparator, outcome (PECO) statements. These studies were categorized into 3 lines of evidence: hazard information, animal studies, and mechanistic studies. Based on a systematic review, we integrated the evidence to develop an aggregate exposure pathway-adverse outcome pathway (AEP-AOP) model for respiratory damage. The reliability and relevance of our findings were assessed by comparing them with the hypothesized pathogenic mechanisms of respiratory diseases. Results: The integration of each AEP-AOP component for PHMG and CMIT/MIT led to the development of an AEP-AOP model, wherein disinfectants released from humidifiers in aerosol or gaseous form reached target sites, causing respiratory damage through molecular initiating events and key events. The model demonstrated high reliability and relevance to the pathogenesis of respiratory diseases. Conclusion: The AEP-AOP model developed in this study provides strong evidence that exposure to humidifier disinfectants causes respiratory diseases. This model demonstrates the pathways leading to respiratory damage, a hallmark of these conditions.

Innovative approach to reveal source contribution of dissolved organic matter in a complex river watershed using end-member mixing analysis based on spectroscopic proxies and multi-isotopes.

Dissolved organic matter (DOM) in river watersheds dynamically changes based on its source during a monsoon period with storm event. However, the variations in DOM in urban and rural river watersheds that are dominated by point and non-point sources have not been adequately explored to date. We developed an innovative approach to reveal DOM sources in complex river watershed systems during pre-monsoon, monsoon, and post-monsoon periods using end-member mixing analysis (EMMA) by combining multi-isotope values (δ13C-DOC, δ15N-NO3 and δ18O-NO3) and spectroscopic indices (fluorescence index [FI], biological index [BIX], humification index [HIX], and specific UV absorbance [SUVA]). Several potential end-members of DOM sources were collected from watersheds, including top-soils, groundwater, plant group (fallen leaves, riparian plants, suspended algae), and different effluents (cattle and pig livestock, agricultural land, urban, industry facility, swine treatment facility and wastewater treatment facility). Concentrations of dissolved organic carbon, dissolved organic nitrogen, NO3-N, and NH4-N increased during the monsoon period with an increase in the input of anthropogenic DOM, which have higher HIX values owing to the flushing effect. The results of EMMA indicate that soil and agricultural effluents accounted for a substantial contribution of anthropogenic DOM at varying rates based on seasons. We also found that results of EMMA based on combining spectroscopic indices and δ13C-DOC isotope values were more accurate in tracing DOM sources with respect to land-use characteristics compared to applying only spectroscopic indices. The positive relationship between FI, BIX and δ15N-NO3 were revealed that nitrate would be decomposed from DOM affected by intensive agricultural activities. In addition, consistent with the EMMA results, the molecular composition of the DOM was clearly evidenced by a large number of CHON formulas, accounting for over 50% of the total characterized compounds, including pesticides and pharmaceuticals used in agriculture farmland and livestock. Our results clearly demonstrated that EMMA based on combing multi-stable isotopes and spectroscopic indices could be trace the DOM source, which is important for understanding changes in the DOM quality, and application of nitrate isotopes and molecular analysis supports in-depth interpretation. This study provides easy and intuitive techniques for the estimation of the relative impacts of DOM sources in complex river watersheds, which can be verified in various ways rather than relying on a single technique approach.

Hazardous characteristics of dust waste from metal manufacturing industries in South Korea.

The Ministry of Environment, South Korea, is involved in efforts to reduce safety-related accidents that could occur during hazardous waste disposal and minimise the environmental impacts of waste disposal. To reach such goals, new factors have been added that contribute to the hazardous characteristics of hazardous waste. The Ministry is also expanding regulations on inorganic and organic components present in hazardous waste for these factors and continues to correct the classification system to establish standards for waste components. Metallic dust, for example, is mostly generated during the operation of melting furnaces or precipitators and dangerous materials contained in this dust may cause accidents, such as explosions or fires. South Korean accident cases have confirmed that waste containing hazardous materials, such as Mg, Al and Mg-Al alloys, can cause such events. Therefore, this study analysed 28 dust samples collected from the dust accumulated in precipitators in 28 metal manufacturing facilities in South Korea. Nine samples were flammable and four samples were reactive to water. Two samples also exhibited leaching toxicities. The results applied to relevant laws in South Korea showed that the proportion of waste containing hazardous characteristics increased from 7.14% in the previous management category to 39.29% in the extended category, an overall increase of 32.15 percentage points.

Analysis of incombustibles in the feedstock to incineration facilities in South Korea for optimum sorting and management.

Korea's Ministry of Environment has implemented the Framework Act on Resource Recirculation to activate waste resource recovery. However, industrial waste treatment facilities have some problems related to diversity of waste received for proper management of wastes. Waste incineration facilities are required to receive and process combustible waste and are forbidden to re-consign waste to other waste treatment facilities without any processing. In reality, a large amount of incombustibles is injected into the incinerator because it is impossible to completely separate the incombustible materials. Therefore, it is necessary to develop additional management criteria for optimal operation of the incineration facility. This study was conducted to improve institutional management of incineration facilities in Korea. Through a literature review and statistics study, incombustible waste management trends were investigated. The characteristics of waste entering incineration facilities were surveyed. Physical composition and proximate analysis of incoming waste were conducted, and properties of the incombustibles mixed in feedstocks to waste incineration facilities were examined. As a result of this study, incombustibles mainly consisting of the construction and demolition waste, such as soil, glass, and metals, should be separated from feed sent to incinerators. A mechanical screening technique that sorts particles of 30-40 mm in size can be used to separate the incombustibles. Also, management criteria could be proposed to sort and re-consign the incombustibles.

Measurement and analysis of biomass content using gas emissions from solid refuse fuel incineration.

In this study, we compared the results of biomass and biocarbon content analysis of Solid Refuse Fuels using 14C method and selective dissolution method. Solid Refuse fuel Samples for biomass and biocarbon contents analysis were each collected from the silos and stack of the respective three facilities. Samples collected for 1, 10, 20, and 30 days for each method were analyzed. The analysis data were grouped into sample period, type and method and the optimum method for the detection of the biomass and biocarbon content was estimated. The biomass and biocarbon content showed a partially normal distribution. However, it does not satisfy equal variance. Therefore, we applied the parametric statistics Welch's ANOVA test and the nonparametric statistics Kruskal-Wallis test to compare the means of each sample group. The results of the Kruskal-Wallis test showed that sapmles collected over 20 days at Facility A had the same mean value. Therefore, when analyzing biocarbon content using the 14C method, conducting analyses by collecting exhaust gases for more than 20 days reduces errors in the results.

Analysis of incombustibles in the feedstock to incineration facilities in Republic of Korea for optimum sorting and management.

The Ministry of Environment, Republic of Korea has implemented the "Framework Act on Resource Recirculation" to activate waste resource recovery. However, industrial waste treatment facilities have some problems related to diversity of waste received for proper management of wastes. Waste incineration facilities are required to receive and process combustible waste and are forbidden to re-consign waste to other waste treatment facilities without any processing. In reality, a large quantity of incombustibles is injected into the incinerator because it is impossible to completely separate the incombustible materials. Therefore, it is necessary to develop additional management criteria for optimal operation of the incineration facility. This study was conducted to improve institutional management of incineration facilities in Korea. Through a literature review and statistics study, incombustible waste management trends were investigated. The characteristics of waste entering incineration facilities were surveyed. Physical composition and proximate analysis of incoming waste were conducted, and properties of the incombustibles mixed in feedstock to waste incineration facilities were examined. As a result of this study, incombustibles mainly consisting of the construction and demolition waste, such as soil, glass, and metals should be separated from feed sent to incinerators. A mechanical screening technique that sorts particles of 30-40 mm in size can be used to separate the incombustibles. Also, management criteria could be proposed to sort and re-consign the incombustibles.

Assessment of quality test methods for solid recovered fuel in South Korea.

Management of solid recovered fuel (SRF) in South Korea is unique from most other countries in that it is based on a single standard. All SRFs are distributed at the same price irrespective of their performance, resulting in utilization problems and a low degree of acceptance among consumers. Moreover, the difficulty of temperature maintenance during transportation, excessive ash content, and the use of inappropriate microwave acid digestion methods pose challenges to SRF reliability. To address these issues, we compared the relevant management statuses in South Korea with those of the international community and reviewed the effects of the transportation temperature, ash content, and microwave acid digestion technique. The moisture, ash, sulfur, and chlorine contents as well as the lower heating values (LHVs) of all the samples from South Korea were found to be below the standard [international] thresholds, and they were barely influenced by the transportation temperature. In addition, 5 g samples were found to be more appropriate for ash content analysis than the 20 g samples used in South Korea, with the former producing smaller standard deviations. The optimal microwave acid digestion conditions were also determined to be a reaction time with nitric acid of >10 min, temperature of 180 °C, and microwave power of 600 W. The results of this study highlight the need for revising the SRF test methods used in South Korea, to boost the market and enhance quality reliability.

Strategic environmental assessment for effective waste management in Korea: A review of the new policy framework.

This study examines the new policy framework, which includes effective environmental assessment procedure to manage waste in Korea. Concept of this framework pursues the important strategies toward the waste reduction, preservation of landfill area, stabilization and removal of hazardous substance in wastes, and optimal treatment for energy and material recovery from wastes. Therefore, it has begun on three points. First, activating the effective recycling system to reuse wastes will be essential to waste reduction. Second, the utilization of substitute resource can be expected through the optimal transforming the wastes into the recycled product, raw material, thermal energy, etc. Third, the characteristics of waste must be evaluated by strategic environmental assessment. To realize this concept, the strategic environment assessment with reinforcement of hazardous property, categorization of recycling type, and classification of environmental assessment procedure depending on the recycling type was provided. In addition, based on this environment assessment, the new policy framework was built through the established and revised Wastes Control Act by focusing on simple systematic procedure for decision of the possible recycling and strengthening the safety of the wastes to a higher level with promoting recycling activities.

Characteristics of PCDDs/PCDFs in stack gas from medical waste incinerators.

Toxic polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in 45 stack gas samples were measured from 19 medical waste incinerators in South Korea using high-resolution gas chromatography equipped with a high-resolution mass spectrometer. The average concentrations of the sum of 17 toxic PCDD/PCDF congeners emitted from the medical waste incinerators ranged from 0.153 to 101.9 ng/Sm3. Based on the World Health Organization toxic equivalency factor, they ranged from 0.007 to 5.437 ng-TEQ/Sm3. The congener patterns of PCDDs/PCDFs were described using principal component analysis and presented four patterns. In the evaluation of annual average total TEQ concentrations, outlying stack gas samples were excluded. In this study, the number of chlorine substitutions was evaluated as an important factor in congener patterns. Coefficient of determination values were employed for evaluation of correlation between PCDDs and PCDFs. 1,2,3,4,6,7,8-HpCDF was measured as the most emitted congener, while 2,3,4,7,8-PeCDF was the greatest TEQ contributor.

Determination and characterization of pharmaceuticals in sludge from municipal and livestock wastewater treatment plants.

This study investigated 24 pharmaceuticals compounds belonging to the classes of analgesics, stimulants, anti-seizures, non-steroidal anti-inflammatory drugs (NSAIDs), and antibiotics in the sludge of 12 municipal sewage treatment plants (S-sludge) and 4 livestock wastewater treatment plants (L-sludge) located across Korea. Over 70% of the target compounds were detected in at least one sample of S-sludge and L-sludge. The total concentration of the target pharmaceutical compounds detected in S-sludge was 2.622-422.8 mg kg-1and the most dominant compound was acetylsalicylic acid (ASA: 0.374-367.0 mg kg-1) whereas in L-sludge, the total concentration was 43.87-156.8 mg kg-1and the most abundant compound was oxytetracycline (OTC: 34.54-86.39 mg kg-1). Cluster analysis revealed two distinct groups: group A, which were S-sludge samples including ASA, carbamazepine (CBM), and others, and group B were L-sludge samples, dominated by antibiotics (CTC, OTC, LIN). The total daily load amount of the target pharmaceuticals in S-sludge was 0.010-268.9 kg day-1 while the L-sludge was 0.021-0.529 kg day-1. The estimated amounts of the target pharmaceutical discharged from S-sludge and L-sludge into the Korean environment were 150.2 ± 47.94 ton yr-1 and 15.05 ± 5.671 ton yr-1 respectively, but the discharged amount of antibiotics from S-sludge (6.945 ton yr-1) was lower than that from L-sludge (9.234 ton yr-1).

Static and dynamic flow analysis of PBDEs in plastics from used and end-of-life TVs and computer monitors by life cycle in Korea.

This study focused on a quantitative substance flow analysis (SFA) of polybrominated diphenyl ethers (PBDEs) in plastics from obsolete TVs and computer monitors that often contain large amounts of the flame retardants. According to the results of the static SFA study, 1.87 tons and 0.28 tons of PBDEs from newly manufactured TVs and computer monitors were introduced into households in 2011 in Korea, respectively. There were approximately 924 tons and 90.3 tons of PBDEs present in TVs and computer monitors in households during product use, respectively. The results of the dynamic SFA study indicated that in 2017 the amount of PBDEs from TVs and computer monitors in the recycling stage is expected to be 2.63 tons and 0.1 tons, respectively. Large fractions of PBDEs from used TVs are present in recycled plastics, while PBDE-containing computer monitors are exported to Southeast Asian countries. This research indicates that PBDEs were emitted the most from recycled plastic pellet processes upon recycling. Further study may be warranted to focus the flow of PBDEs in recycled plastic products in order to determine the final destination and disposal of these chemicals in the environment.

Emission of polybrominated diphenyl ethers (PBDEs) in use of electric/electronic equipment and recycling of e-waste in Korea.

The emission rates of polybrominated diphenyl ethers (PBDEs) from electric/electronic products during their use and disposal were estimated. E-wastes, including televisions and refrigerators, gathered at recycling centers were also analyzed to estimate their emissions. The average concentrations of PBDEs in TV rear covers produced before and after the year 2000 were 145,027 mg/kg and 14,049 mg/kg, respectively. The PBDEs concentration in TV front covers was lower than the concentration in TV rear covers. The concentration in the components of the refrigerator samples ranged from ND to 445 mg/kg. We estimated the atmospheric emissions of PBDEs based on the concentrations. The annual emissions from TV rear covers produced before 2000 were calculated to be approximately 162.1 kg and after 2000, the annual emissions were 18.7 kg. Refrigerators showed the lowest annual emissions of PBDEs (0.7 kg). The atmospheric concentrations were also measured to calculate emissions generated during the recycling process. The highest concentration was 16.86 ng/m(3) emitted from the TV sets during the dismantling process. The concentrations of PBDEs generated in the plastic processing field ranged from 2.05 to 5.43 ng/m(3) depending on the products, and ambient air in open-air yards showed concentrations in the range of 0.32 to 5.55 ng/m(3). Emission factors for the recycling process were calculated using the observed concentrations. The estimated emissions according to the emission factors ranged from 0.3×10(-1) to 90.3 kg/year for open-air yards and from 0.1×10(-1) to 292.7 kg/year for the dismantling and crushing processes of TV set, depending on the production year.

Assessment of fates of estrogens in wastewater and sludge from various types of wastewater treatment plants.

We measured five estrogens in the wastewater samples from the municipal wastewater treatment plants (M-WWTPs), livestock wastewater treatment plants (L-WWTPs), hospital WWTPs (H-WWTPs) and pharmaceutical manufacture WWTPs (P-WWTPs) in Korea. The L-WWTPs showed the highest total concentration (0.195-10.4 µg L(-1)) of estrogens in the influents, followed by the M-WWTPs (0.028-1.15 µg L(-1)), H-WWTPs (0.068-0.130 µg L(-1)) and P-WWTPs (0.015-0.070 µg L(-1)). Like the influents, the L-WWTPs (0.003-0.729 µg L(-1)) and the M-WWTPs (0.001-0.299µgL(-1)) also showed higher total concentration of estrogens in the effluents than the H-WWTPs (0.002-0.021 µg L(-1)) and P-WWTPs (0.011 µg L(-1) in one sample). The L-WWTPs (37.5-543 µg kg(-1), dry weight) showed higher total concentrations in sludge than the M-WWTPs (3.16-444 µg kg(-1), dry weight) like the wastewater. The distribution of estrogens in the WWTPs may be affected by their metabolism in the human body, their transition through biological treatment processes, and their usage for livestock growth. Unlike the concentration results, the daily loads of estrogens from the M-WWTPs were the highest, which is related to the high capacities of WWTPs.

Occurrence and distribution of pharmaceuticals in wastewater from households, livestock farms, hospitals and pharmaceutical manufactures.

Twenty-four pharmaceuticals were measured in wastewater from 12 municipal wastewater treatment plants (M-WWTPs), four livestock WWTPs (L-WWTPs), four hospital WWTPs (H-WWTPs) and four pharmaceutical manufacture WWTPs (P-WWTPs). The total concentration of pharmaceuticals in the influent samples was highest in the L-WWTPs followed by the P-WWTPs, H-WWTPs and M-WWTPs. The effluents had different patterns of pharmaceuticals than their corresponding influents because of the different fate of each compound in the WWTPs. Non-steroidal anti-inflammatory drugs (NSAIDs) were the most dominant in the influents from the M-WWTPs and P-WWTPs, while antibiotics were dominantly detected in the L-WWTP. In the H-WWTP influents, NSAIDs, caffeine and carbamazepine were dominant. In the P-WWTPs, the distribution of pharmaceuticals in the effluents varied with sampling sites and periods. The M-WWTP influents had the highest daily loads, while the effluents showed somewhat similar levels in all source types.

Characteristics and emission factors of PCDD/Fs in various industrial wastes in South Korea.

Since South Korea ratified Stockholm Convention in January 2007, there is an obligation to survey the national emission of PCDD/Fs through environmental routes other than the air for taking actions to reduce and/or eliminate the release of PCDD/Fs. In this study, PCDD/F-containing wastes from various industrial emission sources in Korea (n=388) except from incinerators were investigated to elucidate the emission characteristics and their emission factors of PCDD/Fs in each industry. The concentrations of PCDD/Fs in waste samples ranged ND-96,200 ng I-TEQ kg(-1) (or 66,600 ng WHO-TEQ kg(-1)) for solid phase samples and ND-11,100 pg I-TEQL(-1) (or 6800 ng WHO-TEQ L) for liquid samples, respectively. Elevated levels of PCDD/F concentrations and emission factors were found in the wastes from productions of Cu, Al, Zn, Iron/steel, Pb, EDC/VCM/PVC and from waste landfill sites. The wastes from productions of cement (kilns) and acetylene (carbide method) showed elevated levels of PCDD/F emission factors only. The dominant congeners were OCDD, OCDF, 1,2,3,4,6,7,8-HpCDF and 1,2,3,4,5,7,8-HpCDD. The PCDF ratios in samples from thermal processes and solid phase samples were 69% and 70%, respectively. The ratio of OCDD congener (about 23.5%) was higher than that of other congeners in both solid and liquid phase wastes. These results can be used as a useful reference for the establishment of the PCDD/F inventory and their management plans.

National monitoring of PCDD/DFs in environmental media around incinerators in Korea.

To examine the levels of PCDD/DFs pollution in environmental samples in the vicinity of various incinerators, the levels of PCDD/DFs in air and soil samples collected near 17 incinerators and stack emission gases were investigated between 2003 and 2006. A total of 434 soil, 28 stack emission gas, and 38 air samples were analyzed for their PCDD/DFs concentrations. The PCDD/DFs concentrations in the flue gas samples ranged from 0.02 to 16.41 ng I-TEQ/Sm(3), with an arithmetical mean value of 3.13 ng I-TEQ/Sm(3). The PCDD/DFs concentrations in the air samples ranged from 0.032 to 0.965 pg I-TEQ/Sm(3). The soil samples contained between N.D. and 153.23 pg I-TEQ/g-dry, with an average of 7.36 pg I-TEQ/g-dry. These levels were generally consistent with or lower than many previous studies. The average PCDD/DFs levels in the soil samples decrease with increasing distance from the incinerator. From the PCDD/DFs level gradient from each plant, a distance of 500 m is suggested as being under the influence of an incinerator.

Concentration and congener patterns of polychlorinated biphenyls in industrial and municipal waste incinerator flue gas, Korea.

In the present study, individual PCB congeners were determined in the flue gases of 10 industrial and 5 municipal solid waste incinerators using HRGC/HRMS. The total PCBs concentration of all congeners (168 tetra to deca-chlorinated congeners) ranged from 26 to 343 ng/Nm(3), and from 36 to 1095 ng/Nm(3) in industrial waste incinerators (IWI) and municipal solid waste incinerators (MSWI), respectively. The total TEQ concentrations of PCBs, calculated using WHO-TEF values, varied from 0.001 to 0.55 ng-TEQ/Nm(3) and from 0.001 to 8.29 ng-TEQ/Nm(3) in the industrial waste incinerators and municipal solid waste incinerators, respectively. In all samples, the contribution of PCB 126 to total TEQ of PCBs was higher than 87%. The homologue pattern of PCBs in the incinerator flue gas samples was generally dominated by tetra- and penta-CBs. The distribution of other homologues was less than 15% in most of the incinerators. The fraction of co-PCBs against to total PCBs ranged from 1% to 19% and from 2% to 31% in IWI and MSWI flue gas samples. Results of the present study reveal that the presence of non-ortho PCB congeners in the flue gas originated form the combustion process.