Occurrence of N-nitrosamines in the atmosphere and human health risk: A case study in an urban area of Chuncheon, Gangwon State, South Korea.

This study aimed to investigate the occurrence of eight nitrosamines (NAs) in particulate (PM2.5) and gaseous phases and assess the human health risk associated with these compounds in an urban area of Chuncheon, Gangwon State, South Korea, across four sampling seasons. The findings revealed that the total concentrations of eight NAs measured during the sampling period exceeded the public health recommendation of 0.3 ng/m3 provided by the Norwegian Institute of Public Health, indicating a potential human health risk from NA exposures. In particular, the average total NA concentration observed in the gaseous samples during the winter of 2021 was 18.1 ± 6.46 ng/m3. The primary emission sources could potentially impact the concentrations of NAs in the atmosphere due to their significant positive correlation with primary emission species such as NO2, CO, and SO2. Moreover, the levels of particulate NAs during the summer were negatively correlated with O3, suggesting that their formation might be influenced by ozonation in the aqueous aerosol phase. In addition, the total NA concentrations measured in the gaseous phase were four to six times higher than those measured in the PM2.5 phase throughout the sampling period. Thus, domestic sources have the potential to impact the pollution levels of the research area more significantly than long-range atmospheric transport. In particular, the highest concentrations of NAs in the gas phase were observed during the winter, while the lowest concentrations were recorded in the summer, possibly influenced by photolysis. Nevertheless, the study suggested that tertiary amines might contribute to the presence of gaseous NAs in sunlight. Consequently, further studies focusing on the occurrence of tertiary amines in the gas phase should be considered. The cumulative lifetime cancer risks estimated from inhalation exposure exceeded the acceptable risk level of 10⁻6 for all age groups across all four seasons. Therefore, it is crucial to implement effective control measures to mitigate potential health risks associated with exposure to NAs.

Use of flat-sheet membrane extraction with a sorbent interface for solvent-free determination of BTEX in water.

An analytical method for solvent-free determination of benzene, toluene, ethylbenzene, and xylenes (BTEX) in water using flat-sheet membrane extraction with a sorbent interface (MESI) coupled to GC-MS was established by optimizing the flow rates of the donor (20 ml water) and acceptor (helium) phases and extraction temperature. BTEX compounds permeated through a nonporous silicone membrane and evaporated into the acceptor phase were purged into a cryofocusing trap (-30 °C) with helium gas. Enriched compounds were thermally desorbed into a capillary gas chromatograph and detected with a mass spectrometer. The optimum flow rates of the donor and acceptor phases were set at 1.5 and 55 ml min(-1), respectively, and the temperature of the membrane extraction module was maintained within the 28-30 °C range. The method as established showed low method detection limits (MDLs:∼0.1 µg l(-1)) and highly linear calibration curves (r(2)>0.998) for all of the four compounds. High repeatability (relative standard deviation <∼5%) and a reasonably high extraction recovery (62-78%), after a single pass of the sample through the extraction module, also were established. Further, the method's high compatibility with the purge and trap (P&T) method indicates its applicability to field measurement. Other advantages include rapidity, simplicity, and a ready extendibility to automated on-line monitoring.

Ingestion exposure to nitrosamines in chlorinated drinking water.

OBJECTIVES: N-Nitrosodimethylamine (NDMA) is classified as a probable human carcinogen by the United States Environmental Protection Agency (US EPA) and is formed during the chlorination of municipal drinking water. In this study, selected nitrosamines were measured in chlorinated drinking water collected from Chuncheon, Kangwon-do, Republic of Korea, and a risk assessment for NDMA was conducted. METHODS: Twelve water samples were collected from 2 treatment plants and 10 household taps. Samples were analyzed for 6 nitrosamines via solid-phase extraction cleanup followed by conversion to dansyl derivatives and high-performance liquid chromatography-fluorescence detection (HPLC-FLD). Considering the dietary patterns of Korean people and the concentration change of NDMA by boiling, a carcinogenic risk assessment from ingestion exposure was conducted following the US EPA guidelines. RESULTS: NDMA concentrations ranged between 26.1 and 112.0 ng/L. NDMA in water was found to be thermally stable, and thus its concentration at the end of boiling was greater than before thermal treatment owing to the decrease in water volume. The estimated excess lifetime carcinogenic risk exceeded the regulatory baseline risk of 10(-5). CONCLUSIONS: This result suggests that more extensive studies need to be conducted on nitrosamine concentration distributions over the country and the source of relatively high nitrosamine concentrations.

Seasonal variations in the household exposures of Korean housewives to volatile tap water disinfection by-products.

This study was conducted to compare housewives' winter and summer exposures to volatile disinfection by-products (DBPs) in chlorinated tap water. A total of 60 households were visited for this purpose: 27 in winter and 33 in summer. Each subject was given a questionnaire regarding general tap water use, household ventilation time, and activities related to water use. Tap water, household air, and exhaled breath samples were also collected during the visits. All of the subjects answered that they consumed tap water after either thermal treatment or purification through filtration systems. A longer ventilation time in winter than in summer resulted in a higher inhalation exposure for housewives during that season. Estimated chronic daily intakes calculated for winter and summer showed that in winter, the greatest risk at home is inhalation exposure while resting at home, whereas in summer, it is showering. In both seasons, the ingestion route can be discounted, because tap water is processed before consumption, eliminating the volatile DBPs. From this study, it is evident that the inhalation of household air while resting at home cannot be ignored in risk assessment. Moreover, the fact that water is normally boiled or filtered before use should also be considered.

Distribution and mobility of chromium, copper, and arsenic in soils collected near CCA-treated wood structures in Korea.

Chromated copper arsenate (CCA) is currently the most commonly used wood preservative in Korea. Questions, however, have been raised regarding the potential environmental impacts of metal leaching from CCA-treated wood to soil. Although a number of researchers from other countries have reported that chromium, copper, and arsenic do leach from CCA-treated wood over time, to date few field studies have been performed on those metals in soils adjacent to CCA-treated wood structures in Korea. The present study was conducted to determine the lateral and vertical distributions and accumulation of chromium, copper, and arsenic in soils collected from CCA-treated wood structures. A total of fifty-five composite soil samples were collected from four CCA-treated wood structures of approximately one year in age. The samples were analyzed for physicochemical properties as well as for the total chromium, copper, and arsenic concentrations. The chromium, copper, and arsenic concentrations in soil samples adjacent to the structures were as high as 79.0, 98.9, and 128 mg/kg, respectively, compared to background soil samples (48.2, 26.9, and 6.27 mg/kg, respectively). Arsenic was more mobile in soil than chromium and copper. The concentration gradient of arsenic in soil was observed only to the depth of approximately 5 cm in one year of outdoor exposure, whereas chromium and copper apparently remained near the surface (approximately less than 1 cm) after their release. Future efforts should be made to observe seasonal impacts on the release of metals and incorporate metal speciation into determining more detailed mobility and distribution.

Effect of PCB 126 on hepatic metabolism of thyroxine and perturbations in the hypothalamic-pituitary-thyroid axis in the rat.

The objective of this research was to examine the time- and dose- dependent disturbances in the hypothalamic-pituitary-thyroid (HPT) axis of adult male rats administered a potent coplanar (non-ortho) PCB, 3,3',4,4',5-pentachlorobiphenyl (PCB 126). Adult male Sprague-Dawley rats were administered a single oral bolus dose of 0, 7.5, 75, or 275 microg PCB 126/kg bw dissolved in corn oil. The rats were sacrificed periodically over 22 days. The 7.5-microg/kg dose induced hepatic ethoxyresorufin-O-deethylation EROD activity, but no changes were observed in hepatic uridine diphosphate glucuronyl transferases (UDPGTs) activity or serum TSH, T4, or fT4 concentrations. The two highest doses caused a modest decline in weight gain, induced hepatic EROD and UDPGT activities, increased serum TSH concentrations, and decreased serum T4 and fT4 concentrations. The amount of thyroxine glucuronide formed daily (pM/mg protein) increased linearly with the area-under-the-concentration-curve (AUCC) for PCB 126 in liver (microg/kg/day) and then slowed at the 275-microg/kg PCB 126 dose. Perturbations in the HPT axis were nonlinear with respect to PCB 126 dosing. As expected, an inverse relationship between the AUCC for serum T4 (microg/dl/day) and the AUCC for serum TSH (ng/dl/day) was observed; however, the relationship was highly nonlinear. These data support a mode of action for PCB 126 involving induction of hepatic UDPGTs by the aryl hydrocarbon receptor AhR. However, the dose-response characteristics of the HPT axis are nonlinear and complex, requiring sophisticated tools, such as PBPK models, to characterize dose response.

Formation of disinfection by-products in chlorinated swimming pool water.

The formation of five volatile disinfection by-products (DBPs: chloroform, bromodichloromethane, chloral hydrate, dichloroacetonitrile, and 1,1,1-trichloropropanone) by the chlorination of the materials of human origin (MHOs: hair, lotion, saliva, skin, and urine) in a swimming pool model system was examined. Chlorination reactions took place with a sufficient supply of chlorine residuals (0.84 mg Cl2/l < total chlorine < 6.0 mg Cl2/l) in 300 ml glass bottles containing either ground water or surface water as a reaction medium at 30 degrees C and pH 7.0, for either 24 or 72 h. A longer reaction period of 72 h or a higher content of organic materials led to the increased formation of DBPs. Of the DBPs formed by the reaction, chloroform was a major compound found in both ground and surface waters. The formation of chloroform and bromodichloromethane per unit total organic carbon (TOC) concentration was suppressed when all types of MHOs were added to the surface water that already contained DBP precursors such as humic substances. However, the formation of dichloroacetonitrile was promoted, probably due to the increased degradation reactions of nitrogen-containing compounds such as urea and proteins of human origin. In conclusion, the materials of swimmers' origin including hair, lotion, saliva, skin, and urine add to the levels of DBPs in swimming pool water, and any mitigation measures such as periodic change of water are needed to protect swimmers from elevated exposures to these compounds.