Formation and Inventory of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans and Other Byproducts along Manufacturing Processes of Chlorobenzene and Chloroethylene.

Chlorinated organic chemicals are produced and used extensively worldwide, and their risks to the biology and environment are of increasing concern. However, chlorinated byproducts [e.g., polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs)] formed during the commercial manufacturing processes and present in organochlorine products are rarely reported. The knowledge on the occurrences and fate of unintentional persistent organic chemicals in the manufacturing of organochlorine chemical is necessary for accurate assessment of the risks of commercial chemicals and their production. Here, PCDD/Fs were tracked throughout chlorobenzene and chloroethylene production processes (from raw materials to final products) by target analysis. Other byproducts that can further transform into PCDD/Fs were also identified by performing non-target screening. As a result, the PCDD/F concentrations were mostly the highest in bottom residues, and the octachlorinated congeners were dominant. Alkali/water washing stages may cause the formation of oxygen-containing byproducts including PCDD/Fs and acyl-containing compounds, so more attention should be paid to these stages. PCDD/Fs were of 0.17 and 0.21-1.2 ng/mL in monochlorobenzene and chloroethylene products, respectively. Annual PCDD/F emissions (17 g toxic equivalent in 2018) during chlorobenzene and chloroethylene production were estimated using PCDD/F emission factors. The results can contribute to the improvement of PCDD/F inventories for the analyzed commercial chemicals.

Analysis and risk assessment of vinyl chloride emitted from aerosol products.

The objectives of this study were to develop a novel analytical method for quantifying vinyl chloride (VC) emitted from aerosol products, to provide analytical data on VC in aerosol products, and to evaluate consumer VC exposure by aerosol products. Our quantitative method involves absorbing VC into dimethyl sulfoxide and analyzing it using headspace gas chromatography/mass spectrometry. The correlation coefficients of the VC calibration curves were ≥ 0.9994 in the range of 0.16-80 µg/mL VC standard gases, which were prepared under either nitrogen or emission gases containing dimethyl ether or liquid petroleum gas. VC concentrations in these emission gases were calculated using a VC calibration curve from standard gases prepared under nitrogen; they were within ± 10% of the actual concentrations. We analyzed 39 household aerosol products; VC concentrations of 0.095, 0.098, and 0.28 µg/L were detected in three polyvinyl chloride spray paints. Consumer VC inhalation exposure level was estimated through an exposure scenario, and the hazard quotient was confirmed to be very low when comparing the exposure level with a cancer risk level of 10-5 for inhaled VC. These results suggest that the human health risk from VC in spray paint was low.

[Research on the standard limits for vinyl chloride and trichloroethylene in the "Standards for Drinking Water Quality（GB5749-2022）" in China].

The usage of vinyl chloride and trichloroethylene in China has been increasing year by year, and they have been detected in both drinking water and environmental water, making them important environmental pollutants. Based on the latest research results on the health effects of vinyl chloride and trichloroethylene, the newly issued, "Standards for Drinking Water Quality (GB5749-2022)" in China has adjusted the standard limit of vinyl chloride from 0.005 mg/L to 0.001 mg/L and the standard limit of trichloroethylene from 0.07 mg/L to 0.02 mg/L. This article analyzed and discussed the relevant technical contents for determining the above standard limits, including the levels and exposure conditions of vinyl chloride and trichloroethylene in the water environment, health effects, derivation of safety reference values, and determination of hygiene standard limits. Suggestions were also made for the implementation of this standard.

Detecting vinyl chloride by phytoscreening in the shallow critical zone at sites with potential human exposure.

Chlorinated ethene (CE) contaminants are widespread in groundwater, and the occurrence of vinyl chloride (VC), among others, is a well-known issue due to its mobility, persistence, and carcinogenicity. Human exposure to VC may occur through inhalation after soil vapor intrusion into buildings at sites with shallow underground contamination. Soil vapor intrusion risk is traditionally assessed through indoor air and sub-slab sampling (direct evidence) or soil gas and groundwater surveys (indirect evidence). Phytoscreening (sampling and analysis of tree trunk matrices) was proven as a cost-effective alternative technique to indirectly detect shallow underground contamination by higher chlorinated ethenes and subsequent vapor intrusion risk. However, the technique has appeared barely capable to screen for the lower chlorinated VC, likely due to its fugacity and aerobic bio-degradability, with only one literature record to date showing successful detection in trees. We applied phytoscreening at two sites with severe CE contamination nearby residential buildings caused by illegal dumping of chlorinated pitches from petrochemical productions. The two sites show variable amounts of VC in the shallow groundwater (1e2 to 1e4 µg/L), posing potential sanitary risk issues. Former soil gas surveys did not detect VC in the vadose zone. At both sites, we sampled trunk micro-cores and trunk gas from poplar trees close to contaminated piezometers in different seasons. VC was detected in several instances, disproving the shared literature assumption of the inefficacy of phytoscreening towards this compound. Factors influencing the detectability of VC and other CEs in trees were analyzed through linear regressions. Two different conceptual models were proposed to explain the effective uptake of VC by trees at the two sites, i.e., direct uptake of contaminated groundwater at the first site and uptake of VC from an anoxic vadose zone at the second site. In planta reductive dechlorination of CEs is not expected based on current literature knowledge. Thus, the detection of VC in trunks would indicate its occurrence in the shallow underground, suggesting higher screening effectiveness of phytoscreening compared to soil gas; this has implications for indirect vapor intrusion risk assessment.

Distribution characteristics and health risk assessment of volatile organic compounds in the groundwater of Lanzhou City, China.

Volatile organic compounds (VOCs) typically exist in the aqueous environment due to global anthropogenic activities. The distribution and contaminated profile (or characteristics) of VOCs in the groundwater of Lanzhou, China, were investigated in this study. Groundwater samples were collected from 30 sampling points in December 2015, and a total of 17 VOCs were analyzed by purge and trap gas chromatography-mass spectrometry. Thirteen types of VOCs were detected at 29 sampling points in the study area. Of these, dichloromethane and toluene, which were found at 22 sampling points, had the highest detection frequency (73.3%), followed by benzene (66.7%), 1,2-dichloroethane (50%), and xylenes (50%). The highest average concentration among the detected VOCs was found for chloroform (5151.5 µg/L). The spatial distribution of VOC contamination in four major urban areas of Lanzhou and the variation in VOC concentration caused by land use transitions were also analyzed. The results showed that Xigu district was the most polluted area in Lanzhou, mainly due to land use for industrial proposes. On the contrary, the samples for Anning district showed lower VOC concentrations because of better groundwater quality, which is associated with the absence of manufacturing industries in this region. The health risk assessment model developed by the United States Environmental Protection Agency was employed in this study to evaluate safety for drinking water use. This study found that despite considering the volatilization of VOCs from water due to heating, six sampling points (G05 in Qilihe district; G07 and G09 in Xigu district; G16, G17, and G15 in Chengguan district) showed non-carcinogenic risks, ranging from 1.63 to 14.2, while three points (G16 in Chengguan district, and G10 and G07 in Xigu district) exhibited high carcinogenic risks for human health, ranging from 2.94 × 10-4 to 6.85 × 10-4. Trichloroethylene, tetrachloroethylene, and 1,2-dichloroethylene were identified as the dominant VOCs, presenting high non-carcinogenic risk. 1,2-dichloroethane and vinyl chloride were the primary factors for high carcinogenic risk. The high-risk areas were concentrated in Xigu and Chengguan districts, suggesting the need to alert the relevant local government departments.

A Luminescent 3d-4f-4d MOF Nanoprobe as a Diagnosis Platform for Human Occupational Exposure to Vinyl Chloride Carcinogen.

A luminescent nanoprobe based on a lanthanide-transition heterometallic metal-organic framework (MOF) is first designed for specific detection of urinary thiodiglycolic acid (TDGA) which is the biomarker of carcinogenic vinyl chloride monomer (VCM) and represents the internal dose of human exposure to VCM. The nanoprobe demonstrates high selectivity to TDGA with about 27.5-fold luminescence enhancement. It also displays excellent sensitivity with a detection limit as low as 89 ng·mL-1 and fast response to TDGA within 4 min, while refraining from the interference of other coexisting species in urine. Such good sensing performance enables the nanoprobe to practically monitor TDGA levels in human urine. Moreover, a portable urine dipstick based on the sensor is developed to conveniently evaluate individuals' intoxication degree of VCM. This fast, sensitive, and selective nanoprobe has promising potential to be a useful tool for point-of-care diagnosis of disease associated with VCM exposure.

Exploring a new method for the biological monitoring of plastic workers exposed to the vinyl chloride monomer.

Vinyl chloride monomer (VCM) is widely used in the production of polyvinyl chloride (PVC) plastics. VCM is recognized as a confirmed human and animal carcinogenic compound. Recent studies have reported poor health of plastic workers, even having exposure at concentrations below the permissible limit to VCM. There has not been any study regarding exposed workers to VCM in Iran. Similarly, no information exists as to the biological monitoring of such workers. The main purpose of this study was to conduct a thorough occupational and biological monitoring of Iranian plastic workers exposed to VCM.A total of 100 workers from two plastic manufacturing plants (A and B) in Tehran along with 25 unexposed workers as controls were studied. The personal monitoring of all nonsmoking workers exposed to VCM at two plastic manufacturing plants (A and B) was performed in the morning shift (8 a.m. to 4 p.m.) according to the National Institute For Occupational Safety And Health method no. 1007.Biological monitoring of workers was carried out through collection of exhaled breath of all exposed and control workers in Tedlar bags and with a subsequent analysis using gas chromatography-flame ionization detector.Not only the mean occupational exposure of workers to VCM at plant A was higher than the respective threshold limit value but also the statistical significance was higher than workers at plant B. Similarly, VCM concentration in exhaled breath of workers at plant A was also statistically significantly higher than at plant B. Correlation of occupational exposure of all workers to vinyl chloride with its concentration in exhaled breath was statistically significant.This is the first study on biological monitoring for exposed plastic workers to VCM using exhaled breath. On the basis of the results in this study, a novel method of biological monitoring of plastic workers was proposed.

[Assessment of carcinogenic risks to workers of the main enterprises of the Irkutsk region].

The purpose of research is the assessment of the individual cancer risk (ICR) for workers of the basic occupations in key branches of industry of the Irkutsk region. There was executed the calculation of ICR levels for workers of the basic occupations of the aircraft industry, aluminum smelters and vinyl chloride production plants. The estimation of the exposure for workers was carried out according to long-term time-weighted average concentrations in the air of the working area, for the population - on annual average concentrations in the ambient air. To assess the risk that is not associated with the profession, the dose was calculated for the period of life (70 years). When calculating the toxicant doses in the working area there were used the "standard" indices ofpulmonary ventilation for adults, body weight, the work experience in the contact with carcinogens of 30 years, the number of days in the contact of 240, the duration of the working time 8 or 12 hours (in accordance with the working hours) duration. ICR for the Irkutsk population amounted of 3.08E-04, in Shelekhov - 4.8E-05, Sayansk - 1.1E-05. The amount of risk depends on the content offormaldehyde in all territories and chromium VI in cities of Irkutsk and Shelekhov. ICR for workers of basic occupations of studied plants in dozens of times are higher than for the urban population. Priority carcinogens are: chromium VI, nickel, formaldehyde, silicon dioxide -for the aircraft plant employees; 1,2-dichloretan, vinyl chloride - for the workers of vinyl chloride production plant; benzopyrene - for the aluminum smelter workers.

[Clinical and neurophysiological peculiarities of health disorders in workers in dependence on the vinyl chloride exposure load].

Results of the clinical and neurophysiological examinations of 42 workers with operating history at the chemical plant exposed to vinyl chloride (VC) are presented. The purpose of research was the identification ofpeculiarities of clinical manifestations and disorders of the functional activity of the brain in workers at the vinyl chloride production, with taking into account the exposure toxic load (ETL). There were made clinical and electroencephalographic examinations with the detection of cognitive evoked potentials (CEP) and statistical analysis of results with the use of the Mann-Whitney U-test, Fisher's F-test, calculation of Spearman's correlation coefficient. The features in clinical picture of the pathology of the nervous system were detected in the form of asthenic disorders with cognitive impairment and autonomic dysfunction syndrome. There was established the increase in the cognitive impairment rate (p = 0.03), the decline in a-EEG activity (p = 0.01) and the worsening of indices of the amplitude (p = 0.011) and latency (p = 0,05) of CEP in extremely high level of ETL in comparison with same indices in the group with moderately high ETL. In the first group there was revealed a statistically significant exceedance of the frequency of hypertension - by 1.6 times, skin diseases - by 9 times, chronic subatrophic rhino-pharyngitis by 1.4 times in comparison with cases from the second group. In the group with moderately high level of ETL there was established the statistically significant inverse correlationship between the ETL and the index of P300 amplitude from the left side (r = -0.38, p = 0.019) and in the group with extremely high level ETL - between ETL and index of the ß2 - rhythm (r = - 0.73, p = 0.0008).

[ASSESSMENT OF THE CYTOKINE STATUS IN EMPLOYEES IN CONDITIONS OF CHRONIC EXPOSURE TO VINYL CHLORIDE].

In the article there are presented the results of the evaluation of cytokine profile in males working in the production of vinyl chloride (trained workers without signs of disorders of the neuropsychic status and persons with early signs of neurointoxication with vinyl chloride, characterized by asthenic (emotional lability) disorder with the autonomic dysfunction). There are established differences of pro- and anti-inflammatory responses in workers in dependence on the severity of disorders of the neuropsychic status. The most pronounced imbalance of cytokines was in workers with initial manifestations of neurointoxication with vinyl chloride. The increase in the concentration of pro-inflammatory cytokines (IL-1ß, IL-8, TNF-α) in trained employees without signs of disorders of the neuropsychic status is the one of the early and sensitive indices characterizing the formation ofthe body's resistance to exposure of adverse factors of production.

[To the question of the optimization of methods for detection of vinyl chloride and 1,2-dichloroethane, and their metabolites in biological fluids in workers involved in production of polyvinyl chloride].

There is considered the improvement of methodological approaches to the gas chromatographic methods- of the detection of vinyl chloride and 1,2-dichloroethane and their metabolites--chloroethanol and monochloroacetic acid in biological fluids. There were evaluated such metrological characteristics of methods, as repeatability, interlaboratoty precision, relevance and accuracy. The value of relative expanded uncertainty does not exceed 30%. There are reported optimal regimes of gas chromatographic analysis, conditions for sample preparation. The results of the contents ofthese chemical compounds and their metabolites in biological fluids from persons working in contact with chlorinated hydrocarbons are presented These techniques can be used for the detection ofthe fact of exposure to toxic substances, assessment of the level of exposure and biomonitoring.

[Liver angiosarcoma from past exposure to vinyl chloride: a case report]. / Angiosarcoma epatico da pregressa esposizione a cloruro di vinile monomero: un case report.

BACKGROUND: Experimental data and large occupational cohort studies in polyvinyl chloride (PVC) manufacturing plants have shown that vinyl chloride monomer (VCM) at high environmental concentrations, such as those measured in western chemical companies at least until the mid-1970's can cause liver angiosarcoma. OBJECTIVE: To describe a recent, accurately diagnosed case of fatal liver angiosarcoma, for which it was possible to establish the causal relationship with past VCM exposure. RESULTS: The deceased subject had been working as blue-collar for at least eleven years (1968-1979) in a PVC plant. VCM exposure was high on average and very high during autoclave cleaning, compared with VCM air measurements reported in those years at plants in Europe and the United States. The latency period was about 40 years. The duration of exposure, the cumulative exposure and the latency described were similar to those associated in the scientific literature with an excess risk for liver angiosarcoma. CONCLUSION: The Italian Workers' Compensation Authority (INAIL) has already acknowledged the occupational origin of this neoplastic disease with clear advantages for all parties concerned, not only in economical terms.

The impact of vinyl chloride exposure on the health of Italian workers: an evaluation from SIREP compliance data.

The aim of the study is to investigate exposures to vinyl chloride monomer (VCM) at workplace in Italy and the related burden of diseases. Measurements data was collected from a nation-wide occupational exposure registry (SIREP, 1996-2016). Potentially exposed workers were estimated for some industrial sectors. Concurrent exposures were investigated using cluster analysis. Proportionate mortality ratios were calculated linking data to national mortality statistics (2005-2015). Overall 8,460 measurements were analyzed. Most exposures occurred in the manufacture of chemicals and plastic products. A total of 12,148 workers potentially exposed was estimated (64% male). Concurrent exposures were detected frequently (83%). An elevated proportion of deaths for liver cancer was found in male exposed workers. Although VCM is a known carcinogen for humans, there are still many exposure situations, albeit at low doses, in the chemical and plastic industries.

Phthalate migration and its effects on poly(vinyl chloride)-based footwear: pathways, influence of environmental conditions, and the possibility of human exposure.

The study of phthalate migration in footwear is important from an environmental viewpoint and the consumer health perspective as it remains in direct contact with the user for a long time. In this research article, the migration of phthalate, specifically di-(2-ethylhexyl) phthalate (DEHP), from the poly(vinyl chloride) (PVC) shoe sole to the attached leather insole has been studied for six months under different environmental conditions. After one month, the DEHP concentration in the PVC sole decreased by 45-58%, and that in the leather insole increased from 0.35 mg g-1 to 38-58 mg g-1. After six months, about 90% of the DEHP has been lost from the PVC sole, and that in the leather insole reached close to its initial value (value before the experiment). The migration rate depends on the environmental conditions and the presence of phthalate soluble solvents in the sole-adhesive-insole system of the footwear. The influence of DEHP migration on the physicochemical characteristics of the PVC sole and leather insole has been studied by Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), thermo-gravimetric analysis (TGA), and differential scanning calorimetry (DSC). The migration and emission pathways of DEHP, the influence of environmental conditions, and the possibility of human exposure to phthalate through footwear are discussed.

Enrichment and characterization of a trichloroethene-dechlorinating consortium containing multiple "dehalococcoides" strains.

A microbial consortium that reductively dechlorinates trichloroethene, cis-1,2-dichloroethene (cis-DCE), and vinyl chloride (VC) to ethene with methanogenesis was enriched from chloroethene-contaminated soil from Japan. Dechlorination activity was maintained for over 4 years. Using quantitative polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) analysis targeting the "Dehalococcoides" 16S rRNA gene, four strains were detected. Their growth and dechlorination activities were classified into two types: one that grows by converting cis-DCE to ethene and the other that grows by converting cis-DCE to VC. Then, the vcrA and bvcA genes encoding cis-DCE/VC reductive dehalogenases were detected. Inhibitors of methanogenesis (2-bromoethanesulfonate) and sulfidogenesis (molybdate) led to accumulation of cis-DCE and of VC respectively. These results suggest that methanogens and sulfate-reducing bacteria can play a significant role in dechlorination by "Dehalococcoides."

Anaerobic degradation of vinyl chloride in aquifer microcosms.

The anaerobic degradation potential at a chloroethene-contaminated site was investigated by operating two anoxic column aquifer microcosms enriched in iron(III). One column was fed with vinyl chloride (VC) only (column A) and one with VC and acetate (column B). In column A, after about 600 pore volume exchanges (PVEs), VC started to disappear and reached almost zero VC recovery in the effluent after 1000 PVEs. No formation of ethene was observed. In column B, effluent VC was almost always only a fraction of influent VC. Formation of ethene was observed after 800 PVEs and started to become an important degradation product after 1550 PVEs. However, ethene was never observed in stoichiometric amounts compared with disappeared VC. The average stable isotope enrichment factor for VC disappearance in column A was determined to be -4.3‰. In column B, the isotope enrichment factor shifted from -10.7 to -18.5‰ concurrent with an increase in ethene production. Batch microcosms inoculated with column material showed similar isotope enrichment factors as the column microcosms. These results indicated that two degradation processes occurred, one in column A and two in parallel in column B with increasing importance of reductive dechlorination with time. This study suggests that in addition to reductive dechlorination, other degradation processes such as anaerobic oxidation should be taken into account when evaluating natural attenuation of VC and that isotope analysis can help to differentiate between different pathways of VC removal.

Effect of pore velocity on biodegradation of cis-dichloroethene (DCE) in column experiments.

Column experiments were conducted to evaluate the effect of pore velocity on the extent of biodegradation of cis-dichloroethene (cis-DCE) during transport in porous media. Columns were filled with homogeneous glass beads and inoculated with a culture capable of complete dechlorination of tetrachloroethene to ethene. A constant concentration of cis-DCE was maintained in the columns' influent. Three different pore velocities were tested in duplicate, subjecting each column to a constant velocity. At high flow velocity, degradation of cis-DCE to ethene was nearly complete within the residence time of the columns. However, at medium and low flow velocities, incomplete dechlorination was observed. After 7 weeks, DNA was harvested from the columns to determine differences in the microbial populations. Results suggest that Dehalococcoides sp. were present in higher quantities in the high-velocity columns, consistent with the observed dechlorination. These results suggest that, at contaminated groundwater sites, heterogeneity of groundwater velocity may be one factor that contributes to heterogeneous distribution of biological activity.

The use of multizone models to estimate an airborne chemical contaminant generation and decay profile: occupational exposures of hairdressers to vinyl chloride in hairspray during the 1960s and 1970s.

Vinyl chloride (VC) was used as a propellant in a limited percentage of aerosol hairspray products in the United States from approximately 1967 to 1973. The question has arisen whether occupational exposures of hairdressers to VC-containing hairsprays in hair salons were sufficient to increase the risk for developing hepatic angiosarcoma (HAS). Transient two-zone and steady-state three-zone models were used to estimate the historical airborne concentration of VC for individual hairdressers using hairspray as well as estimated contributions from other hairdressers in the same salon. Concentrations of VC were modeled for small, medium, and large salons, as well as a representative home salon. Model inputs were determined using published literature, and variability in these inputs was also considered using Monte Carlo techniques. The 95th percentile for the daily time-weighted average exposure for small, medium, and large salons, assuming a market-share fraction of VC-containing hairspray use from the Monte Carlo analysis, was about 0.3 ppm, and for the home salon scenario was 0.1 ppm. The 95th percentile value for the cumulative lifetime exposure of the hairdressers was 2.8 ppm-years for the home salon scenario and 2.0 ppm-years for the small, medium, and large salon scenarios. If using the assumption that all hairsprays used in a salon contained VC, the 95th percentile of the theoretical lifetime cumulative dose was estimated to be 52-79 ppm-years. Estimated lifetime doses were all below the threshold dose for HAS of about 300 to 500 ppm-years reported in the published epidemiology literature.

Inhalation exposure to volatile organic compounds in the printing industry.

This study reports on the occupational inhalation exposure to VOCs of workers in the Kuwaiti printing industry. Using the evacuated canister methodology, we targeted 72 VOCs in three printeries and compared the concentrations to previous reports and relevant occupational exposure levels (OELs). We found that recent efforts in the printing industry to reduce VOC usage had been successful, as concentrations of key hazardous VOCs were substantially lower than anticipated. On the other hand, nearly all target VOCs were found. Non-production areas were sampled along with the offset printing areas, another strength of this study, and revealed exposures to hazardous VOCs among administers and digital printer and CTP operators. Exposure to ototoxic VOCs amounted to 1-3% of the OEL, consisting mostly of ethylbenzene, which was likely in use in two of the study printeries. Exposure to carcinogenic or probably carcinogenic VOCs was 15-20% of the OEL at four locations across the three printeries, consisting mostly of vinyl chloride and benzyl chloride. Vinyl chloride VOC was partially sourced from outdoors, but was also likely used inside the study printeries. Interestingly, concentrations of vinyl chloride were similar in most sampling locations to that of CFC-114, a CFC banned by the Montreal Protocol and not commonly used as a refrigerant. This unexpected finding suggests further study is warranted to identify the use of these VOCs in printeries. Exposure to hazardous VOCs up to nearly 50% of the OEL, consisting largely of bromoform and vinyl chloride. Bromoform was found in all the study printeries, sourced partially from outdoor air. The higher concentrations found inside the study printeries likely resulted from the use of the desalinated water for washing. This finding raises of emissions from sources other than blanket washes, and inks, etc. adding to the total VOC load in printery indoor air. Implications: Results from this study indicate that efforts to reduce worker exposure to VOCs particularly dangerous to human health in recent years have been successful, but there is still much to be done to protect workers. Exposures to ototoxic and carcinogenic VOCs were identified, among both production and non-production workers. Unexpected findings included the apparent use in printing activities of the carcinogen vinyl chloride and CFC-114, banned under the Montreal Protocol. Observed lapses in safety procedures included failure to utilize ventilation systems and closing doors between work areas, indicating management and worker education should remain a priority.

Assessment of a groundwater contamination with vinyl chloride (VC) and precursor volatile organic compounds (VOC) by use of a geographical information system (GIS).

Regarding the health effects of volatile organic compounds (VOC) and their decomposition products (particularly vinyl chloride (VC)) under chronic low-dose exposure, VOC groundwater contaminations are seen to be an ongoing public health issue. This article presents results of a long-term investigation surveying VOC and VC groundwater contamination upstream of a large groundwater works in Cologne, Germany. For 10 years a contaminated aquifer has been monitored for different VOC and for VC. In total, 255 samples have been taken to assess both the 3-dimensional distribution and the temporal dynamics of the contaminants. VOC and VC precursor substances have been measured by means of pentane-liquid-liquid-extraction, GC and ECD, VC by means of derivatisation to 1,2 dibromochloroethane, GC, ECD, and by purge and trap technique and GC-MS-coupling. For spatial analysis all test results and additional hydrogeological attribute data have been transferred to a GIS. The spatial VOC distribution has been assessed by use of kriging interpolation indicating a decrease of the initial contaminants in time. A cluster analysis allowed to distinguish several independent contaminations within the large contamination area. The VC contamination was increasing. Anaerobic microbial dechlorination of VOC and subsequent VC accumulation were seen to be as credible from several indications (VC presence, downstream change of tetra/trichloroethylene-ratio and anaerobic conditions in the aquifer, high Fe(2+)- and Mn(2+)-concentrations). There was no statistically significant vertical differentiation of VOC and VC concentrations. The VOC load within the different water protection zones of the waterworks could be assessed.