Further studies on impurities in chlorophenols

Polychlorinated Diphenyl Ethers in the Environment: A Review and Future Perspectives

Polychlorinated diphenyl ethers (PCDEs) are a class of synthetic halogenated aromatic compounds, which have gradually attracted widespread attention due to potential environmental risks to humans and ecosystems. This paper presents a literature review of research on PCDEs using PubMed, Web of Science and Google Scholar as search engines/databases with no constraints on publishing year or number. A total of 98 publications on the sources, environmental levels, environmental behavior and fate, synthesis and analysis and toxicology of PCDEs were retrieved. Existing studies have shown that PCDEs widely exist in the environment with the ability of long-range transport, bioaccumulation and biomagnification, which are almost comparable to polychlorinated biphenyls. They can elicit adverse effects including hepatic oxidative stress, immunosuppression, endocrine disorders, growth retardation, malformations, reduced fertility and increased mortality in organisms, among which some seem to be related to the activation of the aryl hydrocarbon receptor. PCDEs can be metabolized into other organic pollutants, such as hydroxylated and methoxylated PCDEs and even polychlorinated dibenzo-p-dioxins and furans through biotransformation, photolysis and pyrolysis reactions in the environment. Compared with reviews on PCDEs published previously, some new information and findings are summarized in this review, such as new sources, current environmental exposure levels, main metabolism pathways in aquatic organisms, acute toxicity data for more species and relationships between structural parameters and toxicity and bioaccumulation potentials of PCDE congeners. Finally, current research deficiencies and future research perspectives are proposed to facilitate the assessment of health and ecological risks of PCDEs.

Biomarker Responses, Gene Expression Alterations, and Histological Changes in Zebrafish (Danio rerio) After In Vivo Exposure to Polychlorinated Diphenyl Ethers

Polychlorinated diphenyl ethers (PCDEs) have been detected in various aquatic matrices, which pose potential threats to aquatic ecosystem security. In this work, both micro and macro analysis methods were used to assess the toxicity of PCDEs to zebrafish. Results indicated that after in vivo PCDE exposure, the oxidative stress and related gene of Danio rerio were significantly changed. The higher concentration or longer exposure time could cause more severe oxidative stress in zebrafish tissues. Compared with among the five tested compounds, more obvious changes in the level of oxidative biomarkers of lower chlorinated PCDEs’ (4-mono-CDE and 4,4′-di-CDE) exposure groups were observed. The integrated biomarker response analysis and gene expression results also indicate a similar trend. Histopathological observation suggested that 4,4′-di-CDE could render liver nuclei enlargement and necrosis, hepatocyte vacuolation, and the development inhibition of ovarian cells. Transmission electron microscope photos showed that 4,4′-di-CDE caused organelle damage in the liver and ovary, including the rupture of the endoplasmic reticulum, swelling of mitochondria, and condensation of chromatin in the liver and mitochondria disappeared significantly in the ovary. The degree of damage is enhanced with the increasing exposure doses. In addition, PCDEs also significantly altered vitellogenin content and related gene (vtg1) expression, suggesting that PCDEs may be estrogen endocrine disruptors. Overall, these results provided some valuable toxicological data of PCDEs on aquatic species.

Polychlorinated diphenyl ethers (PCDEs) in surface sediments, suspended particulate matter (SPM) and surface water of Chaohu Lake, China

Polychlorinated diphenyl ethers (PCDEs) are typical halogenated aromatic pollutants that have shown various toxicological effects on organisms. However, the contamination status of PCDEs in the fresh water lakes of China remains poorly researched. In this study, the levels of 15 congeners of PCDEs in the sediments, suspended particulate matter (SPM) and water of Chaohu Lake were determined. The results showed that the ranges of concentrations of total PCDEs (ΣPCDEs) in the sediment, SPM and water were 0.279 ng g^-1 dry weight (d.w.)-2.474 ng g^-1 d.w., 0.331 ng g^-1 d.w.-2.013 ng g^-1 d.w. and 0.351 ng L^-1-2.021 ng L^-1, respectively. The most abundant congeners found in sediments, SPM and water were 3,3',4,4'-tetra-CDE, deca-CDE and 2,4,6-tri-CDE, with average contributive ratios of 17.36%, 15.48% and 20.63%, respectively. The medium and higher chlorinated PCDEs (e.g., penta- and deca-CDEs) were the dominant congeners in sediments and SPM. The percentages of lower chlorinated PCDEs (e.g., tri-CDEs) in the water were higher than those in the sediments. The combined input of ΣPCDEs from the eight main tributaries to Chaohu Lake was estimated at 6.94 kg y^-1. Strong linear correlations between the concentrations of ΣPCDEs and organic carbon (OC) contents in three type samples from Chaohu Lake suggested OC could influence the distribution of PCDEs in Chaohu Lake substantially. In addition, the calculated average organic carbon normalized partition coefficients (logK_oc) of 15 PCDEs between water and SPM were in the range of 4.55-5.45 mL g^-1. This study confirmed that Chaohu Lake is contaminated by PCDEs.

Toxicity evaluation of 4,4'-di-CDPS and 4,4'-di-CDE on green algae Scenedesmus obliquus: growth inhibition, change in pigment content, and oxidative stress

Polychlorinated diphenyl sulfides and polychlorinated diphenyl ethers are two types of dioxin-like pollutants, which are prevalent in aquatic environments. However, to date, limited information is available regarding their toxicity to green algae. In this study, growth inhibition, effect on pigment content, and oxidative stress potentials of 4,4'-di-CDPS and 4,4'-di-CDE on green algae Scenedesmus obliquus were investigated. The results indicate that the EC₅₀ values of 4,4'-di-CDPS after 24, 48, 72, and 96 h of exposure were 1.736, 1.172, 0.994, and 0.820 mg/L, while the corresponding values for 4,4'-di-CDE were 0.697, 1.087, 0.833, and 0.327 mg/L. As compared to the control group, most of the measured pigment content in algal cells significantly decreased after 96-h exposure to these two chemicals, suggesting their suppressive capability on the photosynthesis process in algal cells. Additionally, oxidative stress occurred as demonstrated by the significantly inhibited activities of the antioxidant enzymes (total superoxide dismutase (T-SOD), catalase (CAT), and glutathione peroxidase (GPx)), and high increases in malondialdehyde (MDA) content in all 4,4'-di-CDE-treated groups and some moderate-dose and high-dose treatments with 4,4'-di-CDPS. Acute toxicity tests and biochemical analysis showed that 4,4'-di-CDE was more toxic than 4,4'-di-CDPS on S. obliquus.

Human exposure to PCDDs and their precursors from heron and tern eggs in the Yangtze River Delta indicate PCP origin

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are highly toxic to humans and wildlife. In the present study, PCDD/Fs were analyzed in the eggs of whiskered terns (Chlidonias hybrida), and genetically identified eggs from black-crowned night herons (Nycticorax nycticorax) sampled from two lakes in the Yangtze River Delta area, China. The median toxic equivalent (TEQ) of PCDD/Fs were 280 (range: 95-1500) and 400 (range: 220-1100) pg TEQ g^-1 lw (WHO, 1998 for birds) in the eggs of black-crowned night heron and whiskered tern, respectively. Compared to known sources, concentrations of PCDDs relative to the sum of PCDD/Fs in bird eggs, demonstrated high abundance of octachlorodibenzo-p-dioxin (OCDD), 1,2,3,4,6,7,8-heptaCDD and 1,2,3,6,7,8-hexaCDD indicating pentachlorophenol (PCP), and/or sodium pentachlorophenolate (Na-PCP) as significant sources of the PCDD/Fs. The presence of polychlorinated diphenyl ethers (PCDEs), hydroxylated and methoxylated polychlorinated diphenyl ethers (OH- and MeO-PCDEs, known impurities in PCP products), corroborates this hypothesis. Further, significant correlations were found between the predominant congener CDE-206, 3'-OH-CDE-207, 2'-MeO-CDE-206 and OCDD, indicating a common origin. Eggs from the two lakes are sometimes used for human consumption. The WHO health-based tolerable intake of PCDD/Fs is exceeded if eggs from the two lakes are consumed regularly on a weekly basis, particularly for children. The TEQs extensively exceed maximum levels for PCDD/Fs in hen eggs and egg products according to EU legislation (2.5 pg TEQ g^-1lw). The results suggest immediate action should be taken to manage the contamination, and further studies evaluating the impacts of egg consumption from wild birds in China. Likewise, studies on dioxins and other POPs in common eggs need to be initiated around China.

Occurrence of polychlorinated diphenyl ethers in Nanjing section of the Yangtze River: level and distribution pattern

Polychlorinated diphenyl ethers (PCDEs) are a group of halogenated aromatic compounds and serious environmental pollutants. In the present study, sediment and water samples from eight sites in Nanjing section of the Yangtze River were characterized with 15 congeners of PCDEs. Concentrations and distributions of these PCDEs in water phase and sediments were analyzed by GC/MS. Results demonstrated that ∑PCDE concentrations were higher in the low water period (1.15-1.80 μg/L) than those in the high water period (0.73-1.30 μg/L) in water phase. Moreover, ∑PCDE concentrations were higher in the low water period (1.58-3.98 μg/kg) than those in the high water period (1.24-3.48 μg/kg) in sediments. A significant linear relationship existed between the ∑PCDE concentrations and TOC contents in sediments, but a poor linearity was found between ∑PCDE concentrations and DOC contents in water phase. Furthermore, the comparison of the percentage compositions in sediments and in water phase showed that CDE-30 (2,4,6-tri-CDE) was the predominant congener in the studied sites, and higher chlorinated congeners accounted for a larger proportion in sediments than those in water phase. In conclusion, the present study demonstrated the prevalent contamination by PCDEs in sediments and water from the Nanjing section of the Yangtze River.

Desorption of sediment-associated polychlorinated dibenzo-p-dioxins, dibenzofurans, diphenyl ethers and hydroxydiphenyl ethers from contaminated sediment

The transport and bioavailability of sediment-associated contaminants are often controlled by the contaminants' desorbing behaviour. This study examines the desorption kinetics of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), diphenyl ethers (PCDEs) and hydroxydiphenyl ethers (HO-PCDEs) from the highly contaminated River Kymijoki sediment in Finland. The desorption kinetics data were generated using Tenax((R)) extraction, and a first-order three-compartment kinetic model was fitted to the data. The desorption data was compared to the previously published accumulation data from this same location to investigate the relationship between the rapidly desorbing fraction (F(r)) and biota-sediment accumulation factors (BSAFs) as well as semipermeable membrane device sediment accumulation factors (SSAFs). The PCDDs, PCDFs, PCDEs and HO-PCDEs were tightly attached to sediment particles and formed a large very slowly desorbing fraction (F(vs)). Rapidly desorbing fractions (F(r)) varied between 0.8% and 8% of total amount in sediment. The size of the desorbing fraction was congener-specific and F(r) decreased with the increasing lipophilicity of congeners. The size of the F(r) was unable to explain the small variation in the BSAFs of Lumbriculus variegatus but may help to explain the observed variation in the SSAFs. To our best knowledge, this study is the first effort to investigate the desorption of PCDDs, PCDFs, PCDEs and HO-PCDEs in field-contaminated sediments. The major finding that the very slow desorption of these chemicals will continue years, provides essential information for the modern risk assessment process.

Bioaccumulation, bioavailability and environmental fate of chlorophenol impurities, polychlorinated hydroxydiphenylethers and their methoxy analogues

The bioaccumulation potential and environmental fate of polychlorinated hydroxydiphenyl ethers (HO-PCDEs; polychlorinated phenoxyphenols, PCPP), the major impurities of chlorophenol formulations and their methoxy analogues (MeO-PCDEs; polychlorinated methoxyanisoles, PCPAs) were investigated. Oligochaete worms (Lumbriculus variegatus) exposed to sediment spiked with a model substance of one HO-hexaCDE (4'-HO-PCDE 161) or its methoxy analogue (4'-MeO-PCDE 161) clearly accumulated the test compounds revealing the potential for environmental risk of HO-PCDEs and MeO-PCDEs. The HO-PCDE tested has earlier been reported as an abundant component in a Finnish chlorophenol formulation (Ky-5) and its methoxy analogue is recognized as an abundant MeO-PCDE in sawmill soil contaminated by the formulation. The occurrence of 4'-HO-PCDE 161 and its methoxy analogue among other HO-PCDEs and MeO-PCDEs in lake mussels (Anodonta piscinalis) incubated in a river contaminated via the manufacture of Ky-5 showed that these compounds are bioavailable and transported in the aquatic environment. Mussel comparison with sediment data pointed to a higher accumulation potential for MeO-PCDEs than for HO-PCDEs. The finding of HO-PCDEs in groundwater samples collected from a groundwater reservoir, which had been contaminated by chlorophenols, points to potential of HO-PCDEs for transport with water in soil.

Levels of chlorinated compounds (CPs, PCPPs, PCDEs, PCDFs and PCDDs) in soils at contaminated sawmill sites in Sweden

Soil samples from five contaminated sawmill sites in Sweden were characterized with respect to chlorophenols (CP), chlorinated phenoxy phenols (PCPP, hydroxylated chlorinated diphenyl ethers), chlorinated diphenyl ethers (PCDE), chlorinated dibenzofurans (PCDF) and chlorinated dibenzo-p-dioxins (PCDD). The composition of chlorinated compounds in the soil samples was compared to the composition of two preservatives commonly used in the Scandinavian wood impregnation industry: the 2,3,4,6-tetrachlorophenol preservative called Ky-5 and the pentachlorophenol preservative Dowicide G. The levels of CPs in the soil samples ranged from 0.1 to 4500 mgkg-1 d.w., PCPPs from <0.15 to 940 mgkg-1 d.w., PCDEs from <38 to 6800 microgkg-1 d.w., PCDFs from 7.4 to 18000 microgkg-1 d.w. and PCDDs from 9.9 to 35000 microgkg-1 d.w. The resulting WHO-TEQ of PCDD/Fs in the soil samples ranged from 0.14 to 3000 microgkg-1 d.w. Despite a wide range of concentrations the congener compositions were similar within tetrachlorophenate and pentachlorophenate contaminated soils respectively. The contamination at each sawmill site may be linked to the use of either a tetrachlorphenol preservative, e.g. Ky-5, or a pentachlorophenol preservative, e.g. Dowicide G. Best-fit calculations were used to compare the chlorinated phenol contents of the preservatives to those of the soil samples. This revealed a positive correlation between the hydrophobicity (logKow) of contaminants and the ratio of their levels in soil to preservatives. The relative abundance of the chlorinated compounds varied greatly between the five sites studied, suggesting that their transport parameters differ substantially.

Prediction of vapour pressures for halogenated diphenyl ether congeners from molecular descriptors

BACKGROUND, AIM AND SCOPE

Polychlorinated diphenyl ethers (PCDE) and polybrominated diphenyl ethers (PBDE) have both been identified as environmental contaminants. The physical properties are important in determining the distribution and fate of organic contaminants in the environment. The purpose of the present investigation was to characterise halogenated diphenyl ethers using computationally derived descriptors, and to develop calibration models for the vapour pressure from published experimental data.

METHODS

Experimental data for vapour pressures were obtained from the literature. The chemical structure of each PCDE and PBDE congener was optimised prior to descriptor generation. The data analysis was performed using principal component analysis (PCA) and partial least squares regression (PLSR). The calibration models were validated with external test sets.

RESULTS AND DISCUSSION

All congeners of PCDEs and PBDEs were characterised by 795 molecular descriptors and two principal components could account for about two thirds of the variance within each group. Bilinear calibration models were developed that could explain 99.4% of the variance in the external validation test sets. Vapour pressures were subsequently predicted for all congeners that were adequately described by these calibration models. The type and number of halogen atoms in the molecule were the main factors influencing the vapour pressures of halogen substituted diphenyl ethers, but the variations in substitution pattern was also shown to be a significant factor.

CONCLUSIONS

The molecular descriptor patterns of halogenated aromatic compounds such as diphenyl ethers can be described and interpreted using principal component analysis (PCA). The major sources of variation in the descriptor spaces for PCDEs and PBDEs are the same as those contributing to the differences in vapour pressure, similar to what has previously been reported for the PCBs. The bilinear calibration models for vapour pressure presented here, has a standard error of prediction that is lower than what is reported as the experimental uncertainty or observed as deviations between experimental investigations. The estimated prediction errors are expected to be within the reported boundaries when the models are applied to new objects within the same molecular descriptor space, and model predictions can hence extend the current database of experimental values.

RECOMMENDATIONS AND OUTLOOK

The results from this investigation and others show that the establishment of quantitative structure-property relationships (QSPR) is a viable approach to estimate physical properties for halogenated diphenyl ethers. It is easy to foresee an increased need for using QSPR estimation methods in the future, for evaluation of the environmental fate for organic pollutants. Despite method developments and automation, it is unlikely that laboratory determinations can cope with the pace that new pollutants are identified.

An investigation of the in vivo formation of octachlorodibenzo-p-dioxin

The in vivo formation of dioxins from chemical precursors was investigated in rats. Sprague-Dawley rats were fed pentachlorophenol or a predioxin in peanut oil for 14 days. Mass balance calculations indicated that pentachlorophenol was not converted to dioxins; however, the predioxin, nonachloro-2-phenoxyphenol, was converted to OCDD. Conversion of the predioxin ranged from 0.5% to 153% and depended on the amount of predioxin and OCDD present in the diet. The analytical procedures used for sample preparation did not appear to cause conversion of the predioxin to OCDD. The mechanism for biological conversion may be enzymatic or spontaneous.

Vapour pressures, aqueous solubilities, Henry's law constants, partition coefficients between gas/water (Kgw), n-octanol/water (Kow) and gas/n-octanol (Kgo) of 106 polychlorinated diphenyl ethers (PCDE)

Modelling the environmental fate of persistent organic pollutants like polychlorinated diphenyl ethers (PCDE) requires the knowledge of a number of fundamental physico-chemical properties of these compounds. We report here the physico-chemical properties of 106 PCDEs, which are over 50% of all possible congeners. Vapour pressures P(OL), water solubilities S(H2O), and n-octanol/water partition coefficients K(OW) were determined with chromatographic methods. With these experimental data the Henry's law constants H, gas/water K(GW) and gas/n-octanol K(GO) partition coefficients were calculated. Vapour pressures and water solubilities and n-octanol/water partition coefficients of the PCDEs are close to those of similar groups of organochlorine compounds like polychlorinated biphenyls (PCBs) and dibenzofurans (PCDFs). A similar environmental fate can be predicted and was partially already been observed.

Polychlorinated diphenylethers: origin, analysis, distribution, and toxicity in the marine environment

PCDEs are present as impurities in chlorophenol preparations, which are often used as wood preservatives. Other sources of PCDEs such as municipal waste incinerators seem to be of minor importance. It is estimated that, worldwide 250-2500 metric tons of PCDEs have been produced, which is a lesser amount compared to the production figures of polychlorinated biphenyls (PCBs), polybrominated diphenylethers (PBDEs), or polychlorinated naphthalenes (PCNs). The required analytical methods are rather complex and are comparable to methods used for polychlorinated dibenzo-p-dioxins (PCDDs) and furans (PCDFs). Gas chromatography with low resolution or high resolution mass spectrometry or with electron-capture detection is recommended for the final determination of PCDEs. There is only limited information on the presence of PCDEs in the marine environment. High concentrations of PCDEs were found in Baltic white-tailed sea eagles (up to 13 mg/kg lipid weight per congener). Total PCDE concentrations of 50-300 micrograms/kg were reported in cod liver oil samples. PCDEs are immunotoxic and show a clear potency as inducers of hepatic microsomal AHH and EROD activity. Although PCDE concentrations in marine organisms are expected to be lower than those of PCBs, PBDEs, and PCNs, because of their toxic properties, persistence, and hydrophobic and bioaccumulative character and because of the limited information on these concentrations in marine organisms, further research on these concentrations in marine organisms is recommended.

Maternal and developmental toxicity of polychlorinated diphenyl ethers (PCDEs) in Swiss-Webster mice and Sprague-Dawley rats

Polychlorinated diphenyl ethers (PCDEs) are industrial byproducts found in many ecosystems at low levels. PCDEs are not markedly toxic to adult rodents, but their developmental toxicity has not previously been examined. We evaluated the maternal and perinatal toxicity of nine PCDE congeners to outbred mice when compounds were administered from gestation day (GD) 6 through GD 15. 2,2',4,4',5,6'-hexaCDE and 2,3',4',6-tetraCDE decreased the number of pups born per female mated and the number of pups surviving per litter born. 2,2',4,4',5,5'-hexaCDE and 2,2',4,5,6'-pentaCDE decreased the number of litters born per female mated, without decreasing postnatal survival. The other PCDEs did not decrease survival either pre- or postnatally. None of the PCDEs caused absence of Harderian glands in surviving offspring at the doses administered. Neither induction of cytochromes P450 nor tissue residues of individual congeners correlated well with developmental toxicity. Three PCDEs were also evaluated in outbred (Sprague-Dawley) rats: 2,2',4,5,6'-pentaCDE and 2,3',4',6-tetraCDE, because of their toxicity to mice; 2,2',4,4',5,5'-hexaCDE, because it should exhibit PCB-like toxicity. Each congener was administered at three dose levels from GD 6 through GD 15. 2,2',4,5,6'-pentaCDE decreased the number of litters born at 100 mg/kg/day, and the survival of pups in litters carried to term, at both 50 and 100 mg/kg per day. Postnatal weight gain was also reduced. In contrast to its action in mice, 2,3',4',6-tetraCDE decreased neither the numbers of litters born nor postnatal survival of rat offspring, but did suppress postnatal weight gain at least through PD 5. As in mice, induction of cytochromes P450 was not well correlated with the developmental toxicity of individual congeners.

Tissue distribution metabolism and excretion of 2,2',4,4',5-pentachlorodiphenyl ether in the rat

The tissue distribution, metabolism and excretion of 14C-2,2',4,4',5-pentachlorodiphenyl ether (PCDE) were studied in the rat. Radioactivity was distributed in all tissues examined, with the highest concentrations being found in the fat followed by the skin, liver, kidney and muscle. Most of the radioactivity found in the tissues was due to unchanged PCDE. Decay of PCDE in the blood was fitted to a four-compartment pharmacokinetic model, and the last compartment had a half-life of 5.8 days. A total of 55% and 1.3% of an orally administered dose was excreted in feces and urine, respectively, in 7 days. More than 64% of the fecal radioactivity was due to unchanged PCDE, while hydroxylated PCDE accounted for 23%.

Chemical changes of organic compounds in chlorinated water. XIII. Gas chromatographic-mass spectrometric studies of the reactions of Irgasan DP 300 [5-chloro-2-(2,4-dichlorophenoxy)phenol] with chlorine in dilute aqueous solution

The reactions of Irgasan DP 300 with chlorine in water were investigated by means of gas chromatography (GC) and GC-mass spectrometry. Irgasan DP 300 was shown to produce dichloro- and trichloro-2-(2,4-dichlorophenoxy)phenols in chlorine-treated water, followed by the decomposition of these intermediates to chlorophenols. No polychlorinated dibenzo-p-dioxins were detected in chlorine-treated Irgasan DP 300 solutions. The production of some of these compounds is dependent on the number of equivalents of chlorine per mol of compound and on the reaction pH.

Induction of rat hepatic monooxygenase activity by polychlorinated diphenyl ethers

Polychlorinated diphenyl ethers are recognized environmental contaminants. Twelve of these compounds were tested for their ability to induce liver cytochrome P-450 and monooxygenase activities in Sprague-Dawley rats. All the compounds increased P-450 levels or increased monooxygenase activities in a manner resembling 3-methylcholanthrene, phenobarbital or a combination of both (mixed). The responses obtained resembled those of the polychlorinated biphenyls, some of which are known to be toxic.

Study of chlorinated diphenyl ethers and chlorinated 2-phenoxyphenols as interferences in the determination of chlorinated dibenzo-p-dioxins and chlorinated dibenzo furans in biological samples

Two classes of environmentally occurring chlorinated aromatic hydrocarbons which have mass spectral properties similar to the chlorinated dibenzo-p-dioxins (dioxins) and chlorinated dibenzofurans (furans) were studied. Standards of chlorinated diphenyl ethers (CDEs), and chlorinated 2-phenoxyphenols (CPPs) and their methyl ethers, along with the dioxins and furans were passed in steps through a simple method for the analysis of the latter compounds in biological samples. The CDEs, which interfere with the determination of furans by mass spectrometry, had similar extraction, high-performance liquid chromatographic and gas chromatographic properties as the furans but, in all cases studied, were well separated from them on an activated Florisil column using combinations of hexane and dichloromethane as eluting solvents. The higher CPPs on the other hand tended to generate dioxin residues by ring closure when exposed to strong hydrochloric acid solution during sample preparation. In addition, their methyl ethers containing four to six chlorines tracked completely through all stages of the method with the dioxins. Thus, if the methyl ethers of CPPs were present in a sample extract, additional mass spectral information would be needed to further differentiate them from dioxins in environmental samples.

The acute toxicity of penta-, hexa-, and heptachlorohydroxydiphenyl ethers in mice

The acute intraperitoneal LD50 values of various hydroxychlorodiphenyl ethers (HO-ClX-DPEs; X = 5-7) in mice have been determined. The acute toxicities observed were on the order of, or slightly less than, that observed previously for 2-hydroxy-2',4,4'-trichlorodiphenyl ether (2-HO-Cl3-DPE; Irgasan DP-300; Triclosan), a commonly used bactericide. However, the acute toxicities determined for these compounds were substantially less than have been observed for HO-Cl9-DPEs and pentachlorophenol. The HO-ClX-DPEs had a marked hypothermic effect, similar to that produced by 2-HO-Cl3-DPE. Symptomatology following exposure to the HO-ClX-DPEs (X = 5-7) suggested a nonspecific depressant effect on the central nervous system.

A method for the determination of octa- and nonachloro-2-phenoxyphenols in chicken tissue

A gas-liquid chromatographic method was developed capable of determining octa- and nonachloro-2-phenoxyphenols in chicken liver or muscle at 0.25 ppb and fat at 2.5 ppb. The method involves extraction with acidified acetone:hexane, cleanup with concentrated H2SO4 and Florisil column chromatography, methylation with diazomethane, and quantitation by capillary column gas-liquid chromatography with electron capture detection. Fortification of liver and muscle at 0.25 or 0.5 ppb and fat at 2.5 or 5.0 ppb and subsequent analysis yielded recoveries averaging 91% for octa- and 97% for nonachlorophenoxyphenol.

The acute toxicity of nonachloropredioxin and 3- and 4-hydroxynonachlorodiphenyl ether in mice

The acute intraperitoneal LD50 values of hydroxynonachlorodiphenyl ethers (HO-Cl9-DPEs) in mice have been determined. The acute toxicity of each of these compounds is compared with that of pentachlorophenol (PCP) and 2-hydroxy-2',4,4'-trichlorodiphenyl ether (2-HO-Cl3-DPE; Irgasan DP-300; Triclosan), a commonly used bactericide. The order of acute toxicity observed was: 2-HO-Cl9-DPE greater than technical PCP approximately equal to pure PCP greater than 3-HO-Cl9-DPE greater than 4-HO-Cl9-DPE greater than 2-HO-Cl3-DPE. Symptomatology following exposure to the HO-Cl9-DPEs was similar to that observed for PCP, a known uncoupler of oxidative phosphorylation. 2-HO-Cl3-DPE, however, produced clinical signs suggestive of a suppressive effect on the central nervous system. Data on time response following a lethal dose of each of these compounds was also obtained.

Effect of hydroxychlorodiphenyl ethers (chlorinated pre-and isopredioxins) on erythrocyte membrane adenosinetriphosphatase activity

The effect of hydroxychlorodiphenyl ethers (HO-ClX-DPEs; chlorinated pre- and isopredibenzodioxins), contaminants of technical chlorophenol preparations, on human erythrocyte membrane-bound adenosinetriphosphatases (ATPases) has been investigated. Both 2- and 3-HO-Cl9-DPE inhibited the Na+ + K+-activated, Mg2+-dependent ATPase (Na+, K+, Mg2+-ATPase). The Mg2+-dependent ATPase (Mg2+-ATPase) was stimulated at lower concentration of these compounds, but at higher concentrations there was a gradual decrease in the extent of stimulation, 2-Hydroxy-21, 41, 41-trichlorodiphenyl ether (2-HO-Cl3-DPE; Irgasan DP-300; Triclosan) was not as effective as the nonachloro compounds at inhibiting Na+, K+, Mg2+-ATPase and was inactive at stimulating Mg2+-ATPase. Pure pentachlorophenol (PCP) caused both inhibition of Na+, K+, Mg2+-ATPase and stimulation of Mg2+-ATPase, although each effect required a higher concentration of PCP than was needed for the HO-CL9-DPEs. The possible relationship of the effects of HO-CL x-DPEs on human erythrocyte membrane ATPase activities to the potent hemolytic activity of these compounds is discussed.

Induction of xenobiotic metabolism in rat liver by chlorinated biphenyl ether isomers

Chlorinated diphenyl ether isomers were administered to rats at doses of 10 mumols/kg/day po for 3 days. Decachlorodiphenyl ether caused increases in EPN detoxification, NADPH cytochrome c reductase and cytochrome P-450 but did not alter aryl hydrocarbon hydroxylase (AHH). It caused a shift in P450 absorption to 448 nm. 2,4,5,2',4'-Pentachlorodiphenyl ether increased EPN detoxification and cytochrome P-450. 2,4,5,3',4'-Pentachlorodiphenyl ether increased AHH and cytochrome P-450 and caused a shift in the absorption maximum to 448 nm. 3,4,2',4'-Tetrachlorodiphenyl ether induced AHH. 2,4'-Dichlorodiphenyl ether, 4,4'-dichlorodiphenyl ether, 2,4,2'-trichlorodiphenyl ether, 2,4,4'-trichlorodiphenyl ether, 3,4,2'-trichlorodiphenyl ether and 3,4,2',4'-tetrachlorodiphenyl ether did not alter any of these parameters. The position and degree of chlorination are important in determining the extent of induction and pathways induced.

Methane-oxygen enhanced negative ion mass spectra of polychlorinated diphenyl ethers

Methane-oxygen enhanced negative ion mass spectra of 15 chlorinated diphenyl ethers contained some combination of [M-]-., [M-1]-, [M-19]-, [M-36]-, [M-55]-, and [M+35]- anions. The relative abundances of these ions are related to the chlorine substitution pattern. Similar ions appear in the negative ion spectra of polychlorinated anisoles. The study of known isomers of polychlorinated model compounds extends the utility of the negative ion method in the analysis of polychlorinated aromatics such as polychlorinated biphenyls, dioxins and furans. The spectra were shown to be very dependent on the temperature of the ion source; a temperature change of 25 degrees C was shown to have pronounced effects. Spectral variation with temperature has implications for computer library searches, ultimate sensitivity limits and analysis in the presence of interfering isobaric ions.

Metabolism of chlorodiphenyl ethers and Irgasan DP 300

1. In the rat chlorodiphenyl ethers are metabolized via two routes. The predominant reaction is aromatic hydroxylation; scission of the ether bond is a minor metabolic process. 2. In all cases, primary hydroxylation takes place ortho and meta to the ether bond. Ortho-hydroxylation leads to the formation of 'predioxins' in cases where the parent compounds contain a chlorine atom in one of the ortho positions in the second ring. 3. 5-Chloro-2-(2,4--dichlorophenoxy)phenol (Irgasan DP 300), a compound that meets the structural requirements of a predioxin, did not yield chlorodibenzo-p-dioxins or hydroxylated derivatives thereof. 4. Irgasan DP 300 is excreted unchanged in faeces and urine (partly conjugated) but is also hydroxylated to five different monohydroxy metabolites which were found in urine; three of these were also present in faeces. As a result of scission of the ether bond 2,4-dichlorophenol occurred in urine and faeces, and 4-chlorocatechol in urine. 5. Neither in the case of Irgasan DP 300, nor in that of chlorodiphenyl ethers with an ortho chlorine atom, could metabolic cyclization to chlorodibenzofurans or their hydroxylated derivatives be detected.

Identification of hydroxylated chlorodibenzo-p-dioxins, chlorodibenzofurans, chlorodiphenyl ethers and chloronaphthalenes as their methyl ethers by gas chromatography mass spectrometry

The methyl ethers of a number of hydroxylated (poly)chlorodibenzo-p-dioxins, chlorodibenzofurans, chlorodiphenyl ethers and chloronaphthalenes, representing all different hydroxy substitutions, were synthesized and their mass spectra investigated. With the exception of the methoxy derivatives of the chlorodibenzofurans, it appeared that the mass fragmentation patterns of the structural isomers of each class of compounds were very specific and allowed unambiguous assignment of the position of the methoxy group in the molecule. The different fragmentation patterns can be explained in terms of plausible mechanisms resulting in stable charge delocalized (oxonium) ions. Because of its diagnostic value, this method is useful in the structure elucidation of hydroxylated metabolites of pure isomers of chlorodibenzo-p-dioxins, chlorodiphenyl ethers and chloronaphthalenes.

Disturbance of microsomal detoxication mechanisms in liver by chlorophenol pesticides

The pesticide pentachlorophenol known as an uncoupler of mitochondrial oxidative phosphorylation was shown to disturb liver microsomal detoxication functions by a selective inhibition of the terminal oxygenation enzyme P-450. At lower concentrations the flavin moiety of this enzyme chain is not inhibited but rather is stimulated, whereby a qualitative shift in detoxication of aromatic amines from C-oxygenation to N-oxygenation is obtained. The effects were due to the pentachlorophenol itself and not to a metabolite. Similar effects of varying strength were also obtained with other chlorophenol pesticides; 2,4,di-, 2,4,6,-tri and 2,3,4,6-tetrachlorophenol, di- and hexachlorophen, tri- and nonachloro-2-hydroxydiphenyl ethers. The relevance of these findings to the possible synergistic influence of chlorophenols on the carcinogenic effects of polyaromatic amines and hydrocarbons is discussed.

Analysis of polychlorinated dibenzo-p-dioxins and dibenzofurans in chlorinated phenols by mass fragmentography

A rapid, highly specific method for the analysis of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in pentachlorophenol and other chlorinated phenols is described. The rapid sample preparation procedure includes an alkaline extraction of phenolic compounds and chromatography of the neutral substances on an alumina micro-column. After gas chromatographic separation, individual polychlorinated dibenzo-p-dioxins and dibenzofurans are detected and quantified by mass fragmentography. The sample purification procedure removes polychlorinated diphenyl ethers, polychlorinated biphenyls and benzenes, phthalates and polychlorinated phenoxyphenols (predioxins), which might otherwise severely interfere in the analysis. Significant levels of hexa-, hepta- and octachlorodibenzo-p-dioxin and of hexa-, hepta- and octachlorodibenzofuran were found in two commercial products.