Supercritical fluid extraction of polycyclic aromatic hydrocarbons from marine sediments and soil samples.

Supercritical fluid extraction (SFE) was used to extract polycyclic aromatic hydrocarbons (PAH) from a certified sample of marine sediment. This sample contains a great number of organic pollutants that are present in low concentrations. The extractions were carried out at 50 and 80 degrees C, at a pressure varying from 230 to 600 bar and using CO2 in the supercritical phase and the effect of three organic modifiers (methanol, n-hexane and toluene), added at 5%/vol, at the same temperature and pressure conditions, were then considered. PAHs were characterized by GC-MS and the recover yield was estimated for 6 PAHs that were representative of those present in the sample, according to their molecular weight and to the number of condensed rings. The analytical conditions giving the best recovery efficiency were used on an unpolluted soil sample spiked with 11 PAHs of environmental importance at a concentration similar to that certified for the sediment sample. An increase in the yield of recovered PAHs, using methanol as co-solvent, was observed while higher temperatures caused a negative effect on the quantity of recovered pollutants. The recovery yield for PAHs from the spiked soil sample was measured and found to be greater than 90%. Better recoveries were obtained for those compounds with higher molecular weight.

Dioxin contamination in food. Bayreuth, Germany, from September 28 to October 1, 2000.

Dioxin and PCB monitoring programs for food and feeding stuff in most countries of the world, including many European Countries are currently inadequate. Better control of food production lines and food processing procedures is needed to minimize entry of dioxin to the food chain and will help to avoid dioxin contamination accidents. This would also improve the ability to trace back a possible contamination to its source. European guidelines for monitoring programs should be established to ensure comparable and meaningful results. These guidelines should define the minimum requirements for the design of monitoring programs, analytical methods, and quality assurance. Though data from Northern Europe shows that the general population exposure to dioxin and PCB has decreased during the last ten years these compounds continue to be a risk of accidental contamination of the food chain. The most prominent recent example is the Belgian dioxin contamination of feeding stuff in 1999. The Belgian dioxin contamination was not detected due to dioxin monitoring programs but by their direct biological effects seen in animals. Four other cases of dioxin contamination have been detected in Europe since 1997 due to local monitoring programs. One of them (citrus pulp pellets 1998) was in a much larger scale than the Belgian dioxin contamination. The general population's exposure to dioxins and PCBs is still in the same range (1-4 pg WHO-TEQ/kg body weight and day) as the recently revised WHO tolerable daily intake (TDI). There is concern that short-term high level exposure to dioxins, furans, and PCB may cause biological effects on the human fetal development and further research is required. Further actions to control sources building on considerable advances already made in many countries may need to be supplemented by measures to prevent direct contamination of feeding stuff or food to reduce general population exposure further.

Levels of selected organic compounds in materials for candle production and human exposure to candle emissions.

Polychlorinated dibenzo-p-dioxins (PCDD), dibenzofurans (PCDF) selected chlorinated pesticides, polycyclic aromatic hydrocarbons (PAH) and some volatile organic compounds (VOC) were analysed in the exhaust fumes of candles made from different waxes and finishing materials. To guarantee defined burning conditions a chamber was developed for the sampling of the exhaust fumes. Using a simple exposure model, the inhalative uptake of PCDD/PCDF by an adult person was calculated for different scenarios. It was shown that additional uptake of PCDD/PCDF caused by candle emissions does not contribute significantly to the total daily intake of these compounds. Emissions of PCDD/PCDF, benzo(a)pyrene and the VOC were then compared to limit value for working places. Even when many candles would be burnt at the same time in a small room, concentrations of the compounds investigated stay below 1% of the tolerable limit values.

Accumulation of organic air constituents by plant surfaces. Spruce needles for monitoring airborne chlorinated hydrocarbons.

The needles of the spruce (Picea abies) were used to monitor ambient air for organic trace substances. Analyses of spruce needles in an industrialized area demonstrated that the concentrations of these substances were much higher than those in a nonindustrialized area.

Applications of the in vitro aryl hydrocarbon hydroxylase induction assay for determining "2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents": pyrolyzed brominated flame retardants.

The pyrolysis of brominated flame retardants FR 300 BA (decabromobiphenyl) ether, FireMaster BP-6 (polybrominated biphenyls), Bromkal 70-5-DE (primarily pentabromodiphenylether), Bromkal 70-DE (primarily penta and tetrabromodiphenylether) and Bromkal G1 (pentabromodiphenylether) resulted in the formation of relatively high levels of polybrominated dibenzofurans (PBDFs) and dibenzo-p-dioxins (PBDDs as determined by gas chromatography-mass spectrometric analysis. The dose response EC50 values for the induction of aryl hydrocarbon hydroxylase (AHH) and ethoxyresorufin O-deethylase (EROD) by the flame retardant pyrolysates was determined in rat hepatoma H-4-II E cells and compared to the relative induction activities of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and the concentrations of "2,3,7,8-TCDD equivalents" were calculated. The range of "2,3,7,8-TCDD equivalents" levels (micrograms/g or ppm) derived from values obtained from the AHH and EROD bioassays for each of the pyrolyzed flame retardant samples was: 174-194, 480-1400, 2140-4680, 6740-8780 and 3920-5260 ppm for FR 300 BA, FireMaster BP-6, Bromkal 70 DE, Bromkal 70-5 DE and Bromkal G1, respectively. The in vivo dose-response effects of 2 pyrolyzed flame retardants were determined in immature male Wistar rats and compared to the dose-response activities of 2,3,7,8-TCDD. The in vivo responses which were measured included hepatic microsomal AHH and EROD induction, body weight loss and thymic atrophy. For the pyrolyzed FireMaster BP-6 and Bromkal 70-5 DE samples, the range of calculated in vivo "2,3,7,8-TCDD equivalents" (ppm in sample) for the 4 in vivo bioassays was 520-1780 ppm and 3860-8960 ppm, respectively. The excellent overlap between the in vivo and in vitro 2,3,7,8-TCDD equivalents for the 2 flame retardant pyrolysate extracts supports the utility of the in vitro induction bioassay for quantitatively determining "2,3,7,8-TCDD equivalents" for mixtures containing toxic halogenated aryl hydrocarbons.

Differences between retentions of various classes of aromatic hydrocarbons in reversed-phase high-performance liquid chromatography. Implications of using retention data for characterizing hydrophobicity.

Capacity factors of a series of alkylbenzenes (C1-C10), 12 chlorobenzenes, 9 chlorotoluenes, 17 chloronaphthalenes and 65 chlorobiphenyls have been measured on an octadecylsilica column. Aqueous methanol of four different compositions (80-95% methanol) was used as eluent. Logarithms of capacity factors of all eluites are linearly related to the amount of organic modifier in the eluent. In addition, linear relationships between the solvent strength and the logarithms of capacity factors extrapolated to zero methanol have been revealed. The proportionality factors are dependent on the structures of the eluites. Thermodynamic consideration of the retention processes shows that, within each type of eluite, enthalpy-entropy compensation is found. The compensation temperatures are not significantly different for the various types of eluite. Furthermore, it is shown that the compensation temperatures increase with increasing water content of the eluent. Since the intercepts of the delta G0-delta H0 plots are not equal for the various types of eluite, it was concluded that the distribution processes causing retention of benzene, naphthalene and biphenyl are different. When only the free energies of retention (i.e. the capacity factors) of different types of eluite are compared, no accurate information on the hydrophobicity of the eluites can be obtained if aqueous methanol is used as eluent. Therefore the possibilities for relating or predicting other physico-chemical parameters of the test compounds, such as octan-1-ol-water partition coefficients with isocratic retention data, will be limited.

Formation of polychlorinated dibenzofurans and dioxins during combustion, electrical equipment fires and PCB incineration.

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are likely formed by thermal synthesis of a variety of primary precursors. Highest levels of these compounds are expected, however, when the starting material requires only one or two reaction steps for their formation, as is the case with chlorophenols, chlorobenzenes and polychlorinated biphenyls (PCBs). Laboratory pyrolyses have indeed shown that PCBs give significant yields of PCDFs, and chlorobenzenes give both PCDFs and PCDDs. In addition, a variety of other chloroaromatic compounds are formed. From these experiments and from accidents involving PCB fires, it is known that PCDFs are the most important toxic compounds associated with PCBs. Most commercial PCBs contain PCDFs in the low ppm range. PCDF concentration does not increase during normal operation in electrical equipment. Accidents (fires and explosions) involving PCBs can give PCDF levels in soot of up to 1000 ppm and higher. Effective thermal destruction of PCB is possible in modern incineration units, provided high temperatures, excess air and sufficient residence times are used. Exact figures for minimum temperature and residence time cannot be given, since feedstock and incinerator construction greatly influence destruction efficiency. Effluents from EPA-licensed incinerators used for PCB destruction contain only very low levels of PCDDs and PCDFs.

[Pesticides]. / Pestizide.

This review introduces the most important groups of pesticides. The necessary application of pesticides involves advantages as well as risks for man and environment.

Chemicals, man and the environment: a historic perspective of pollution and related topics.

The interaction of chemicals with biological organisms is as old as life itself. Chemical pollution is usually considered to be human interference with natural chemical cycles and the release of man-made, unnatural compounds. The article traces five areas of chemical pollution and health hazards: air pollution, water pollution, occupational exposure, pollution from agricultural practices and contamination of food. It is suggested that historic perspective can aid in rational and prudent evaluation of present-day pollution problems.

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.

Identification of hydroxyhalobiphenyls as their methyl ethers by gas chromatography mass spectrometry.

The mass spectra and gas chromatographic properties of 17 synthetic fluoro-, chloro- and bromomethoxy-biphenyls and 12 dichlorodimethoxybiphenyls have been examined. From this representative series it appears that the position of the methoxy group (ortho, meta and para to the biphenyl bond) in all monomethoxy compounds examined, and the positions of the two methoxy groups in most of the dimethoxy compounds, can be assigned unambiguously by their difference in fragmentation pattern. The value of this method was shown by metabolism experiments in which 4,4'-difluoro- and 4,4'-dibromobiphenyl were fed to rats and 4,4'-dichlorobiphenyl was administered to plants. All hydroxylated metabolites found were identified by gas chromatography mass spectrometry. Relationships between structure and gas chromatographic retention time of these compounds are discussed.

Reductive dechlorination of chlorobiphenylols by rats.

Dechlorinated products were isolated from the urine of rats that were administered chlorobiphenylols, the primary hydroxylated metabolites of PCB in mammals. The mechanism of chlorine loss from chlorobiphenylols is different from the mechanism of dechlorination via arene oxides whereby concomitant hydroxylation is always observed.

Use of ethyl ethers, deuteriomethyl ethers and cyclic n-butylboronates of hydroxychlorobiphenyls in identification of metabolites of polychlorinated biphenyls.

The mass spectra and gas chromatographic properties of a number of chlorobiphenylols, chlorobiphenyldiols, chlorophenols and naphthols, as well as their methyl, deuteriomethyl and ethyl ethers and some cyclic n-butylboronates have been investigated. Metabolism experiments with 4'-chloro-4-biphenylol showed that the selective use of ethylation and methylation is most effective in both detection and structure elucidation of metabolites partly methylated by metabolic processes. The usefulness of deuteriomethylation in such studies seems to be limited. The formation of cyclic n-butylboronates provides specific information on o-dihydroxy derivatives of chlorobiphenyls.