Dangerous chemicals

Council Regulation (EEC) No 2455/92 has been adopted by the Council of the European Communities, in 1992, to improve information exchange on certain dangerous chemicals with third countries, particularly developing countries. To implement the notification procedure in accordance with the Regulation, a database has been developed to manage and simplify the procedure. The software exists in three versions; one adapted for use by the Designated Authorities of the Member States, another for the European Chemicals Bureau (ECB) and the third one is an information version aimed at Designated National Authorities outside the European Union and Industry. The database “EDEXIM” is currently working in a PC environment and is being developed as an on-line system with a stand-alone client/server architecture.     

Ecochemical assessment of environmental chemicals Part I: Standard screening procedure to evaluate chemicals in plant cell cultures

A standard screening procedure using sterile soybean and wheat cell suspension cultures has been developed to study the metabolic profiles of established xenobiotics as well as new synthesized compounds. This short term test provides quantitative data on the distribution of metabolites and the parent compound between the nutrient medium and the plant cells, on the amount of more and less polare metabolite fractions in comparison to the parent compound and the amount of substance bound or irreversibly absorbed to the extracted cell fragments. From this data turnover rates are calculated for ranking purpose. Results obtained for 2,4-D, PCP, DEHP and monolinuron as model substances are presented and compared with data from other environmental tests.     

Opportunities for a probabilistic risk assessment of chemicals in the European Union

In risk assessment of new and existing substances, it is current practice to characterise risk using a deterministic quotient of the exposure concentration, or the dose, and a no-effect level. A sense of uncertainty is tackled by introducing worst-case assumptions in the methodology. Since this procedure leads to an assessment with an unknown degree of conservatism, it is advisable to deal quantitatively with uncertainties. This paper discusses the advantages and possibilities of a probabilistic risk assessment framework, illustrated with an example calculation. Furthermore, representatives of EU Member States and the chemical industry were interviewed to find out their views on applying uncertainty analysis to risk assessment of industrial chemicals.     

The efficiency of two standardized procedures for extracting mutagenic chemicals from soils

A major technical limitation to monitoring the fate of mutagenic compounds in soil is the lack of an established extraction procedure. This study was conducted to evaluate the efficiency of the blender extraction procedure for extracting benzo(a)pyrene (BAP) or 2-nitrofluorene (2NF) from a Weswood silt loam or a Bastrop clay loam soil. Extracted residues were evaluated using the Salmonella/microsome mutagenicity assay and high performance liquid chromatography (HPLC) to quantify recovery of the two chemicals from soil. In addition, a limited study using only the mutagenicity assay was conducted to compare the efficiency of the Blender and Soxhlet extraction procedures for recovering organic mutagens from both soils amended with a wood preserving bottom sediment waste.Extracted residues were dissolved in dimethylsulfoxide to concentrations that could be detected in the bioassay. Over all treatment levels and for both soils, the extraction efficiency of the blender procedure for BAP was greater than 80% for 12 of 16 treatments as measured using both bioassay and HPLC analysis; while, for 2NF the extraction efficiency was greater than 90% for all 15 treatments as measured by HPLC, and greater than 80% for twelve of 15 treatments as measured by bioassay. These results indicate that blender extraction provided efficient recovery of the pure compounds tested. When the efficiency of the blender and Soxhlet procedure for extracting the wood-preserving bottom sediment and waste amended soil were compared, significantly greater levels of mutagenic activity were detected in the fractions extracted using the blender extraction than were detected using the Soxhlet extraction.     

Data ranges in aquatic toxicity of chemicals

A significant problem for effect assessment of aquatic ecosystems arises from the large ranges of toxicity data, which can be found in different databases and literature. Here, ranges are given for the aquatic toxicity of 27 high production volume chemicals. Based on these illustrative examples and on the current literature on uncertainty in aquatic effect assessment, toxicity ranges are discussed for their possible causes (variation in experimental condition, species, endpoint, time) and ways to handle them (safety factors). Implications and recommendations on the procedure of risk analysis of chemical substances are drawn. Two main requirements for a comprehensive risk assessment are identified, which often play a minor role in current practice (as they are often neglected) as well as in scientific discussion (as they are meant to be trivial). First, data quality must be checked critically before applying any result of a toxicity test. Secondly, experimental data should take into account different species and acute as well as chronic data. If these aspects are considered in risk analysis, which is common practice in ecotoxicology but not always in the context of practical applications in risk engineering, a more comprehensive picture of the environmental toxicity of a chemical substance can be obtained.     

Triglyceride / phospholipid partitioning and persistence of environmental chemicals

An isopycnic centrifugation procedure has been developed in order to determine the solubility and partitioning of chemicals in hydrated egg lecithin and triolein. The following environmental chemicals have been studied, DDT, DDE, PCBs, 2, 4-D, lindane and dieldrin.Between 5 and 100 moles of these chemicals were dissolved per 100 moles of lipid, and solubility in triolein was between 1,5 and 5-fold higher than in hydrated egg lecithin.The following partition coefficients for distribution between triolein and hydrated egg lecithin were obtained, 9.8 for DDE, 9.0 for DDT, 5.9 for the PCBs, 3.2 for dieldrin and 2.7 for lindane. A more polar metabolite of DDT, DDA, had a partition coefficient of 0.09. The non-persistent herbicide, 2,4-D, showed no detectable association with triolein.The observed preferential association with triglyceride rather than lipophilicity itself is concluded to be a major reason for the persistence of certain environmental chemicals.     

Determination of wavelength-averaged,near UV quantum yields for environmental chemicals

The present study describes a procedure for determination of an average quantum yield for the wavelength range of 310 to 410 nm. Solutions of the pollutant in sealed Pyrex tubes are irradiated in a Rayonet photoreactor fitted with fluorescent lamps emitting maximally at 355 nm. The integrated spectral overlap and the photolysis half-life for both the chemical actinometer and the pollutant are determined and from these data the quantum yield is calculated. The method has been evaluated by measuring quantum yields for organophosphorus, chlorinated hydrocarbon, and dinitroaniline pesticides and $\text{p}$-nitroanisole/pyridine mixtures. Corrected quantum yields are obtained on simultaneous irradiation of the trifluralin actinometer.     

Mechanism of concentration addition toxicity: they are different for nonpolar narcotic chemicals, polar narcotic chemicals and reactive chemicals

According to the toxicity mechanism of the individual chemicals, the concentration addition toxicity mechanism is revealed for nonpolar-narcotic-chemical mixtures, polar-narcotic-chemical mixtures and reactive-chemical mixtures, respectively. For nonpolar-narcotic-chemical mixtures, the partitioning of individual chemicals from water to biophase was determined, and the result shows that their concentration additive effect results from no competitive partitioning among individual chemicals. For polar-narcotic-chemical mixtures, their toxicity are contributed by two factors (the total baseline toxicity and the hydrogen bond donor activity of individual chemicals), and it is the concentration additive effect for either of these two factors that leads to their concentration addition toxicity. In addition, the interactions between the reactive chemicals and the biological macromolecules are discussed thoroughly. The results suggest that the net effect of these interactions is zero, and it is this zero net effect that leads to the concentration addition toxicity mechanism for reactive-chemical mixtures.     

Improvement of an efficient separation method for chemicals in diesel exhaust particles: analysis for nitrophenols

GOAL, SCOPE, AND BACKGROUND: Diesel exhaust is believed to consist of thousands of organic constituents and is a major cause of urban pollution. We recently reported that a systematic separation procedure involving successive solvent extractions, followed by repeated column chromatography, resulted in the isolation of vasodilatory active nitrophenols. These findings indicated that the estimation of the amount of nitrophenols in the environment is important to evaluate their effect on human health. The isolation procedure, however, involved successive solvent extractions followed by tedious, repeated chromatography, resulting in poor fractionation and in a significant loss of accuracy and reliability. Therefore, it was crucial to develop an alternative, efficient, and reliable analytical method. Here, we describe a facile and efficient acid-base extraction procedure for the analysis of nitrophenols. MATERIALS AND METHODS: Diesel exhaust particles (DEP) were collected from the exhaust of a 4JB1-type engine (ISUZU Automobile Co., Tokyo, Japan). Gas chromatography-mass spectrometry (GC-MS) analysis was performed with a GCMS-QP2010 instrument (Shimadzu, Kyoto, Japan). RESULTS: A solution of DEP in 1-butanol was extracted with aqueous NaOH to afford a nitrophenol-rich oily extract. The resulting oil was methylated with trimethylsilyldiazomethane and subsequently subjected to GC-MS analysis, revealing that 4-nitrophenol, 3-methyl-4-nitrophenol, 2-methyl-4-nitrophenol, and 4-nitro-3-phenylphenol were present in significantly higher concentrations than those reported previously. DISCUSSION: Simple acid-base extraction followed by the direct analysis of the resulting extract by GC-MS gave only broad peaks of nitrophenols with a poor detection limit, while the GC-MS analysis of the sample pretreated with (trimethylsilyl)diazomethane gave satisfactorily clear chromatograms with sharp peaks and with a significantly lowered detection limit (0.5 ng/ml, approximately 100 times). CONCLUSION: The present method involving an acid-base extraction, in situ derivatization, and GC-MS analysis has shown to be a simple, efficient, and reliable method for the isolation and identification of the chemical substances in DEP.     

Methodologies for evaluating sources of volatile organic chemicals (VOC) in homes

After a classification of sources of VOC into four groups (continuous and intermittent, regular and irregular) and of air sampling procedures according to the duration of sampling and the sampling mode (active and passive), three representative case-studies are presented to discuss how an appropriate combination of source-type and sampling procedure can lead to a source evaluation. One of the case-studies revealed that the results of emission rate measurements carried out in the laboratory can give erroneous predictions of the substance concentrations to be expected in practice. It is concluded that evaluating sources of VOC under general toxicological and public health aspects calls for an intensive statistical treatment of measurements and questionnaires obtained from a very large number of homes.     

Review of strobilurin fungicide chemicals

Strobilurins are natural products isolated and identified from specific fungi. Natural strobilurins were named in the order of their discovery as strobilurin-A followed by strobilurin-B, C, D etc. Their discovery opened the door for new chemistry of synthetic fungicides. Applying Quantitative Structural Activity Relationship (QSAR) on the structures of the natural strobilurins, many pesticide companies were able to discover many synthetic analogues that are more efficacious and more stable fungicides. At present there are about eight synthetic strobilurins in the fungicides worldwide market. Some of these products are worldwide registered for use as agrochemical and some are in the process of registration. This class of fungicides is relatively new, as crop protection products and information about them is still fairly scarce. In this review, syntheses and chemistry of natural and synthetic strobilurins are discussed. Also, the mode of action, efficacy, biotic/abiotic degradation, analytical methods, and agricultural uses are discussed.     

Review of strobilurin fungicide chemicals

Strobilurins are natural products isolated and identified from specific fungi. Natural strobilurins were named in the order of their discovery as strobilurin-A followed by strobilurin-B, C, D etc. Their discovery opened the door for new chemistry of synthetic fungicides. Applying Quantitative Structural Activity Relationship (QSAR) on the structures of the natural strobilurins, many pesticide companies were able to discover many synthetic analogues that are more efficacious and more stable fungicides. At present there are about eight synthetic strobilurins in the fungicides worldwide market. Some of these products are worldwide registered for use as agrochemical and some are in the process of registration. This class of fungicides is relatively new, as crop protection products and information about them is still fairly scarce. In this review, syntheses and chemistry of natural and synthetic strobilurins are discussed. Also, the mode of action, efficacy, biotic/abiotic degradation, analytical methods, and agricultural uses are discussed.     

Laboratory simulation of biodegradation of chemicals in surface waters: closed bottle and respirometric test

Microbial degradation is the most dominant elimination mechanism of organics from the environment. For evaluation of biodegradability of pure chemicals many standardized tests are available, but no standardized procedure for assessment of biodegradability of chemicals in surface water is agreed upon. Rates of in-situ biodegradation are usually estimated in laboratory simulation where environmental factors are reproduced to some extent. The aim of our study was to compare standardised ready biodegradability assessment, test (Closed bottle test) and its modifications employing the basic agreements on test conditions to simulate biodegradation in surface water. Standard test was modified using various natural river waters to simulate the natural environment in a simplified way. The impact of different types and amounts of nutrients and microorganisms on biodegradation was confirmed. The conditions in the recipient should be examined to extrapolate the results from ready biodegradability tests to real surface water.     

Sorption kinetics of chlorinated hydrophobic organic chemicals

This is the second of a two-part series describing the sorption kinetics of hydrophobic organic chemicals. Part I “The Use of First-Order Kinetic Multi-Compartment Models” is published in issue 1 of this journal, pp. 21–28. Sorption kinetics of chlorinated benzenes from a natural lake sediment have been investigated in gas-purge desorption experiments. Biphasic desorption curves, with an initial “fast” part and a subsequent “slow” part, were found for all tested chlorobenzenes. From these results first-order sorption uptake and desorption rate constants were calculated with a two-sediment compartment model, which is presented in the first paper. In three sets of experiments the sorption uptake period and sediment/water ratio were varied. Rate constants are not influenced by these experimental conditions, which supports the partitioning concept for the sorption of hydrophobic organic chemicals in sediments.     

Toxicity testing of highly volatile chemicals with green algae

A gas-tight system for toxicity testing of highly volatile chemicals with the green algaChlamydomonas reinhardtii was developed. The procedure permits maintenance of constant and defined concentrations of the tested compounds in the vessels. To ensure sufficient CO₂-supply, new bipartite test vessels were used. These vessels allowed spatial separation of a HCO₃-/CO ₃ ^2? buffer used for CO₂ supply and the alga culture to avoid growth inhibition due to ionic strength. Several volatile chlorinated hydrocarbons have been tested. Their EC10 values were several orders of magnitude lower than those obtained with open test systems.     

Quantifying the sorption of organic chemicals on sediments

The use of a reference compound to quantify the sorption of nonpolar organic chemicals is proposed. This is because organic carbon normalized sorption coefficients (K_OC) do appear to be dependent on the type of sediment, and are thus not generally applicable to characterize the sorption properties of chemicals. Therefore, in this paper the hypothesis that nonpolar chemicals sorb in a constant ratio, independent of the sediment, has been investigated. Evidence for this hypothesis is shown with data from the literature. This enables one to compare sorption properties of nonpolar compounds on different sediments, if the differences between the sediments are normalized with a reference chemical rather than with the organic carbon content. Sediments with an organic carbon content of less than 0.1% seem to be unsuitable, because the compounds do not sorb mainly on the organic carbon, but also on other parts of the sediment. Sorption coefficients of compounds with aqueous solubilities in the μg per liter range or octan-1-ol water partition coefficients of more than 10⁵ are strongly influenced by the experimental techniques used. For these compounds the sorption coefficients measured by different techniques are less comparable. To enable comparison of sorption coefficients of hydrophobic chemicals, the use of a chlorobenzene as a reference compound in sorption experiments is suggested.     

Fuzzy clustering analysis of the first 10 MEIC chemicals

In this paper, we discuss the classification results of the toxicological responses of 32 in vivo and in vitro test systems to the first 10 MEIC chemicals. In this order we have used different fuzzy clustering algorithms, namely hierarchical fuzzy clustering, hierarchical and horizontal fuzzy characteristics clustering and a new clustering technique, namely fuzzy hierarchical cross-classification. The characteristics clustering technique produces fuzzy partitions of the characteristics (chemicals) involved and thus it is a useful tool for studying the (dis)similarities between different chemicals and for essential chemicals selection. The cross-classification algorithm produces not only a fuzzy partition of the test systems analyzed, but also a fuzzy partition of the considered 10 MEIC (multicentre evaluation of in vitro cytotoxicity) chemicals. In this way it is possible to identify which chemicals are responsible for the similarities or differences observed between different groups of test systems. In another way, there is a specific sensitivity of a chemical for one or more toxicological tests.     

Environmental Hazard- Assessment of chemicals and products

Part II: Persistence and Degradability of Organic Chemicals The criteria “Persistence” and “Degradability” are defined and explained, starting from the “functional” definition of the environment. In this definition, theenvironment is the counterpart of thetechnosphere, which consists of all processes controlled by man. A substance is persistent if there are no sinks (degradation processes). It is shown that persistence is the central and most important critérium of environmental hazard assessment of organic chemicals. It follows that all substances released into the environment should be degradable, preferentially into small inorganic molecules (mineralization). As examples for persistent substances, the polychlorinated biphenyls (PCB), the chlorofluorohydrocarbons (CFC), bis (2-ethylhexyl) phthalate (DEHP), and 2,3,7,8-tetrachloro-dibenzo-dioxin (TCDD) are discussed. Finally, an attempt to quantify persistence is made.     

Some Danish approaches to selection of existing chemicals

A number of Danish projects based on the OECD principles fon selection of existing chemicals are described. Methods of using SAR to predict lacking biological data are proposed, starting from homologous chemical groups. Exposure data is however usually obtained from information related to chemicals from very diverse chemical groups and this presents difficulties in combining exposure and effects data at an early stage in the selection process.