Abstract  National Science Foundation; Ford Motor Company.#The phase in which a toxic semivolatile organic compound (SOC) exists strongly influences its fate in the atmosphere and its potential health impact. Since the late 1970s, gas-particle partitioning theories have been based upon Lang-muirian adsorption, which assumes equilibrium conditions(1-4). For this theory to work, it is necessary that SOCs be able to rapidly "off-gas" from the particles to maintain equilibrium as particles dilute from their sources. To provide insights into the kinetics of mass transfer between the gas and particle phases, evaporation rates of SOCs from particle surfaces are needed. In this study, we investigated the evaporation rates of selected polycyclic aromatic hydrocarbons (PAHs) from fresh diesel soot particles. The approach utilized a large gas-phase stripping device (LGPS) designed to remove gas-phase PAHs over time scales of seconds. This minimized condensation so that evaporation rates could be measured directly. Preliminary data from this study suggest very fast evaporation rates. The possibility also exists for SOC particle off-gassing artifacts inside the sampling denuders. This would occur as SOCs were removed from the gas-phase.

Abstract  Quantitative structure-activity relationship (QSAR) estimates of toxicity of narcotic chemicals for 19 species of bacteria, algae, fungi, protozoans, coelenterates, rotifers, molluscs, crustaceans, insects, fish, and amphibians were used to predict no-effect levels (NELs) at the ecosystem level by means of recently developed extrapolation methods. Equilibrium partitioning theory was used to derive NELs for aquatic sediments and internal toxicant concentrations for aquatic organisms. A simple table is given from which NELs for narcotic chemicals for water, sediment, and residues in biota can be predicted on the basis of only the octanol/water partition coefficient and molecular weight. The method may be applied to setting quality criteria for the aquatic environment and to ecotoxicological interpretation of (bio)monitoring data. Calculations were carried out for 102 narcotic compounds.

Abstract  The composition of exhaust emissions from eight in-service passenger cars powered by liquefied petroleum gas (LPG) and unleaded petrol (ULP) were measured on a chassis dynamometer at two driving speeds (60 and SO km h(-1)) with the aims of evaluating their polycyclic aromatic hydrocarbon (PAH) contents and investigating the effects of the type of fuel on vehicle performance, ambient air quality and associated health risks. Naphthalene, fluorene, phenanthrene, anthracene, pyrene, chrysene, benzo(a)anthracene and benzo(b)fluoranthene were the most prominent PAHs emitted by both ULP and LPG powered cars. The total emission factors of PAHs from LPG cars were generally lower than (but statistically comparable with) those of ULP cars. Similarly, the total BAP(eq) of the PAHs emitted by LPG cars were lower than those from ULP cars. Multi-criteria decision making (MCDM) methods showed that cars powered by LPG fuel performed better than those powered by ULP fuel in term of PAH levels. The implications of these observations on the advantages and disadvantages of using ULP and LPG fuels are discussed. (c) 2006 Elsevier Ltd. All rights reserved.

Abstract  Previous studies have demonstrated the formation of three glutathione conjugates during the hepatic and pulmonary microsomal metabolism of naphthalene in the presence of reduced glutathione and cytosolic enzymes containing the glutathione transferases. These glutathione conjugates now have been identified by negative ion fast atom bombardment mass spectrometry, by proton NMR spectroscopy, and by chemical synthesis from the (1S,2R)- and (1R, 2S)-naphthalene 1,2-oxide enantiomers as isomeric hydroxyglutathionyldihydronaphthalene derivatives. All three glutathione adducts yielded prominent mass spectral ions at m/z 450 (M-H)-, 432 (dehydration product), and 306 (glutathionyl moiety) which were consistent with the monoglutathionyl derivatives of hydroxydihydronaphthalene. Signals in the proton NMR spectra at 3.60 and 4.95 ppm (adduct 1) and 3.60 and 4.95 ppm (adduct 2) indicated that these conjugates were diastereomers of 1-hydroxy-2-glutathionyl-1,2-dihydronaphthalene. Corresponding signals for H1 and H2 at 4.22 and 4.45 ppm for adduct 3 showed that this isomer was generated from attack of glutathione at the 1 position of the naphthalene 1,2-oxide. Incubation of synthetic (1S, 2R)-naphthalene 1,2-oxide with glutathione in the presence of glutathione transferases resulted in the formation of adducts 1 and 3 in approximately equal proportions; under identical conditions, glutathione conjugate 2 was formed from (1R, 2S)-naphthalene 1,2-oxide. Incubation of naphthalene, glutathione, and glutathione transferases with pulmonary, hepatic, or renal microsomal preparations from mouse, rat, and hamster resulted in the formation of all three glutathione conjugates. Substantial differences in the rates of formation of the individual conjugates were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract  BIOSIS COPYRIGHT: BIOL ABS. Soil ventilation is widely used to promote in situ soil bioremediation at leaking underground storage tank sites. Effects of this process on microbial activity, however, are ill-defined. In this study, biodegradation and volatilization of a model fuel hydrocarbon ((14C)naphthalene) in a gasoline-contaminated soil was determined in columns that were either intermittently or continuously ventilated at a low air-flow rate. With continuous ventilation, volatilization was extensive (up to 38.8%) and mineralization relatively minor (10.4%). Intermittent ventilation decreased volatilization ten-fold but also reduced mineralization to negligible levels. Compared to the continuously aerated columns, the intermittently vented soil had significant microbial population reductions, lower CO2 production, and higher residual gasoline. These results indicated that the ineffectiveness of intermittent ventilation for stimulating biodegradation could be attributed to its failure to reduce

Abstract  BIOSIS COPYRIGHT: BIOL ABS. Fume condensates from asphalt and coal tar pitch were evaluated to determine if polycyclic aromatic hydrocarbon (PAH) composition, crude oil source, or temperature at which the fume was generated correlated with mutagenic activity. The fume condensates were tested for mutagenic activity using a modified Ames Test. Benzo(alpha)pyrene (BP) and other PAHs were detected in all samples. The concentration of BP in coal tar pitch was 18,100 ppm while the concentration in asphalt was less than 6 ppm. Coal tar fumes contained between two and three orders of magnitude more BP, as well as other PAH species, than asphalt fumes. Coal tar fume condensates were also approximately 100 times more mutagenic than those of asphalt. Generation temperature, crude oil source, and/or process conditions affected the PAH concentrations but not the mutagenicity in roofing asphalt fume condensates. With paving asphalt fumes, PAH content and mutagenicity varied with crude oil source but not with pr

Abstract  It is proposed that metabolism of several structurally-related chemicals by CYP2F isoforms of the cytochromes P450 family results in a cytotoxicity-driven mode of action in organs high in CYP2F; namely, CYP2F2 in nasal and lung tissue in mice and CYP2F4 in nasal tissues in rats. Importantly, the CYP2F1 isozyme expressed in humans appears to have a low capacity to metabolize these compounds. In mice, the resultant cytotoxicity and subsequent regenerative hyperplasia is hypothesized drive an increase in lung tumors that are mostly benign and are not life shortening. Although a complete picture of the mode of action has not been developed in any one model compound, data from the individual compounds can be combined to synthesize and reinforce confidence in the CYP2F toxicity hypothesis. For coumarin, naphthalene, and styrene, inhibition of toxicity with inhibition of CYP2F2 has been demonstrated. Rat CYP2F4 appears to be equally active in metabolizing these chemicals; however, CYP2F4 occurs to a much lower extent in rat Clara cells and levels of metabolites produced are not sufficient to cause lung cytotoxicity. Human lungs contain far fewer of Clara cells than rats or mice, and human lung microsomes failed to, or only marginally, metabolize these compounds. In addition, the human lung differs markedly from the mouse lung in the morphology of its Clara cells, which make humans much less sensitive than mice to toxicity due to reactive metabolites. The absence of a role for CYP2E1-generated metabolites (primarily alkyl oxidation vs. ring-oxidation) in mouse pulmonary effects was demonstrated by the lack of protection from styrene toxicity by CYP2E1 inhibitor, or reduction of toxicity in CYP2E1-knockout mice, and lack of lung toxicity of the primary metabolite of ethylbenzene. The chemicals used as examples of this mode of action generally are negative in standard genotoxicity assays. Apart from increased SCE, no consistent pattern in genotoxicity results was found among these chemicals. Thus, while lung tumors from bronchiolar cell cytotoxicity are theoretically possible in humans, it is unlikely that metabolism by CYP2F1 would produce levels of cytotoxic metabolites in human lungs sufficient to result in lung cytotoxic responses and thus tumors. Therefore, it is unlikely several chemicals that cause mouse lung tumors via CYP2F2 metabolism will cause lung tumors in humans.

Abstract  Some cytochrome P450 catalyzed reactions show atypical kinetics, and these kinetic processes can be grouped into five categories: activation, autoactivation, partial inhibition, substrate inhibition, and biphasic saturation curves. A two-site model in which the enzyme can bind two substrate molecules simultaneously is presented which can be used to describe all of these observed kinetic properties. Sigmoidal kinetic characteristics were observed for carbamazepine metabolism by CYP3A4 and naphthalene metabolism by CYPs 2B6, 2C8, 2C9, and 3A5 as well as dapsone metabolism by CYP2C9. Naphthalene metabolism by CYP3A4 and naproxen metabolism by CYP2C9 demonstrated nonhyperbolic enzyme kinetics suggestive of a low Km, low Vmax component for the first substrate molecule and a high Km, high Vmax component for the second substrate molecule. 7, 8-Benzoflavone activation of phenanthrene metabolism by CYP3A4 and dapsone activation of flurbiprofen and naproxen metabolism by CYP2C9 were also observed. Furthermore, partial inhibition of 7, 8-benzoflavone metabolism by phenanthrene was observed. These results demonstrate that various P450 isoforms may exhibit atypical enzyme kinetics depending on the substrate(s) employed and that these results may be explained by a model which includes simultaneous binding of two substrate molecules in the active site.

Abstract  PAHs, including naphthalene, fluoranthene and fluorene rapidly induced extracellular Ca2+ influx and hence elevation of intracellular Ca2+ concentration and NO production. The effect can be inhibited by Ca2+ channel blocker but not by P450 inhibitor. In addition to the rapid effect, we have also found that the eNOS mRNA and protein expression were augmented in HUVECs treated with PAHs at concentration as low as 0.1 μM for 24 h. These effects were abolished when the HUVECs were pretreated with the BAPTA, NiCl2 and SKF96365, as well as SKF525A. Our results revealed that, for the first time, PAHs induce the activation of eNOS and enhance eNOS protein expression in HUVECs both in a Ca2+-dependent manner.

Abstract  Tenax-TA adsorbent tubes were used to collect 54 volatile hydrocarbon compounds in the workplace air and detected by thermal desorption-gas chromatography. The results showed that the correlation coefficients of 1,1-dichloroethylene, dichloromethane, 1,2-dichloroethylene (trans), 1,2-dichloroethylene (cis), 2,2-dichloropropane, bromochloromethane, 1,1,1-trichloroethane, 1,2-dichloroethane, and 1,1-dichloropropene were between 0.9941 and 0.9986, and the detection limits of bromochloromethane, dibromomethane, trichloromethane, bromodichloromethane, 2,2-dichloropropane, dibromochloromethane, and bromoform were 5.4 to 10.3 ng, and the minimum detection concentration was 0.01 to 0.1 mg/m³ (sampling volume 0.5 L). The correlation coefficients of the remaining 38 volatile hydrocarbons were all greater than 0.999, and the minimum detection concentration was 0.001-0.01 mg/m³; the detection limits of olefins were 0.4-2.7 ng, alkanes were 1.4-3.7 ng, aromatic hydrocarbons were 0.2-1.0 ng, and naphthalene was 2.2 ng; the thermal desorption efficiencies of 54 volatile hydrocarbons were 92.1%-113.1%, and the RSDs were 0.6%-17.4%. The RSD values ​​of -trichloroethane, 1,1-dichloroethylene, 2,2-dichloropropane, trichloromethane, 1,2-dichloroethylene (trans), dichloromethane, and bromochloromethane were between 5.1% and 17.4%, while the RSDs of the other 45 volatile hydrocarbons were all less than 5%; the penetration capacity of 9 compounds was 400-4000 ng, and the penetration capacity of the other compounds was greater than 10000 ng; in the stability experiment, except for 2,2-dichloropropane and bromodichloromethane, the loss rate within 15 days was 10%-15%, and the loss rate of the other 52 compounds was less than 5%. This method can be used for the detection of volatile hydrocarbons in the workplace air, and it is fast and accurate.

Abstract  The effects of ethylene on permeability and RNA and protein synthesis were assayed over a 6 to 26 hr period in tissue sections from avocado (Persea gratissima Gaertn. F., var. Fuerte), both pulp and peel of banana (Musa sapientum L., var. Gros Michel), bean endocarp (Phaseolus vulgaris L., var. Kentucky Wonder Pole beans) and leaves of Rhoeo discolor. Ethylene had no effect on permeability in 4 of the 5 tissues, but sometimes enhanced solute uptake in banana peel; it had either no effect or an inhibitory effect on synthesis of RNA and protein in sections from fruits of avocado and banana. Auxin (alpha-naphthalene acetic acid) stimulated synthesis of RNA and protein in bean endocarp and Rhoeo leaf sections, whereas ethylene inhibited both basal and auxin-induced synthesis. It is concluded that in these tissues the auxin effect is not an ethylene effect.

Abstract  A comparative study was made of the effects of auxin (alpha-naphthalene acetic acid), kinetin (6-furfurylaminopurine) and a mixture of auxin and kinetin applied in vivo on synthesis of RNA and protein and the distribution of such synthesis amongst the subcellular fractions of sections of endocarp from Kentucky Wonder pole beans (Phaseolus vulgaris, L.). Auxin caused considerable enhancement of incorporation of labeled precursors into RNA and protein of all subcellular fractions, and induced net synthesis of RNA and protein. That auxin-induced net synthesis of protein is repressed by actinomycin D indicates that auxin acts primarily to stimulate synthesis of RNA, as a result of which synthesis of protein is enhanced. The effect of kinetin alone on synthesis of RNA, or of kinetin on auxin-induced synthesis of RNA was variable, with either stimulation or inhibition observed in different experiments. Kinetin-enhancement of synthesis of both RNA and protein in subcellular fractions also varied, with enhancement of synthesis in 1 or all subcellular fractions among different experiments. The variable effect of kinetin did not seem to be related to the amount of endogenous or added auxin. The mode of action of kinetin is discussed.

Abstract  The effect of ethylene on the uptake, distribution and polar transport of C(14) from indole-3-acetic acid-2-C(14) and naphthalene acetic acid-1-C(14) in tissue sections was studied. Test species were cotton (Gossypium hirsutum, L.) and cowpea (Vigna sinensis, Endl.). Generally, incubation of tissue or intact plants with ethylene reduced the degree of polar auxin transport. Ethylene inhibited the movement of both auxins in stem tissue and IAA in petiole tissue of cotton. The effect of ethylene on auxin movement in cow-peas was more complex. Ethylene apparently inhibited transport in younger petiole and stem tissue, but stimulated the process to a small but significant degree in basal petiole segments.Ethylene, in some experiments, reduced C(14) (auxin) uptake. This reduction was consistently smaller than the inhibition of transport. Effects upon transport were observed when uptake was not different. Differences in uptake declined as the period of incubation with auxin was lengthened, but transport was inhibited for up to 23 hours.It is proposed that ethylene may, through its effect on transport, cause localized shortages and surpluses of auxin which in turn contribute to symptoms now associated with the response of sensitive species to ethylene.

Abstract  BIOSIS COPYRIGHT: BIOL ABS. This study describes organic compounds in the flue gas of a hazardous waste incinerator. Polycyclic and heterocyclic aromatics, phthalate esters, phosphate esters, halogenated benzenes, biphenyls, naphthalenes, phenols as well as nitro compounds were separated by capillary gas chromatography, characterized and quantified by mass spectroscopy.

Abstract  BIOSIS COPYRIGHT: BIOL ABS. Bottom ash is the main solid residue (in weight) which is produced by municipal solid waste incineration (MSWI) facilities. To be reused in public works, it has to be stored previously a few months. This material is composed primarily of a mineral matrix but also contains unburnt organic matter. The mineral content and its change in the course of aging are relatively well-known, in contrast with the organic content. So in order to detect the phenomena responsible for changes in organic matter an vailable in bottom ash, composed essentially of carboxylic acids and n-alkanes (steroids and PAH's to a lesser extent), and consequently that it would improve the bottom ash quality. Furthermore these results were confirmed by the study of aging conducted in conditions used in the industrial scale (over 12 months).

Abstract  Pulmonary Clara cells are selectively damaged in mice given 1, 1-dichloroethylene (DCE), a chemical used in the plastics industry. The cytotoxicity is attributed to formation of a reactive metabolite believed to be the DCE-epoxide, which was detected in vitro. We have undertaken in vivo studies to test the hypothesis that in situ formation of the DCE-epoxide within Clara cells mediates the cell-specific injury manifested after DCE exposure. Formation of the epoxide was estimated by trapping of the metabolite with glutathione (GSH) and identifying the conjugated products as 2-(S-glutathionyl) acetyl glutathione ([B]) and 2-S-glutathionyl acetate ([C]). High-pressure liquid chromatographic analyses showed that conjugates [B] and [C] were both detected in lung cytosol isolated from mice treated in vivo with [14C]DCE. Epoxide levels in the cytosol, as estimated by the total amount of conjugates formed, were dose-dependent at DCE doses ranging from 25 to 225 mg/kg. Pretreatment of mice with buthionine sulfoximine (BSO) decreased sulfhydryl levels and significantly inhibited the formation of the GSH conjugates. Epoxide levels were also reduced by pretreatment with diallyl sulfone (DASO2), an inhibitor of the P450 isozyme CYP2E1. A polyclonal antibody was developed that is specific for conjugate [C] and that recognizes an antigen consisting of the conjugate epoxide-GSH-glutaraldehyde-bovine serum albumin. Immunohistochemical studies with this antibody revealed staining in Clara cells of mice treated with DCE. Staining was also present in Clara cells of mice treated with both BSO and DCE, but at slightly reduced levels. Reduction of this staining was more pronounced in Clara cells of mice treated with both DASO2 and DCE. These results show that the DCE-epoxide is formed in vivo, is localized in Clara cells, and correlates with the cytotoxicity manifested in this cell type.

Abstract  Reactions of 1,4-naphthalenedicarboxylic acid (1,4-H2nda) and a bent dipyridyl co-ligand 4-amino-3,5-bis(4-pyridyl)-1,2,4-triazole (4bpt) with CoII, ZnII, or CdII acetate afford four coordination polymers, [Co(1,4-nda)(4bpt)(H2O)]n (1), {[Co(1,4-nda)2(4bpt)(H2O)2][Co(4bpt)(H2O)4](H2O)1.5}n (2), {[Zn(1,4-nda)2(4bpt)(H2O)2][Zn(4bpt)(H2O)4](H2O)1.5}n (3), and {[Cd2(1,4-nda)2(4bpt)2(H2O)2](DMF)1.5(H2O)3}n (4). In the structure of the CoII complex 1, the polycatenation of inclined 2-D (4,4) coordination layers leads to the formation of a 3-D supramolecular framework, whereas two types of 1-D polymeric chains are observed in another CoII coordination species 2, which are interconnected via H-bonding to result in an unusual 3-D host-guest lattice. Notably, complexes 1 and 2 have been prepared under similar hydrothermal conditions and their structural discrepancy can only be ascribed to a subtle change of basicity for the reaction solution. The ZnII complex 3 is isostructural to 2, and the CdII complex 4 displays a 2-fold parallel interpenetrating array of undulating (4,4) coordination layers. By using the conventional solvent evaporation method, two PbII naphthalenedicarboxylates [Pb(1,4-nda)(DMF)]n (5) and {[Pb2(2,6-nda)2(DMF)2](DMF)}n (6) have also been prepared (2,6-nda = 2,6-naphthalenedicarboxylate). Complex 5 has a unique 5-connected 3-D coordination architecture, whereas 6 represents a 3-fold interpenetrating framework of 4-connected diamond topology. Their structural difference suggests the significant isomeric effect of the naphthalenedicarboxylate tectons on structural assemblies. Thermal stability of these crystalline materials has been investigated by thermogravimetric and differential thermal analysis (TG-DTA) technique and solid-state luminescent properties of the ZnII, CdII, and PbII complexes have also been explored.

Abstract  Secondary nonferrous production is addressed as one of the potential sources of the unintentionally produced persistent organic pollutants (UP-POPs) due to the impurity of raw material. Although there are inventories of dioxin emissions from secondary nonferrous metallurgical facilities, release inventories of polychlorinated naphthalenes (PCNs) are scarce. This study selected typical secondary copper, aluminum, zinc, and lead plants to investigate the emissions of PCNs in secondary nonferrous production in China. The toxic equivalency (TEQ) emission factor for PCNs released to the environment is highest for secondary copper production, at 428.4 ng TEQ t^-1, followed by secondary aluminum, zinc, and lead production, at 142.8, 125.7, and 20.1 ng TEQ t^-1, respectively. PCNs released in secondary copper, aluminum, lead, and zinc production in China are estimated to be 0.86, 0.39, 0.009, and 0.01 g TEQ a^-1, respectively. Analysis of stack gas emission from secondary nonferrous production revealed that less-chlorinated PCNs are the dominant homologues, with mono- to tri-CNs making the most important contributions to the concentration. However, for fly ash, the more highly chlorinated PCNs such as octa-CN are the dominant homologues.

Abstract  P2X2 receptors are members of the ATP-gated P2X family of cation channels, and they participate in neurotransmission in sympathetic ganglia and interneurons. Here, we identified 7,7'-(carbonylbis(imino-3,1-phenylenecarbonylimino-3,1-(4-methyl-phenylene)carbonylimino))bis(1-methoxy-naphthalene-3,6-disulfonic acid) tetrasodium salt (NF770) as a nanomolar-potent competitive P2X2 receptor antagonist within a series of 139 suramin derivatives. Three structural determinants contributed to the inhibition of P2X2 receptors by NF770: 1) a "large urea" structure with two symmetric phenylenecarbonylimino groups; 2) attachment of the naphthalene moiety in position 7,7'; and 3) the specific position of two sulfonic acid groups (3,3'; 6,6') and of one methoxy group (1,1') at the naphthalene moiety. This structure-activity relationship was interpreted using a rat P2X2 homology model based on the crystal structure of the closed zebrafish P2X4 receptor. Docking of the suramin derivatives into the modeled ATP-binding pocket provides a uniform explanation for the observed differences in inhibitory potencies. Changes in the chemical structure that increase the inhibitory potency of the suramin derivatives improved the spatial orientation within the ATP-binding pocket to allow for stronger polar interactions of functional groups with Gly72, Glu167, or Arg290. Gly72 is responsible for the orientation of the methoxy group close to Arg290 or Glu167. Combined mutational and functional analysis confirmed that residues Gly72 and Glu167 are as important for ATP binding as Arg290, the ATP-binding role of which has been shown in previous studies. The in silico prediction of Gly72 and Glu167 as ATP-binding residues strongly supports the validity of our homology docking.

Abstract  15 hazardous industrial waste samples were evaluated for mutagenicity in the Salmonella plate-incorporation assay using strains TA98 and TA100 in the presence and absence of Aroclor 1254-induced rat liver S9. Dichloromethane/methanol extracts of the crude wastes were also evaluated. 7 of the crude wastes were mutagenic, but only 2 of the extracts of these 7 wastes were mutagenic; extracts of 2 additional wastes also were mutagenic. In addition, 10 of the crude wastes were administered by gavage to F-344 rats, and 24-h urine samples were collected. Of the 10 raw urines evaluated, 3 were mutagenic in strain TA98 in the presence of S9 and β-glucuronidase. The 3 crude wastes that produced these 3 mutagenic urines were, themselves, mutagenic. Adequate volumes of 6 of the 10 raw urines were available for extraction/concentration. These 6 urines were incubated with β-glucuronidase and eluted through Sep-Pak® C18 columns; the methanol eluates of 3 of the urines were mutagenic, and these were the same 3 whose raw urines also were mutagenic. In general, the C18/methanol extraction procedure reduced the cytotoxicity and increased the mutagenic potency of the urines. To our knowledge, this is the first report of the mutagenicity of urine from rodents exposed to hazardous wastes. Based on the present results, the use of only strain TA98 in the presence of S9 might be adequate for general screening of hazardous wastes or waste extracts for genotoxicity. The urinary mutagenesis assay does not appear to be a useful adjunct to the Salmonella assay for screening hazardous wastes. The problems associated with chemically fractionating diverse types of hazardous wastes for bioassay are also discussed.

Abstract  Methods by which rodent carcinogenicity can be predicted have been prospectively validated for 40 chemicals evaluated for carcinogenicity by the US National Toxicology Program. It is concluded that a chemical of unknown carcinogenicity can be predicted to be in one of three possible categories--probably carcinogenic, probably non-carcinogenic or of uncertain activity. The last category is unlikely to contain genotoxic trans-species and/or multiple-site carcinogens. The component parameters of such predictions are one or more of several aspects of chemical structure, genotoxicity and rodent toxicity. Each of these parameters requires refinement but all are developed to the point that they can be integrated to make assessment of possible carcinogenicity. Carcinogenicity tends to be overpredicted by this integrated technique, each part of which has already been simulated by computer modelling. Improvements in predictive methodology will flow from three assumptions: (i) that emphasis must be placed equally on the properties of the test chemical and the responses it elicits in tissues for which carcinogenicity is to be predicted, (ii) that the integration of different predictive technique is preferable to the exclusive use of a single technique, and (iii) that the general predictivity of any technique or combination of techniques appears to be limited to < or = 80%, imposed by inadequate knowledge, and uncertainties in the experimental evaluation and classification of carcinogenic responses for diverse chemicals. This last statement does not preclude the attainment of higher accuracy within a congeneric series of chemicals. Foreknowledge of the likely outcome of a rodent carcinogenicity bioassay is now possible and will contribute to the focusing of animal testing resources.

Abstract  Part of Water Environment Research's annual Literature Review. The activated sludge and other aerobic suspended culture processes subsection of the treatment systems section of the review contains segments on process modeling and kinetics; process microbiology; nitrogen and phosphorus control; fate and effects of xenobiotics; industrial wastes; design, operation, and control; oxygen transfer; and solids separation.

Abstract  The toxicity of 76 priority pollutants to lettuce (Lactuca sativa) was determined in soil and in nutrient solution. In the first case a static and in the latter a semistatic exposure was established Volatile and easily degradable compounds had high EC50 values in soil (> 1,000 μg/g). In nutrient solution, however, several of these compounds were rather toxic. Quantitative structure‐activity relationships (QSARs) relating EC50 values to log Kow could be described for the toxicity in nutrient solution. Generally, the toxicity of the compounds increased with increasing lipophilicity. Deviations were (partly) caused by reactivity (N‐containing compounds, double bonds in compounds), low lipophilicity (log Kow values < 1), and EC50 values close to solubility. To relate toxicity in soil and nutrient solution, soil EC50 values were recalculated to values in the soil pore water using calculated adsorption coefficients. Estimated pore‐water EC50 values showed a good correlation with values determined in nutrient solution but were not equal to these values. The differences can be attributed to differences in exposure (static vs. semistatic).