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Archives of Environmental Contamination and Toxicology (v.49, #1)
The Ratios of Individual Chemicals in a Mixture Determine the Degree of Joint Effect: The Climax Hypothesis by Z. Lin; Z. Ping; D. Kong; K. Yin; Z. Cai (pp. 1-8).
A new hypothesis, the Climax Hypothesis, is proposed to describe how the ratios of individual chemicals influence the joint effects of chemical mixtures. This hypothesis is derived from a generalized approach using “isobolograms.” With this hypothesis, one can predict that for a given mixture, a curvilinear correlation exists between the joint effects and the ratios of individual chemicals and that this curve has a climax at the equitoxic ratio. This prediction is supported by the observed toxicity to Vibrio fischeri of 18 mixtures (12 binary mixtures, 4 ternary mixtures, and 2 quaternary mixtures). With this prediction, the Climax Hypothesis has some promising applications such as controlling the discharge of effluents in environmental science, maximizing detoxifying effects in medicine, and optimizing combined pesticides in agriculture.
Fate of Triclosan and Triclosan-Methyl in Sewage TreatmentPlants and Surface Waters by Kai Bester (pp. 9-17).
The fate of triclosan in diverse stages of two sewage treatment processes has been determined. The elimination process differed considerably depending on the technology applied in the respective sewage treatment plant (STP). The plant operating with a two-stage biologic (activated sludge) process removed triclosan more efficiently than the STP with a combination of physical and activated sludge process. The treatment in the aeration basin was the dominant elimination mechanism, whereas the final biologic filter was not very effective. The elimination rates for triclosan were 87% and 95%, respectively. These data were compared with emissions of a multitude of STPs in the river Ruhr catchment area as well as triclosan and its known transformation product, triclosan-methyl, in the river. The concentrations of both compounds were between <3 and 10 ng/L in true surface-water samples for triclosan and between 0.3 and 10 ng/L for triclosan-methyl. The STP effluents held higher concentrations (10 to 600 ng/L triclosan). The ratio of triclosan to triclosan-methyl did not change significantly within the longitudinal profile of the river, but diverse STPs discharging to the river exhibited individual triclosan–to–triclosan-methyl ratios. From the riverine concentration data, in-river elimination rates and half-life were estimated.
Toxicological Guidelines for Monocyclic Nitro-, Amino- and Aminonitroaromatics, Nitramines, and Nitrate Esters in Drinking Water by K.- M. Wollin; H. H. Dieter (pp. 18-26).
In order to secure a safe drinking water supply, the setting of tolerable/acceptable ceilings of drinking water hygiene is required with regard to xenobiotics resulting from several anthropogenic impacts. This is done in practice by using drinking water guidelines or standards as quantitative objectives. The list of the new EU Directive or the German drinking-water standards is limited to those parameters that have the highest relevance for drinking water quality; nitro compounds (NCs) are not regulated. Because other substances contained in water can also represent a hazard for human health, the German Drinking Water Ordinance clarifies that specific actions must be implemented if compounds other than those regulated appear at concentrations that may be a cause for concern regarding human health. NCs serve as intermediates for dyes, pharmaceuticals, and synthetic materials; they themselves are used as solvents, explosives, and pesticides. During their commercial production or from their use, they may be released to the environment and lead to a contamination of aquatic systems and thus also of drinking water resources. In practice, therefore, a need for assessment is frequently given for relevant NCs. For 19 nitro-, amino-, and aminonitroaromatics, nitramines, and nitrate esters health-based drinking water guide values have been derived. For toxicological evaluation and derivation of guideline values for the NCs of interest, the tolerable daily intake approach was used for chemicals exhibiting a threshold for toxic effects. This was done by using established tolerable body doses for humans based on an identified no-observed-adverse-effect level/low-observed-effect-level for the most sensitive indicator for toxicity. In the case of nonthreshold chemical substances, suitable estimates of excess lifetime cancer risk have been applied.
Kinetics of Degradation of Hydrocarbons in the Contaminated Soil Layer by S Rončević; B Dalmacija; I Ivančev-Tumbas; J Tričković; O Petrović; M Klašnja; J Agbaba (pp. 27-36).
This work presents kinetic parameters of the removal of hydrocarbons in the course of bioremediation of the soil contaminated with crude and oil derivatives, with special emphasis paid to polycyclic aromatic hydrocarbons. Bioremediation was carried out on a laboratory scale, with continuous and discontinuous recirculation of water through the soil column inoculated with the adapted bacterial population. Biodegradation of hydrocarbons can be described by the following equation—ln C = ln C0 – kt—which is most often used in the literature to describe degradation of hydrocarbons, and by the equation—ln C = ln C0 − kt0.5—which is determined on the basis of experimental data (except for pyrene and chrysene, for which a linear equation was used). A comparison of the two models showed a significant difference in the calculated remediation times, indicating that it is not realistic to expect a simple kinetic model to provide precise and accurate descriptions of concentrations during different seasons and in different environments. The results indicated that once contaminated with hydrocarbons, soil can be slowly brought to the previous state provided that no new contamination has occurred.
Residues of Organic Chlorinated Pesticides in Agricultural Soils of Beijing, China by Y. Shi; F. Meng; F. Guo; Y. Lu; T. Wang; H. Zhang (pp. 37-44).
Concentration of organic chlorinated pesticides (OCPs) were measured in topsoils of a selected farm (NK farm) in Beijing in 1993 and 2003. The results indicated that OCPs, mainly 1,2,3,4,5,6-hexachlorocyclohexane (HCH) and 1,1,1,-trichloro-2,2-bis(p-chlorophenyl) ethane (DDT), degraded greatly in the 20 years after the prohibition of their use. DDT was the major contributors of pollution on the farm with 92.23% and 81.28% contributions of total OCP load in soils in 2003 and 1993 respectively. The levels of total DDT and HCH in the old orchard group, in which cultivation began in 1962, were significantly higher (p < 0.05) than those in the new orchard group in which cultivation began in 1991, and all data were higher than the level of barren land (p < 0.05). Studying the isomeric and parent substance metabolite ratios indicated there was more application and accumulation of DDT in the old orchard and that DDT in the new orchard had undergone a different degradation time period or perhaps had been applied more recently, but no new input of HCH was detected. Pollution potential was assessed on the basis of China Soil Environmental Quality Standard.
Quantitative Ultrastructure of Metal-Sequestering Cells Reflects Intersite and Interspecies Differences in Earthworm Metal Burdens by A J Morgan; M P Turner (pp. 45-52).
Morphometric analysis of transmission electron micrographs was used to compare the effects of metals on the multifunctional, metal-sequestering, chloragocyte cells of two epigeic earthworm species, Dendrodrilus rubidus and Lumbricus rubellus, inhabiting three field soils: a clean circumneutral reference soil (Dinas Powys); an acidic moderately Pb- and Zn-contaminated soil (Cwmystwyth); and a calcareous Cd-, Pb-, and Zn-contaminated soil (Draethen). The main findings were: (1) D. rubidus accumulated significantly higher tissue Cd and Pb and lower Zn concentrations than L. rubellus, especially at Draethen; (2) the volume fraction of chloragosomes was significantly lower and the volume fraction of debris vesicles significantly higher in D. rubidus from Draethen compared with L. rubellus at all sites and with the other two D. rubidus populations; (3) estimated relative toxicity factors, derived from soil metal concentrations and published EC50 data, suggested that the subcellular changes in chloragocytes, particularly in D. rubidus from Draethen, were caused mainly by Zn and Pb exposures; (4) scrutiny of the body burdens of each metal in both worm species across the three sites indicated that Cd was a major contributor to the structural changes observed in Draethen D. rubidus, and its impact was disproportionate to its soil and tissue concentrations in comparison with those of Pb and Zn. The apparent greater susceptibility of D. rubidus cells, compared with L. rubellus cells, to soil metal contaminants is discussed in light of differences in the quality and quantity of the metal body burdens accumulated by the two species. Further histopathalogic and morphometric studies on key organs and tissue of earthworms are required to provide biomarkers of exposure and to underpin linkage of biochemical-level changes and demography.
Endocrine Effects in Gammarus fossarum (Amphipoda): Influence of Wastewater Effluents, Temporal Variability, and Spatial Aspects on Natural Populations by M. Schirling; D. Jungmann; V. Ladewig; R. Nagel; R. Triebskorn; H.-R Köhler (pp. 53-61).
In a field study, individuals of autochthounous populations of the amphipod Gammarus fossarum were examined for their maturity status, oocyte development, and biochemical parameters associated with their reproductive cycle. Variability in these parameters was related to abiotic exposure parameters varying in accordance to wastewater discharges, stream identity, and time. Patterns of all investigated parameters showed predominantly seasonal rather than spatial influence for both exposure and biologic effects. Single selected-effect parameters, however—such as the maturity index, late vitellogenic oocyte size and atresia, and the hsp90 level—responded to a sewage treatment plant discharge showing an estrogenic potential and also correlated significantly with the concentration of potential xenoestrogens at the different locations.
Seasonal Variability of Metallothioneins, Cytochrome P450, Bile Metabolites and Oxyradical Metabolism in the European Eel Anguilla anguilla L. (Anguillidae) and Striped Mullet Mugil cephalus L. (Mugilidae) by Stefania Gorbi; Chiara Baldini; Francesco Regoli (pp. 62-70).
The European eel Anguilla anguilla (Anguillidae) and the striped mullet Mugil cephalus (Mugilidae) are typical inhabitants of Mediterranean brackish lagoons, and their utility as bioindicator organisms has already been suggested. The seasonal variability of several potential biomarkers was investigated during a field study carried out in the Orbetello lagoon (Tuscany, Italy). Organisms were sampled on a seasonal basis, and analyzed parameters included the levels of hepatic metallothioneins, the activity of cytochrome P450 1A (EROD), and the presence of biliary PAH metabolites. Special attention was also paid to antioxidant defenses, including catalase, glutathione peroxidases, glutathione reductase, glutathione S-transferases, and total glutathione concentration. Total Oxyradical Scavenging Capacity (TOSC-assay) was measured as an indication of the overall biological resistance to toxicity of different forms of oxyradicals (peroxynitrite, peroxyl and hydroxyl radicals). Obtained results suggest that natural variations of analyzed responses are associated with seasonality of both environmental and biological factors, mainly temperature and reproductive cycle which, however, have a different influence in these two species. Striped mullets exhibited the strongest variations in October when spawning occurs; eels are not influenced by a seasonal sexual maturation and showed more marked changes during the summer, likely related to the elevated seawater temperature and light irradiance in the lagoon. This study confirms the importance of characterizing seasonal variations and the influence of different factors on biological responses that can be used as biomarkers in monitoring programs.
Effects of Dietary Selenomethionine on Larval Rainbow Trout (Oncorhynchus mykiss) by D. Vidal; S. M. Bay; D. Schlenk (pp. 71-75).
Increased selenium (Se) concentrations in water (>10 μg/L) have been measured in the San Diego Creek, which is a tributary of the Upper Newport Bay in Orange County, CA. The objective of this study was to develop tissue- and dietary-based thresholds for Se in resident fish species in San Diego Creek. A 90-day dietary experiment was conducted to determine the effects of seleno-L-methionine (SeMe) on the growth, survival, and whole-body Se accumulation in larval (24-day-old) rainbow trout. Decreased and oxidized glutathione (GSH-to-GSSG ratio) and thiobarbituric acid–reactive substances (TBARS) were also measured in livers of exposed animals to assess oxidative damage caused by Se. Fish food was spiked with SeMe to contain 4.6, 12, and 18 μg/g (dry weight) of Se. Fish exposed to SeMe for 90 days exhibited a significant decrease in body weight and fork length in the 4.6 and 12 μg/g Se treatments compared with controls. Whole-body total Se concentrations increased significantly in fish fed 12 and 18 μg/g SeMe after 90 days compared with controls. Lipid peroxidation (TBARS) and GSH-to-GSSG ratios were unchanged by SeMe treatment. Based on decreased growth after 90 days, a dietary Se lowest observed-effect concentration (LOEC) value of 4.6 μg/g and a Se body burden LOEC of 1.20 μg/g (wet weight) were estimated.
Concentrations of Cadmium, Lead, and Zinc in Fish from Mining-Influenced Waters of Northeastern Oklahoma: Sampling of Blood, Carcass, and Liver for Aquatic Biomonitoring by William G. Brumbaugh; Christopher J. Schmitt; Thomas W. May (pp. 76-88).
The Tri-States Mining District (TSMD) of Missouri (MO), Kansas (KS), and Oklahoma (OK), USA, was mined for lead (Pb) and zinc (Zn) for more than a century. Mining ceased more than 30 years ago, but wastes remain widely distributed in the region, and there is evidence of surface- and groundwater contamination in the Spring River-Neosho River (SR-NR) system of northeastern OK. In October 2001, we collected a total of 74 fish from six locations in the SR-NR system that included common carp (Cyprinus carpio), channel- and flathead catfish (Ictalurus punctatus and Pylodictis olivaris), largemouth- and spotted bass (Micropterus salmoides and Micropterus punctulatus), and white crappie (Pomoxis annularis). We obtained additional fish from locations in MO that included three reference sites and one site that served as a “positive control” (heavily contaminated by Pb). Blood, carcass (headed, eviscerated, and scaled) and liver (carp only) samples were analyzed for cadmium (Cd), Pb, and Zn. Our objectives were to assess the degree to which fish from the OK portion of the SR-NR system are contaminated by these elements and to evaluate fish blood sampling for biomonitoring. Concentrations of Cd and Pb in carp and catfish from OK sites were elevated and Pb concentrations of some approached those of the highly contaminated site in MO, but concentrations in bass and crappie were relatively low. For Zn, correlations were weak among concentrations in the three tissues and none of the samples appeared to reflect site contamination. Variability was high for Cd in all three tissues of carp; differences between sites were statistically significant (p < 0.05) only for blood even though mean liver concentrations were at least 100-fold greater than those in blood. Blood concentrations of Cd and Pb were positively correlated (r2 = 0.49 to 0.84) with the concentration of the same element in carp and catfish carcasses or in carp livers, and the corresponding multiple regression models were highly significant (p ≤ 0.001). Our data indicate that potentially nonlethal blood sampling can be useful for monitoring of selected metals in carp, catfish, and perhaps other fishes.
Chlorinated Hydrocarbon Contaminants and Stable Isotope Ratios in Pelagic Seabirds From the North Pacific Ocean by J E Elliott (pp. 89-96).
Organochlorine pesticides, polychlorinated biphenyls (PCBs), and stable isotopes of nitrogen (δ15N) and carbon (δ13C) were determined in livers of eight seabird species (Diomedea immutabilis, D. nigripes, Fulmarus glacialis, Puffinus bulleri, P. carneipes, P. griseus, P. tenuirostris, and Fratercula corniculata) collected opportunistically from an experimental fishery in the North Pacific Ocean. Concentrations of P, P′-DDE were found in all samples but were highly variable among species, ranging over >2 orders of magnitude from 1.23 mg/kg (wet weight) in D. nigripes to 0.008 mg/kg in P. tenuirostris, whereas total PCBs ranged from 1.14 to 0.020 mg/kg in those same two species. Residues of hexachlorobenzene, trans-nonachlor, photo-mirex, mirex, β-hexachlorocyclohexane, oxychlordane, and heptachlor expoxide were quantified at lower concentrations in all samples. There were significant positive regressions of lipid-normalized concentrations of DDE (r2 = 0.526), total PCBs (r2 = 0.566), CB-153 (r2 = 0.565), and mirex (r2 = 0.586) on the hepatic δ15N signature, indicating that trophic level accounted for approximately 50% of the variability in those contaminants among species. In some species, e.g., P. bulleri, concentrations were lower than expected based on δ15N, which was attributed to a dietary switch before sampling and therefore lack of concordance in the time scales integrated by hepatic chlorinated hydrocarbon concentrations compared with δ15N.
Lead Concentrations in Ruffed Grouse, Rock Ptarmigan, and Willow Ptarmiganin Québec by J Rodrigue; R McNicoll; D Leclair; J.-F Duchesne (pp. 97-104).
Between 1996 and 1998, ruffed grouse, spruce grouse, willow ptarmigan, and rock ptarmigan harvested by hunters in Québec were examined for lead contamination. On examination of the gizzards of these birds, lead shot was found only in ruffed grouse (1.2%). The probability of ingestion of lead shot by grouse and ptarmigans is low. Analyses of the lead concentrations in the wing bones of grouse and ptarmigans and in the muscle tissue of ptarmigans were conducted. Although differences were observed between individuals based on age and sex, the mean concentrations measured were in the range of those that occur naturally at background levels (<6 μg/g dw). Lead concentrations in muscle tissue were low, often at the limit of detection. However, the few high concentrations detected were probably related to a lead pellet or bullet fragment. Based on an analysis of the health risk associated with consumption of ptarmigan muscle, we conclude that the use of lead ammunition for hunting gallinaceous birds may pose an unnecessary risk of lead poisoning because of the possible ingestion of lead shot, bullets, fragments or embedded shot.
Time- and Tissue-Dependent Polychlorinated Biphenyl Residues in Hairless Mice After Exposure to Polychlorinated Biphenyl-Contaminated Soil by K. Imsilp; L. Wiedenmann; G. O. Bordson; C. K. Morrow; R. Cope; L. G. Hansen (pp. 105-118).
Four groups of 16 age-matched female Crl:SKH1-hrBR hairless mice were exposed to either control soil or polychlorinated biphenyl (PCB)–contaminated soil (retrieved from an electrical waste landfill in Southern Illinois) for 11 weeks. The mice were exposed in a study to determine interactions between environmental PCBs and ultraviolet radiation (UVR), but the UVR group did not differ and provided a replicate for the residue study. Ear biopsies were performed immediately after the termination of soil exposure. The mice were maintained in regular bedding for 37 weeks thereafter. The ear-skin, trunk-skin, fat-pad, and liver samples were collected and weighed at the end of the study (week 48) and analyzed for PCB residues. A total of 141 PCB congeners were target analytes. There were significant differences in body weights and food consumption from week 2 to 28. The liver weights of mice treated with PCB only were significantly greater than those of UVR-treated mice. The fat-pad weight did not differ among treated groups. PCB residues in the ear biopsies specimens of mice exposed to contaminated soil were 342.3 and 317.2 ppm in the PCB- and PCB + UVR–treated groups, respectively, and contained both persistent and episodic congeners. After 37 weeks of isolation from soil, the ear PCB residues decreased to 21.5 ppm (PCB group) and 14.5 ppm (PCB + UVR group), and only persistent congeners contributed to the total PCB residues. The accumulation of PCB residues was highest in the fat pad (fat pad > ear skin > trunk skin > liver) in both PCB ± UVR groups at the end of the study. However, the percentage of individual congeners contributing to total PCBs in these different tissues did not differ.
Effects of N-Acetylcysteine on Lead-Exposed PC-12 Cells by Nukhet Aykin-Burns; Elizabeth A. Franklin; Nuran Ercal (pp. 119-123).
The neurotoxicity of lead has been well established through numerous studies. However, the cellular processes of lead neurotoxicity, as well as techniques to prevent or reverse cellular damage after lead exposure, remain unknown. If oxidative stress plays a primary role in lead-induced neurotoxicity, antioxidants should assist in reviving lead-exposed cells. The present study explores N-acetylcysteine (NAC) as an antioxidant agent in PC-12 cells after lead exposure. Selective oxidative stress parameters, including glutathione (GSH), glutathione disulfide (GSSG), and malondialdehyde (MDA), were measured in PC-12 cells exposed to various concentrations of lead acetate. Administering NAC after lead exposure improved cell survival as measured by Trypan Blue exclusion. NAC treatment also increased the GSH/GSSG ratio compared to the lead-only group, and reduced MDA to near control levels. These results imply that NAC protects cells from lead-induced oxidative damage by boosting the PC-12 cells’ antioxidant defense mechanisms.
Survey of Human Exposure to PCDDs, PCDFs, and Coplanar PCBs Using Hairas an Indicator by T. Nakao; O. Aozasa; S. Ohta; H. Miyata (pp. 124-130).
Our environment is polluted with toxic compounds including polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (Co-PCBs). We investigated the suitability of hair analysis for testing human exposure to toxic compounds. Hair analysis revealed that municipal solid-waste (MSW) incineration workers were exposed to PCDDs, PCDFs, and Co-PCBs at high levels. The total 2,3,7,8-TCDD toxic equivalent concentration in MSW incineration workers was 2.5 times higher than in the general population, thus indicating that the indoor environment of the incineration facility was more polluted than the general environment. There were also characteristic patterns of occurrence of these dioxin-like compounds in the hair of smokers from the general population. We confirmed that hair analysis is useful for evaluating human exposure to PCDDs, PCDFs, and Co-PCBs in the atmosphere.
Polychlorinated Dibenzo-p-Dioxins, Polychlorinated Dibenzofurans, and Coplanar Polychlorinated Biphenyls in Human Milk in Osaka City, Japan by T Nakatani; K Okazaki; S Ogaki; K Itano; T Fujita; K Kuroda; G Endo (pp. 131-140).
Forty-eight human milk samples were collected from primiparous mothers in Osaka City from June 1999 to January 2000 and analyzed for polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like coplanar polychlorinated biphenyls (CoPCBs). Mean toxic equivalents (TEQs) in the milk were 13.86 pg I-TEQ/g fat or 16.50 pg World Health Organization (WHO)-TEQ/g fat for PCDDs and PCDFs; 9.87 pg WHO-TEQ/g fat for CoPCBs; and 23.74 pg TEQ/g fat using I-TEQ values of PCDDs and PCDFs or 26.36 pg TEQ/g fat using WHO-TEQ values of PCDDs and PCDFs for total PCDDs, PCDFs, and CoPCBs. The TEQ levels of these chemicals in human milk in Osaka City were in the range of levels in human milk surveyed in Japan, but the TEQ levels of PCDDs and PCDFs and total PCDDs, PCDFs, and CoPCBs from our study were slightly higher than average TEQ levels in human milk in Japan. When comparing our data with the latest data from the United States and some European countries, the TEQ levels of PCDDs and PCDFs in human milk from Osaka City were relatively high, whereas those of CoPCBs were ranked as being of intermediate level. Only TEQ values of CoPCBs in human milk were found to correlate with the increasing age of mothers and their estimated intake of seafood during the year before pregnancy. Concentrations of PCBs 105 and 118 contributed to TEQ values of CoPCBs associated with seafood intake, whereas those of PCBs 156, 157, 114, 189, 167, and 169 contributed to TEQ values of CoPCBs associated with increasing maternal age.