Half-lives of tetra-, penta-, hexa-, hepta-, and octachlorodibenzo-p-dioxin in rats,monkeys, and humans--a critical review

The elimination half-lives (t1/2) in Sprague-Dawley rats for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 1,2, 3,7,8-pentachlorodibenzo-p-dioxin (PeCDD), 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin (HxCDD), 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (HpCDD) and 1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin (OCDD) were estimated in long-term studies by Schlatter, Poiger and others. Furthermore, there are some published half-lives of TCDD in adult humans. The average half-life of TCDD in adult humans is approximately 2840 days, while in Sprague-Dawley rats the average t1/2 of TCDD is 19 days. The t1/2 of TCDD in humans is about 150 times that of rats. This factor was used to calculate the t1/2 values of the other polychlorinated dibenzo-p-dioxins (PCDDs) in humans from the rat data. Furthermore, the terminal t1/2 values of PCDDs in adult humans were calculated from the regression equation: logt1/2H = 1.34 logt1/2R + 1.25 which was recently established for 50 xenobiotics (t1/2H = terminal half-lives in days for humans, t1/2R = terminal half-lives in days for rats). The following terminal half-lives in adult humans were obtained: 12.6 years for 1,2,3,7,8-PeCDD, 26-45 years for 1,2,3,4,7,8-HxCDD, 80-102 years for 1,2,3,4,6,7,8-HpCDD and ca. 112-132 years for OCDD. These half-lives of PCDDs are critically compared with measured t1/2 values of PCDDs and other persistent organic pollutants in rats, monkeys and humans.     

High-performance liquid chromatography method for determination of hydrogen peroxide in aqueous solution and application to simulated Martian soil and related materials

A new method for determination of hydrogen peroxide (H₂O₂) is described. H₂O₂ reacts with iodide in the presence of ammonium molybdate and vanillic acid resulting in the formation of iodovanillic acid which is quantified by reversed-phase high-performance liquid chromatography (HPLC) and detected by UV absorption at 280 nm. The method provides a detection limit of ～0.1 μM and is easy to implement. Iodovanillic acid is stable, allowing multiple measurements of the same sample, and the separation power of the HPLC yields high selectivity against potential interferences. This method will be useful for many environmental applications. The method has been applied to quantify the photochemical production of H₂O₂ by aqueous suspensions of various minerals and soils.     

Reproductive cycle of the sea urchin Holopneustes purpurascens (Temnopleuridae: Echinodermata)

This study documents the annual reproductive cycle of the Temnopleurid echinoid Holopneustes purpurascens near Sydney. H. purpurascens reached sexual maturity between 11 and 26 mm diameter and was gonochoristic. The sequence of oogenesis was similar to previously described echinoids. However, the proportion of eggs at each stage showed no temporal pattern in abundance, suggesting that vitellogenesis is continuous throughout the year. Spermatogenesis was also similar to other echinoids and showed a significant increase in the proportion of partially spawned testes in spring, followed by a similar increase in the proportion of partially spawned testes in late spring and summer. Gonad indices showed a peak in weight from late winter to mid-spring (9.10ǃ.47 for females; 6.28ǂ.43 for males; mean-SE), then a decline for both sexes. Although spawning was variable over time, there was a peak in the proportion of spawning from late winter to early summer that correlated with the observed peaks in gonad indices and gametogenic cycles. The demographic implications of this reproductive pattern are that new recruits can enter the population through synchronous spawning during the breeding period, and smaller haphazard spawning events at other times of the year.     

An investigation of aqueous activity coefficients at low concentrations

The activity of a chemical in solution determines its tendency to move into other media. At low concentrations (<0.01M) it is generally considered to be linearly related to concentration. A hypothetical model based on the structure of liquid water is discussed which could cause deviations from this linearity in the ppb region, a concentration much lower than that normally investigated thermodynamically, but one of great importance environmentally. Headspace experiments are reported with carbon tetrachloride and chloroform in water at concentrations down to ～10^?3 ppb but no such deviations were discerned.     

The concentration, apparent molecular weight and chemical reactivity of silica from groundwater in southern Nevada

Sorption of radionuclides, metals and organic compounds to colloidal particles has been suggested to increase the mobility of these pollutants in groundwater. Because silicates and alumino-silicates can be important components of groundwater colloids, we have conducted a study to characterize the nature of silica in various springs and wells in Southern Nevada and to determine the extent that silica may be associated with colloidal particles that can participate in pollutant transport. The total silica content was measured using inductively coupled plasma emission spectroscopy (ICP). In addition, reactive silica was measured using the silica molybdate colorimetric technique. The apparent molecular weight of the silica was investigated using split-flow-lateral-transport-thin-cell-fractionation (SPLITT) which can readily distinguish between colloidal and low molecular weight associations. This study indicates that silica does not tend to form stable inorganic colloids in Southern Nevada groundwaters but exists as low molecular weight species. However, water from one of the test facilities on the Nevada Test Site (NTS) did contain stable siliceous colloids that could have important implications for the modeling the transport of radionuclides at this site.     

PCBs and PCDD/Fs in lake sediments of Grosser Arbersee, Bavarian Forest, South Germany

Despite their environmental importance, there are still relatively few historical studies of the environmental occurrence of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), especially in middle Europe. Trends in PCBs and PCDD/Fs were, therefore, assessed in lake sediments of the Grosser Arbersee over the past 130 years (1860-1990). Ballschmiter-PCB concentrations (congeners # 28, 52, 101, 138, 153, 180) increased between 1946 and 1972 from 4.2 to 32.0 microg kg(-1) dry wt, but have since decreased to 25.6 microg kg(-1) dry wt. High chlorinated PCB congeners reached their maxima earlier (1968-1972) than low chlorinated congeners (1985-1991). These trends were consistent with patterns expected from the production and use of PCBs and their precursors. PCDD/F concentrations increased between 1950 from 0.6 microg kg(-1) dry wt to 2.3 microg kg(-1) dry wt in 1977, falling to 1.7 microg kg(-1) dry wt by 1993. PCDF concentrations exceeded those of PCDD until 1968, but afterwards PCDDs (especially OCDD) were predominant. These patterns suggest that domestic heating and waste combustion were the most likely sources, but pollution from local industries, such as metal smelting and glass production, might also have been involved. The data provide a valuable case study from central Europe which confirms the overall declining trends of PCB and PCDD/F contamination shown elsewhere.     

The suitability of gastropods as biomarkers

The measurement and induction of mixed function oxyigenases (MFOs) of limnetic gastropods were investigated to estimate their suitability as biomarkers. A determination of MFO activities was performed through the measurement of ethoxyresorufin-O-dealkylase (EROD), pentoxy-(PROD) and benzoxyresorufin-O-dealkylase-activity (BROD). Optimal measuring conditions of these activities were investigated in preparations of the digestive gland of 4 species of limnetic gastropods. Results indicate that MFO-activity inhibiting substances are accumulating in the microsomal pellet, the fraction commonly used for the measurement of MFO-activities. Therefore, the fraction used for induction studies was the postmitochondrial supernatant (PMS). EROD, PROD, and BROD activity ofPlanorbis planorbis andPlanorbis carinatus were measured after a treatment with Aroclor 1254 for 1–17 days. Maximal induction of EROD and PROD were 6 and 10 times the value in the control group ofP. carinatus, respectively induction inP. planorbis was lower. BROD-activity could not been measured inP. planorbis. InP. carinatus, BROD-activity increased to a maximum of 2 times after traetment with Aroclor 1254. The level of induction of EROD-activity is comparable to results described in analog studies with fish.     

Partielle Ordnung

Zusammenfassung  Sollen Chemikalien oder Umweltbelastungen ?kotoxikologisch beurteilt werden, so erfordert die Komplexit?t ?kosystemarer Zusammenh?nge, da? Bewertungsverfahren Informationen m?glichst nicht aggregieren soilten. Es gibt keine ?kologisch begründete, allgemein verwendbare Zielfunktion. Die Technik, dennoch beispielsweise Chemikalien miteinander vergleichen zu k?nnen, beruht auf der Verallgemeinerung des Ordnungsbegriffs und der Visualisierungsmethode durch Hasse-Diagramme. Am Beispiel von sechs Chemikalien wird das Verfahren erl?utert und gezeigt, da? ungünstige Einstufungen von Chemikalien verschiedene Ursachen haben k?nnen, die dann auch unterschiedliche ?kotoxikologische Konsequenzen bewirken.      

Einsatz der Hasse-Diagrammtechnik zur vergleichenden Bewertung von aquatischen Wirkungstests

In eine ?kotoxikologische Bewertung von Schadstoffen müssen die Ergebnisse von Wirkungstests einflie?en. Die Qualit?t der Bewertung im ?kosystemaren Kontext steht und f?llt mit der ?kosystemaren Qualit?t der Tests. In der vorliegenden Arbeit wird eine Bestandsaufnahme aquatischer Wirkungstests (unabh?ngig von bestehenden legislativen Vorgaben) vorgenommen, und es werden die Ergebnisse in einer Tabelle zusammengestellt, die Einsatzbereiche, Anwendbarkeit für mathematische Wirkungsmodellierung und ?kosystemare Relevanz enth?lt. Die hieraus resultierende Tabelle ist schwer zu überblicken und Zusammenh?nge zwischen bestimmten Wirkungstests sind kaum überschaubar. So ist auch eine Einstufung der aquatischen Wirkungstests ohne zus?tzliche mathematische Hilfsmittel schwierig. Hier wird gezeigt, wie anhand der Technik derHasse-Diagramme die Einstufung der Wirkungstests nach ihrer Qualit?t erleichtert wird. Es zeigt sich u.a., da? es keinen Test gibt, der alle Anforderungen gleichzeitig erfüllt. Einerseits gibt es sechs Tests, die — nach ihren Einsatzbereichen und nach ihrer Umsetzbarkeit für die mathematische Modellierung beurteilt — zwar optimal sind, aber keine ?kosystemare Relevanz aufweisen. Andererseits gibt es zwei Tests, die besonders ausgezeichnet sind: Einer (Test 8), der drei Einsatzbereiche aufweist und gleichzeitig sowohl für die mathematische Modellierung geeignet, als auch ?kosystemar relevant ist, und einer, der in zwei anderen Einsatzbereichen positiv beurteilt wurde und noch ?kosystemar interessant ist (Test 54). Es zeigt sich, da? zwischen Tests mit breitem Einsatzbereich und solchen, die ?kosystemar relevant sind, eine Lücke klafft. An evaluation of pollutants depends on the ecotoxicological quality of the effect tests carried out. In this paper a compilation of aquatic tests is given independently on administration needs. The results are summarized in a table listing fields of application, importance for mathematical modelling and ecological relevance. The table includes 55 tests and 8 attributes characterizing each tests The interpretation of the results listed in this table is hardly feasible. An appropriate tool to rank the tests is the technique ofHasse-diagrams. Using this tool it can be deduced that no test fulfills all demands. There are six tests which are optimal with respect to applicability and mathematical modelling. However, they have no relevance for ecosystems. Only two tests are optimal with respect to ecotoxicology, There is still a gap between tests with a wide field of applications and those tests which are relevant with respect to ecotoxicology.