N-Nitroso compounds produced in deer mouse (Peromyscus maniculatus) GI tracts following hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) exposure

Given the potent carcinogenic effects of most N-nitroso compounds, the reductive transformation of the common explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) to a group of N-nitroso derivatives, hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX), hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (DNX), and hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX) in the environment have caused concerns among the general public. Questions are arising about whether the same transformations also occur in mammals, and if true, to what extent. This study investigated the N-nitroso derivatives production in the deer mouse GI tract following RDX administration. Findings verified that such transformations do occur in the mammalian GI tract at notable levels: the average MNX concentrations in deer mice stomach were 85 microg/kg and 1318 microg/kg for exposure to 10mg/kg and 100mg/kg diet, respectively. DNX in stomach were 217 microg/kg for the 10mg/kg dose group and 498 microg/kg for the 100mg/kg dose group. Changes in other toxic endpoints including body weight gain, food consumption, organ weight, and behavior were also reported.     

Acute effects of Fe₂O₃, TiO₂, ZnO and CuO nanomaterials on Xenopus laevis

Metal oxide nanomaterials have exhibited toxicity to a variety of aquatic organisms, especially microbes and invertebrates. To date, few studies have evaluated the toxicity of metal oxide nanomaterials on aquatic vertebrates. Therefore, this study examined effects of ZnO, TiO₂, Fe₂O₃, and CuO nanomaterials (20-100 nm) on amphibians utilizing the Frog Embryo Teratogenesis Assay Xenopus (FETAX) protocol, a 96 h exposure with daily solution exchanges. Nanomaterials were dispersed in reconstituted moderately hard test medium. These exposures did not increase mortality in static renewal exposures containing up to 1000 mg L⁻¹ for TiO₂, Fe₂O₃, CuO, and ZnO, but did induce developmental abnormalities. Gastrointestinal, spinal, and other abnormalities were observed in CuO and ZnO nanomaterial exposures at concentrations as low as 3.16 mg L⁻¹ (ZnO). An EC₅₀ of 10.3 mg L⁻¹ ZnO was observed for total malformations. The minimum concentration to inhibit growth of tadpoles exposed to CuO or ZnO nanomaterials was 10 mg L⁻¹. The results indicate that select nanomaterials can negatively affect amphibians during development. Evaluation of nanomaterial exposure on vertebrate organisms are imperative to responsible production and introduction of nanomaterials in everyday products to ensure human and environmental safety.     

The role and functioning of environmental assessment: theoretical reflections upon an empirical investigation of causation

Environmental assessment is an intriguing policy phenomenon: it is employed in an ever-increasing range of contexts the world-over, yet research indicates it rarely efficiently or effectively achieves its principal purpose of promoting sustainable development. Increasingly, practical limitations in the effectiveness of environmental assessment are attributed to its theoretical shortcomings, particularly in relation to the conception of causation. This research advanced debate on environmental assessment by examining the theoretical implications of an empirical analysis of its causal operation in purposefully selected cases. The causal models derived from the research data illustrate the diversity of mechanisms through which environmental assessment can contribute to sustainability, and provide an insight into the complexity and contextuality of causation in the empirical realm. The research findings also highlight a multiplicity of societal expectations concerning environmental assessment's contribution to sustainable development. It is concluded that the interplay of non-rational variables (such as power, agency, experiences and expectations) necessitates the pursuit of a reflexive accommodation of purposes, methods and context in environmental assessment practices.     

The Contribution of Environmental Assessment to Sustainable Development: Toward a Richer Empirical Understanding

It has long been suggested that environmental assessment has the potential to contribute to sustainable development through mechanisms above and beyond informing design and consent decisions, and while theories have been proposed to explain how this might occur, few have been subjected to rigorous empirical validation. This research advances the theoretical debate by building a rich empirical understanding of environmental assessment’s practical outcomes, from which its potential to contribute to sustainable development can be gauged. Three case study environmental assessment processes in England were investigated using a combination of data generated from content analysis, in-depth interviews, and a questionnaire survey. Four categories of outcomes are delineated based on the research data: learning outcomes; governance outcomes; attitudinal and value changes; and developmental outcomes. The data provide a robust critique of mainstream theory, with its focus on design and consent decisions. The article concludes with an examination of the consequences of the context-specific nature of environmental assessment practices in terms of developing theory and focusing future research.     

Condition of the Mid-Atlantic Estuaries: Production of a State of the Environment Report

The U.S. Environmental Protection Agency has released a report entitled Condition of the Mid-Atlantic Estuaries. That report summarizes the findings of several studies conducted by federal and state agencies and academic institutions in Chesapeake Bay, Delaware Estuary, and the coastal bays of Delaware, Maryland, and Virginia, and simultaneously addresses two distinct audiences: environmental managers and the general public. This paper documents the process of preparing the Estuaries Report, emphasizing the lessons learned in merging information from a wide-variety of sources and in reporting the results to multiple audiences. The major difficulties in preparing the report included: 1) choosing a format and topics that adequately addressed both environmental managers and the public, 2) resolving spatial and temporal disparities in the assembled data sets, and 3) establishing threshold values that distinguished between acceptable and unacceptable conditions in indicators. Our solutions to these challenges and alternatives are discussed. We conclude that a small team of knowledgeable scientists can effectively merge the information of diverse sources into a document that is useful to both environmental managers and the interested public. However, considerable interaction between the team and other scientists was necessary to resolve ambiguities and assure relevancy and accuracy. These findings support the proposition that the vast sources of existing environmental information can be easily and effectively used to assess the ecological condition across large regions.     

Changes in nucleic acids over the molt cycle in relation to food availability and temperature in Homarus americanus postlarvae

Postlarval lobsters Homarus americanus Milne Edwards hatched from three females collected in 1989 from Block Island Sound, Rhode Island were reared individually in the laboratory under nine treatment combinations of temperature (15, 18 and 21°C) and feeding (starved, low ration and full ration). Total RNA, DNA (mgind.^-1), RNA:DNA ratios and molt stage were determined for individuals sampled at daily intervals. Postlarval lobsters had high resistance to starvation. A majority of the lobsters survive 12 d of food deprivation, with some surviving up to 24–29 d. During starvation, cell biomass (estimated from protein:DNA) decreased to a minumum size, whereas cell number (based on total DNA) was generally conserved. The molt cycle was arrested at molt stage C in the starved postalrvae. Instar duration was inversely related to temperature. However, the duration of the postlarval instar did not differ between the low and full ration treatments. Uncoupling of cell growth and the molt cycle was evident in the full and low ration treatments. In the full ration treatments, the postmolt through early premolt was characterized by a rapid increase in total RNA and DNA. Maximum cell biomass was attained by molt stage C or D₀. In the low ration treatments, total RNA and DNA were less than those in the full ration treatments and the maximum cell biomass was attained only at molt stage D_2-3. Notably, different feeding regimes resulted in different patterns in RNA:DNA ratios over the molt cycle during the postlarval instar. RNA:DNA ratio was a sensitive indicator of recent (2 to 3 d) food deprivation. However, this ratio was positively related to the level of feeding only at molt stages C to D₁ and was inversely related to temperature regime. These results indicate that the use of RNA:DNA ratios to estimate the relative nutritional state of postlarval tobsters must be qualified with respect to the period of the molt cycle and the temperature regime.     

Toxicity of hexahydro-1,3,5-trinitro-1,3,5-triazine to larval zebrafish (Danio rerio)

Hexahydro-1,3,5-trinitro-1,3,5-triazine, a cyclonitramine commonly known as RDX, is used in the production of military munitions. Contamination of soil, sediment, and ground and surface waters with RDX has been reported in different places around the world. Acute and subacute toxicities of RDX have been relatively well documented in terrestrial vertebrates, but among aquatic vertebrates the information available is limited. The objective of this study was to characterize the acute toxicity of RDX to larval zebrafish. Mortality (LC50) and incidence of vertebral column deformities (EC50) were two of the end points measured in this study. The 96-h LC50 was estimated at 22.98 and 25.64 mgl(-1) in two different tests. The estimated no-observed-effective-concentration (NOEC) values of RDX on lethality were 13.27+/-0.05 and 15.32+/-0.30 mgl(-1); and the lowest-observed-effective-concentration (LOEC) values were 16.52+/-0.05 and 19.09+/-0.23 mgl(-1) in these two tests, respectively. The 96-h EC50 for vertebral deformities on survivors from one of the acute lethality tests was estimated at 20.84 mgl(-1), with NOEC and LOEC of 9.75+/-0.34 and 12.84+/-0.34 mgl(-1), respectively. Behavioral aberrations were also noted in this acute toxicity study, including the occurrence of whirling movement and lethargic behavior. The acute effects of RDX on survival, incidence of deformities, and behavior of larval zebrafish occurred at the high end of the most frequently reported concentrations of RDX in aquatic environments. The chronic effects of RDX in aquatic vertebrates need to be determined for an adequate assessment of the ecological risk of environmental RDX.     

Determination of Multiple Atmospheric Diffusion Coefficients Using the Carbon Hollow Tube Gas Chromatography Method

Gaseous organic species were collected by carbon hollow tube pairs. Diffusion coefficients (D_a) of anhydrous and hydrated organic species were then determined by measuring the ratio of each component that adsorbed in the collection tubes. In controlled experiments, the precision and accuracy of D_a determinations were 12 percent and 9.1 percent respectively. Ternary mixtures of airborne compounds were separated and quantified using gas chromatography. Observed D_as for each component of these mixtures were similar to those obtained for individual components. This method was applied to volatile organic species in marine air, soil air, and cigarette effluents.     

Uptake, accumulation and depuration of sodium perchlorate and sodium arsenate in zebrafish (Danio rerio)

In toxicokinetics studies, interactions between chemicals in mixtures has been largely neglected. This study examines a mixture of perchlorate and arsenate because (1) they have the potential to co-occur in contaminated aquatic habitats, and (2) a previous study by the authors found possible toxicological interactive effects. In the present study, zebrafish (Danio rerio) were exposed to two concentrations of sodium perchlorate (10 and 100 mg l(-1)), sodium arsenate (1 and 10 mg l(-1)), and the mixture-sodium perchlorate+sodium arsenate (10+1 mg l(-1) and 100+10 mg l(-1) Na(2)HAsO(4)-high mixture) for 90 d. Their uptake and accumulation by zebrafish was evaluated at 10, 30, 60, and 90 d. In addition, depuration was examined at 1, 3, and 5d after cessation of the exposure. The uptake of either chemical was concentration-dependent, with significantly higher uptake at high concentrations at either exposure interval. In contrast, there was no significant difference in whole body residue between single chemicals and the corresponding mixture except for 100 mg l(-1) sodium arsenate at 90 d. However, there was increasing accumulation over time at the high concentration of either chemical alone and their mixture, and this increasing trend was more pronounced in the single chemical exposures than in the mixture. At the concentrations tested in the current study, both chemicals reduced the uptake but enhanced the depuration of the other chemical from the zebrafish. This study represents the first examination of the interaction of two anions-perchlorate and arsenate with respect to toxicokinetics.     

Comparison of white-footed mice and rice rats as biomonitors of polychlorinated biphenyl and metal contamination

A study was conducted to assess differences in contaminant assimilation among co-occurring white-footed mice (Peromyscus leucopus) and rice rats (Oryomys palustris) captured at a contaminated site. Rodents were collected from five areas at the Paducah Gaseous Diffusion Plant (PGDP), a uranium enrichment facility. Relatively few white-footed mice (8.7%) had quantifiable concentrations of PCBs compared to 42% of rice rats (chi2 = 6.49, d.f. = 1, P < 0.025), and seven of the 11 rice rats (64%) over 50 g body mass had quantifiable concentrations of PCBs in their livers. White-footed mice had higher mean concentrations of barium (P < 0.0001), chromium (P = 0.0010), copper (P = 0.0011), lead (P = 0.0335), and aluminum (P = 0.0006) than rice rats at all five sampling areas. Species-specific differences in accumulation of PCBs and metals were observed and attributed to differences in habitat use and foraging strategies.